Chemical Analyses for 

Selected Minor Elements 

in Pierre Shale

GEOLOGICAL SURVEY PROFESSIONAL PAPER 391-A
Chemical Analyses for 

Selected Minor Elements 

in Pierre Shale

By L. F. RADER and F. S. GRIMALDI

ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE 

PIERRE SHALE

GEOLOGICAL SURVEY PROFESSIONAL PAPER 391-A

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1961
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEW ART L. UDALL, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington 25, D.C.
CONTENTS

Abstract--_________________________________________

Introduction ___-----_-_--_________________-__--__-_

General remarks._________________________ ______

Laboratories. -._---____-_-______________________

Acknowledgments. ___-_-_-_--______--_-_________

Division of work________________________________

Methods selected and treatment of data ___________

Sample preparation _________________________________

Methods for the determination of individual constituents. 

Titanium. . _____________________________________

Peroxide method._--_--_-____._____________

Alternative tiron method, ___________________

Vanadium. _--.---_____-_-___.__________________

Fusion-leach separation method. _____________

Alternative cupferron separation method.......

Chromium, fusion-leach chromate method _ ________

Manganese, persulfate oxidation method.__________

Cobalt, dithizone-nitroso-R-salt method ___________

Nickel, dimethylglyoxine method _________________

Persulfate oxidation.________________________

Alternative bromine oxidation._______________

Copper, lead, and zinc...-_______________________

Isolation by extraction._____________________

Copper._-__-_____--.___--_________________

Dithiuone method ______________________

Alternative 2, 2' biquinoline method. _____

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Methods for the determination of individual 

constituents Continued

Copper lead, and zinc Continued

Zinc, dithizone method._____^_______________ A-20

Lead, dithizone method______------_-____-__- 22

Arsenic.___________,__________-_-_--___-__---_- 23

Acid digestion, heteropoly blue method________ 23

Alternative fusion-heteropoly blue method_____ 24

Selenium, distillation, visual-estimation method.____ 25

Molybdenum and tungsten______-____------_---_- 27

Isolation by method 1, alpha-benzoinoxime precipitation. ___----_-_-_-__--_----_-----_-- 27

Isolation by alternative method 2, alpha-benzoinoxime extraction ______________________ 28

Isolation of molybdenum by alternative method

3, cupferron separation.___________________ 29

Uranium, fluorometric method.________----__-___. 31

Carbon__-.___.--------------_-----------_----_ 33

Carbonate carbon, gasometric determination--- 33 

Total carbon, gasometric determiilation _______ 37

Determinations of organic carbon.____________ 38

Organic matter.________________--__-_____--_-_- 39

Summary.._________________-__--__--____---_------ 41

Literature cited___________----_-___-___---___--_-_- 44

ILLUSTRATIONS

Page 

FIGURE 1. Comparison of titanium determinations of B

with those of A, C + D, F, and G______ A-6

2. Comparison of vanadium determinations of A

with those of AI, A2 , and B____________. 9

3. Comparison of chromium determinations of B

with those of A, F, and G_______________ 11

4. Comparison of manganese determinations of

A with those of B, C + D, and F________ 13

5. Comparison of cobalt determinations of B

with those of A, AI, F, and G...________ 15

6. Comparison of nickel determinations of A

with those of B and F__________________ 17

7. Comparison of copper determinations of B

with those of A, AI, A2 , A3 , and A4 _____._ 20

8. Comparison of zinc determinations of B with

those of A, AI, and A2 __________________ 21

9. Comparison of lead determinations of B with

those of A and AI________._____________ 22

10. Comparison of arsenic determinations of A

with those of B and B! _________________ 24

Page 

FIGURE 11. Comparison of selenium determinations of A

with those of B and BI__.__._..__.----- A-26

12. Comparison of molybdenum determinations 

of A with those of B______-_-_____-_---

13. Comparison of uranium determinations of B 

with those of BI and A__----_-_--------

14. Apparatus for gasometric determination of 

carbon dioxide- ____________-_--__---_-

15. The relation between the percentage of carbon dioxide in the sample and its volume 

at standard conditions._______________

16. Comparison of carbonate carbon determinations of A with those of AI and of C + D_

17. Comparison of total carbon exterminations of 

A with those of A2 _ _____ A-------------

18. Comparison of organic carbon determinations 

of A with those of Aj___-__-___-__---_-

19. Comparison of organic-matter determinations of E with those of A_______________ 40

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in
IV CONTENTS

TABLES

TABLE 1. Determinations of titanium by different laboratories _______________________________

2. Determinations of titanium in hidden splits 

by three laboratories.___________________

3. Determinations of titanium in check samples.

4. Replicate determinations of vanadium ______

5. Determinations of vanadium in hidden splits. _

6. Determinations of vanadium in check samples. _________________________________

7. Comparision of vanadium recovery by two 

methods when iron content (Fe2 03) of shale 

is less than 5 percent___________________

8. Replicate determinations of chromium____ __

9. Determinations of chromium in hidden splits. _

10. Determinations of chromium in check samples. __________________________________

11. Determinations of manganese by three laboratories _______________________________

12. Determinations of manganese in hidden 

splits _________________________________

13. Determinations of manganese in check 

samples _______________________________

14. Replicate determinations of cobalt- ________

15. Determinations of cobalt in hidden splits_-_-

16. Determinations of cobalt in check samples, __

17. Replicate determinations of nickel-_________

18. Determinations of nickel in hidden splits- ____

19. Determinations of nickel in check samples.

20. Replicate determinations of copper_________

21. Determinations of copper in hidden splits.

22. Determinations of copper in check sampleS-__

23. Replicate determinations of zinc____________

24. Determinations of zinc in hidden splits.-

25. Determinations of zinc in check samples,_

26. Replicate determinations of lead-___________

27. Determinations of lead in hidden splits--

28. Determinations of lead in check samples.-___

29. Replicate determinations of arsenic _________

30. Determinations of arsenic in hidden splits____

31. Determinations of arsenic in check samples. _.

32. Replicate determinations of selenium. ______

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Determinations of selenium in hidden splits. _ - A-26 

Determinations of selenium in check samples-- 27 

Replicate determinations of molybdenum. __. 31 

Determinations of molybdenum in hidden

splits. _.___-____--__---___--_----.-_ 31

Determinations of molybdenum in check samples. _ ____________-_______-_-__----__-_ 31

Determinations of uranium by different chemists, one laboratory_____________________ 33

Determinations of uranium in hidden splits.-. 33 

Determinations of uranium in the check samples. _______-------_---_----_--------_- 33

Factors for calculating percent of carbon 

dioxide and percent of carbon for various 

sample weights from the volume of carbon 

dioxide under standard conditions.----..__ 36

Determinations of carbonate carbon by different methods and laboratories__________ 36

Determinations of carbonate carbon in hidden

splits _________________________________ 36

Determinations of carbonate carbon in check

samples. _____________________________ 37

Replicate determinations of total carbon. _ _ _ 38 

Determinations of total carbon in hidden

splits. ________________________________ 38

Determinations of total carbon in check and

other samples-_________________________ 38

Replicate determinations of organic carbon _ _ 39 

Determinations of organic carbon in hidden

splits ________________________________ 39

Determinations of organic carbon in check

samples. _____________--__----__-_-_-_- 39

Replicate determinations of organic matter _ _ 40 

Determinations of organic matter in hidden

splits. _____-___---__------------_--_-- 40

Determinations of organic matter in check

samples,_________-__--_-___---_-______ 41

Mean element content and standard deviations of 10 check samples..-__-____-___-_ 41

Summary of the precision and reliability of the

determinations for various elements- - _ _ _ . 42
ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALE

CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE

By L. F. RADER and F. S. GRIMALDI

ABSTRACT

A study of the analytical precision of chemical methods for 

determination of selected minor elements in the Pierre shale is 

reported. The detailed procedures for the determination of 

titanium, vanadium, chromium, manganese, cobalt, nickel, 

copper, zinc, lead, arsenic, selenium, molybdenum, tungsten, 

uranium, carbonate carbon, total carbon, and organic matter 

are described. Alternative methods are also given for the 

determination of titanium, vanadium, nickel, copper, arsenic, 

molybdenum, and tungsten.

The precision of the analytical methods is established from 

replicate determinations made on different days by one chemist, 

replicate determinations by one chemist on paired hidden splits, 

and cross-check determinations on 10 selected samples by different chemists, laboratories, and methods. Graphic comparisons 

are made of determinations by different chemists to indicate 

either the agreement or the bias of results.

INTRODUCTION 

GENERAL REMARKS

Geochemical investigations of the Pierre shale of 

Late Cretaceous age in the western interior part of 

the United States were begun in 1956. The purpose 

of the investigations was to correlate chemical data 

from a large body of typical marine shale and associated sedimentary rocks with their mineralogical compositions, physical characteristics, and geographic and 

stratigraphic variations. These data are important to 

the understanding of the composition of shale, the most 

abundant sedimentary rock, and to the interpretation 

of the geochemical and physical processes by which 

shale is formed. The data will also provide a basis 

for answers to such questions as the possibility that 

ore deposits are formed during the metarnorphism of 

such rocks.

Utilization of laboratories of the U.S. Geological 

Survey was desirable because of the specialized services 

that they offer. The large volume and wide range of 

analytical work anticipated for the study of the Pierre 

shale, however, dictated distribution of analytical work 

to all the laboratories according to their specialties as 

well as to their limitations with regard to prior requests 

for analyses from other projects. As the shale study

was planned to continue for several years, it was 

imperative that the analytical work be uniform and 

comparable in reliability and precision over the full 

period of the study not only with reference to the 

analyses made by each laboratory but also with reference to the analyses made by different laboratories. 

Because data on the performance of specific analytical 

methods were not available, particularly with regard 

to interlaboratory determinations, the analytical work 

was planned to obtain the required information on the 

precision of the methods under actual operating conditions in the laboratories. This plan included selection 

of methods mutually satisfactory to all participating 

laboratories. Accordingly the analytical methods 

agreed upon were prepared in mimeographed form, 

distributed to the analysts, and tested before the shale 

study started.

A total of 70 field samples of Pierre shale and related 

sedimentary rocks used in this study were collected by 

Harry A. Tourtelot, J. R. Gill, and L. G. Schultz. 

After these samples were partially dried and crushed, 

seven of the field samples were each divided into two 

portions and one sample was divided into four separate 

portions by Tourtelot and Gill without the chemists 

being informed of the operation. Each of the 10 new 

samples thus obtained were assigned new and different 

field numbers, ficticious field locations, and different 

serial numbers. This addition to the original 70 

samples made a total of 80 samples. The disguised 

samples are referred to hereafter as the hidden splits.

The objectives of the analytical studies were to 

obtain information on the precision of the determinations for each element in three ways: (a) analysis of 

the 80 samples by the chemist for each specified element, 

with replicate determinations on eight or more samples 

to be made on each sample separately and at a different 

time; (b) the same determinations made by the same 

chemist on the disguised hidden splits included in the 

set of 80 samples; (c) the analyses made by the first 

laboratory checked by a different chemist in a different 

laboratory by analyzing 10 of the 80 samples selected

A-l
A-2 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALE)

by Tourtelot as representative of the shale with regard 

to metal concentration and type of material. The same 

10 samples were used throughout the study as check 

samples for each of 15 different elements namely, 

carbon, titanium, vanadium, chromium, manganese, 

cobalt, nickel, copper, zinc, lead, arsenic, selenium, 

molybdenum, tungsten, and uranium, and are hereafter referred to as the check samples.

In addition, information also was sought on the 

reliability of the determinations in three ways: (a) 

analysis of the 10 check samples by another laboratory 

using a different method where feasible; (b) inclusion 

of quantitative spectrographic analyses for titanium, 

manganese, cobalt, and nickel on the 10 check samples; 

(c) analysis of standard analyzed samples or "certified" 

standard samples.

However, it was impossible and impractical to do 

all that had been planned in conference. Alternative 

methods were supplied for the determination of titanium, vanadium, nickel, copper, arsenic, molybdenum, 

and tungsten but not for the other elements. Thus 

the same methods for some elements were used both 

for the original and check analyses. Regardless of 

how the analyses were made each analyst always 

included reagent blanks and standard solutions with 

each set of determinations. Suitable standard analyzed 

samples were largely unavailable, except for determinations of titanium, chromium, tungsten, and uranium.

Detailed descriptions of all analytical methods 

prepared not only for this study but also for future 

analyses planned for the shale program over the next 

5 years are included in this report. The data on the 

precision and reliability of the methods based on the 

analyses reported in this study are believed to be of 

general interest not only to the chemists involved 

directly, but also to many geologists and others engaged 

in similar work.

LABORATORIES

The laboratories of the U.S. Geological Survey that 

participated in this study are identified for convenience 

in the tables and discussions by the letters A to G, 

as shown below. Corresponding analyses of the 

laboratories are also identified by the letters A to G; 

additional analyses by a given laboratory are designated 

by inferior numbers after the appropriate letter, such 

as A!, A2 , Bj, and B2 .

Laboratory A, Analytical services and research, Denver, 

Colo.

B, Analytical services and research, Washington, D.C.

C, General rock analysis^ Denver, Colo.

D, Rapid rock analysis, Washington, D.C.

Laboratory E, Rock and mineral analysis, Washington, D.C.

F, Spectrographic services and research, 

Denver, Colo.

G, Spectrographic services and research, 

Washington, D.C.

ACKNOWLEDGMENTS

The authors gratefully acknowledge the aid of many 

coworkers. The study was arranged by Harry A. 

Tourtelot and J. J. Tregoning. The collection of 

samples, selection of the hidden splits, and selection 

of the cross-check samples were made by Tourtelot, 

James R. Gill, and Leonard G. Schultz. Earl Dingle, 

Algot Erickson, and William Weston aided in the 

preparation and distribution of the samples.

DIVISION OF WORK

The minor elements in the 80 shale samples were 

determined in laboratories A and B. The distribution 

of the analytical work, by mutual agreement, was for 

A to determine mineral, total, and organic carbon, 

vanadium, manganese, nickel, arsenic, selenium, molybdenum, and tungsten. Laboratory B determined 

titanium, chromium, cobalt, copper, zinc, lead, and 

uranium. The 10 check samples were analyzed in 

laboratory A for those elements originally determined 

in laboratory B and vice versa, except that total and 

organic carbon were determined only in laboratory A 

and tungsten finally was not determined on all the 

shale because analysis of the first 48 samples by laboratory A showed the concentration to be less than 2 ppm 

(parts per million).

A standard rock analysis was made in laboratory C 

on only 25 of the 80 samples of shale, with the additional 

55 samples being anaylzed in laboratory D by rapid 

methods of analysis (Shapiro and Brannock, 1956). 

The work of laboratories C and D made possible the 

cross checking of all 80 determinations made in laboratory A for mineral carbon and manganese and the 

determinations made hi laboratory B for titanium, 

because these three elements are included in both a 

standard and rapid analysis of rocks.

Quantitative spectrographic analyses of the 80 samples, chiefly for elements not determined by chemical 

methods, were made in laboratory F. Only the 

spectrographic data obtained for titanium, cobalt, and 

manganese on the 10 check samples analyzed by 

laboratory F and for titanium and cobalt determined 

by laboratory G are given in this report as the full data 

are reported elsewhere.

Organic matter was determined in laboratory E and 

the check work was done in laboratory A.
CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-3

METHODS SELECTED AND TREATMENT OF DATA

The analytical methods described in this report and 

used for determination of selected minor elements in 

the shale are, to a large extent, adaptations of wellknown procedures taken from the literature, with 

acknowledgment of the source in the literature citations. 

In general, specific instructions for applying a method 

to the determination of an element, if different from 

those reported in the literature, are the result of 

critical study and testing by either laboratory A or B 

while adapting the method to routine use. The 

methods described are suitable for the analysis of shale 

or silicate rock but are not intended for general application to other types of material without further 

investigation. The lower threshold limit of the methods was arbitrarily set at 1 ppm. In general, this limit 

meets the needs of most geologic or geochemical 

studies.

Methods are described for the determinations of 

titanium, vanadium, chromium, manganese, cobalt, 

nickel, copper, zinc, lead, arsenic, selenium, molybdenum, tungsten, uranium, carbonate carbon, total 

carbon, and organic matter. Alternative methods 

are given also for the determinations of titanium, 

vanadium, copper, nickel, arsenic, molybdenum, and 

tungsten. The arrangement of the methods is generally 

based on the atomic number of the element. Methods 

for copper, zinc, and lead are grouped together because 

of the common separation and determination with 

dithizone. Methods for carbon and organic matter 

are placed last.

Analytical data obtained in this study and upon 

which the precision and reliability of the methods are 

estimated are tabulated with the individual methods for 

each element. In general, the complete data for each 

element on all 80 of the samples are not included in this 

report, because they will be reported and discussed in 

another part of the study of the Pierre shale by H. A. 

Tourtelot and others. However, complete data are 

presented for mineral carbon, titanium, manganese, and 

uranium, because these four elements were determined 

on all 80 samples by two or more analysts or laboratories. The data for the other elements on only part of 

the samples are arranged to compare the replicate determinations by one analyst, the results of one analyst 

on the paired hidden splits, and the results of all analysts and laboratories on the check samples. Replicate 

determinations by one chemist are ranked according to 

concentration of the element in the samples, without 

regard to serial number, in order to facilitate study of 

the data. This arrangement was not used, however, 

for either the hidden splits or check samples because

identification by sample number, in a systematic 

arrangement, is advantageous for cross comparisons 

between tables and elements on these selected special 

samples.

The data on the 10 cross-check samples are plotted 

to show the bias or the agreement between analysts 

and (or) methods. The data on the check samples 

obtained by the chemist in laboratory A or B when the 

analyses of the 80 samples were made are arbitrarily 

plotted as the ordinate. Data from other-chemists or 

methods are plotted as the abscissa. The points 

representing each determination on the graph show 

the deviation of the results from the theoretical line 

connoting perfect agreement. It is neither assumed 

nor implied that the results of the chemist analyzing 

the 80 samples for a particular element are either more 

precise or more accurate than those of another analyst. 

Also, the consistent use of such data as the ordinate 

makes possible a systematic plot of original data to 

cross-check data.

Many of the analytical results reported in the tables 

are in good agreement and require but little study to 

determine the deviations between methods and analysts. Nevertheless the standard deviations of the 

determinations have been calculated in order to obtain 

a comparative evaluation for the work by different 

chemists, methods, and laboratories. The data for 

some elements are insufficient to give good estimates of 

the standard deviations and, therefore, such values 

must be used with caution. The calculation of the 

standard deviation for several definite concentration 

ranges was attempted but was only partly successful 

because of too few samples in each range for certain 

elements. The ranges of concentration arbitrarily 

selected are from 0.00005 to 0.0005 percent, 0.0005 to 

0.005 percent, 0.005 to 0.05 percent, 0.05 to 0.5 percent, 

0.5 to 5 percent, and 5 to 50 percent. The selection 

of 5, or the midpoint of a decimal unit, as the range 

limits, enables one to compare chemical with semiquantitative spectrographic data that are reported in a 

similar manner.

The calculation of the standard deviation was made 

using pairs of analytical determinations as described 

by Youden (1951, p. 16). The data for the 10 check 

samples are arranged to show the mean value for determinations on each sample as well as the maximum 

difference between determinations. These differences 

make possible the rapid calculation of an approximate 

standard deviation from limited data ranging from 2 

to 10 determinations, as described by Dixon and Massey 

(1951, p. 239). Other statistical treatment of the data 

was not undertaken.
A-4 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALEi

SAMPLE PREPARATION

The field samples, collected in 1957 by Harry A. 

Tourtelot, James R. Gill, and Leonard G. Schultz, 

were prepared for analysis by laboratory A, because 

control of the variables of grinding, mixing, and splitting to one controlled operation was desirable. The 

preliminary work of preparing the analytical splits, 

however, was done by Tourtelot and Gill. They removed the fine extraneous material from each field 

sample by emptying the sample sacks, one at a time, 

on a plastic-coated grating (about two holes per inch) 

and lifting the larger discrete pieces of shale away 

from the fine material by raising the grating. The 

large chunks of shale from the grating were resacked, 

assigned a serial number, and the sacks of shale 

placed in an electrically heated drying oven maintained at 93 °C. The samples were dried under 

these conditions for about 48 hours to a moisture 

level ranging from about 2 to 10 percent in order 

to enable use of motor-driven crushing and grinding equipment. The' partially dried samples were 

crushed to about 8-mesh size or finer by passing them, 

one at a time, through a motor-driven jaw crusher, and 

each crushed sample was resacked. The hidden splits 

were then prepared by Tourtelot and Gill as previously 

mentioned, and the 80 samples, including 65 samples 

of shale, 10 of bentonite, and 5 of marl were then ground 

to a finer size as described below.

The standard procedure and equipment used for 

sample preparation are those described by Huleatt 

(1950), except that the samples of shale were ground 

with alumina-ceramic plates mounted on a motordriven sample pulverizer in order to avoid contamination from the alloying elements of steel plates (Barnett 

and others, 1955). As other details of sample preparation also differ somewhat from normal practice 

because of sample size (2 to 100 Ib) and number of splits 

required, the procedure used is described briefly.

The crushed partially dried material was mixed for 

4 hours, one sample at a time, in a power-driven rotating drum containing mixing baffles. Each sample was 

then split into four equal portions by use of a Jones 

splitter. One of these portions was further split until 

1 pound of each sample was isolated as the portion for 

analytical work. These 1-pound samples were ground 

to approximately 80- to 100-mesh size, usually by one 

pass through the motor driven alumina-ceramic plates, 

except for nine samples that were ground on a special 

hammer mill (Ross and Hardesty, 1942). These nine 

samples could not be ground to the desired fineness on 

the alumina-ceramic plates, mostly because of differences in moisture content or in physical characteristics. Each sample was remixed for about 4 hours and 

split once more into four portions of about 4 ounces

each, which were then bottled, labeled, and distributed 

to laboratories A, B, and C.

Laboratory C further processed its splits for use in 

standard and rapid rock analysis. The samples were 

spread out on clean paper for about 20 hours to reach 

equilibrium under moisture conditions existing in the 

laboratory. Each sample was then screened through 

80-mesh bolting cloth. The part, if any, not passing 

through the 80-mesh cloth was reground in an agate 

mortar and mixed back into the sample by rolling 

it on a mixing cloth. Only about six samples failed to 

pass through the 80-mesh cloth completely when sieved 

and the part of these coarser than 80 mesh amounted 

to not more than 2 grams. One 35-gram portion of 

each sieved sample was split for distribution either to 

laboratory C or D. Of the 80 samples, 25 were for 

standard analysis and the remaining 55 for rapid analysis for the major oxides. In addition one 7-gram portion of each sieved sample was reserved for spectrographic analysis by laboratory F These small splits 

were further ground by an additional pass through the 

alumina-ceramic plates at the request of the spectrographers who desired a more finely ground material. 

Laboratory G was not supplied with sample splits at 

this time but later analyzed the 10 check samples, by 

obtaining 4 of them from laboratory F and the other 6 

samples from laboratory D.

METHODS FOR THE DETERMINATION OF INDIVIDUAL 

CONSTITUENTS

TITANIUM

PEROXIDE METHOD

[Range in shale: 0.05 to 0.5 percent titanium] 

PRINCIPLES

Titanium in acid solution reacts with hydrogen 

peroxide to give a yellow color whose intensity is proportional to the amount of titanium present (Weller, 

1882). Several other elements, particularly vanadium, 

react in the same manner. The ratio of titanium to 

vanadium in shale is sufficiently high so that no provision is made to separate titanium from vanadium. 

The error introduced is small because the absorbance of 

the vanadium peroxide complex for a given weight of 

vanadium is only about one-third that given by an equal 

weight of titanium when measurements are made at 400 

m/i (millimicron).

Titanium can be separated from vanadium, when 

desirable, by precipitation of the titanium from the 

solution of the sample with sodium hydroxide. A 

small amount of ferric iron is added as a carrier when the 

sample contains negligible amounts of iron.

In the spectrophotometric determination, phosphoric 

acid is added to bleach the color of ferric iron. It is 

important that the same amount of phosphoric acid and
CHEMICAL ANALYSES FOE SELECTED MINOR ELEMENTS IN PIEEEE SHALE A-5

alkali sulfate be added to both samples and standards, 

as these reagents tend to bleach the peroxytitanium 

slightly. Fluoride must be completely absent.

The results obtained are corrected for the absorbance 

of a small amount of platinum dissolved during the 

pyrosulfate fusion. Ordinarily the correction corresponds to no more than 0.02 percent titanium for the 

size of sample recommended.

APPARATUS AND REAGENTS

Beckman DU spectrophotometer.

Hydrogen peroxide, 3 percent: Dilute 10 ml of 30 percent hydrogen peroxide to 100 ml with pure water. This solution tends 

to deteriorate on standing and should be made fresh when 

needed.

Standard titanium solution, 1 ml = 0.4 mg Ti: Dry a portion of 

National Bureau of Standards standard sample 154 (98.7 

percent TiO2) at 105°C. Transfer 0.1690 g to a Vicor or 

silica crucible, blend thoroughly with 3 g potassium pyrosulfate, cover the crucible, and heat until the sample is completely 

fused. Cool the crucible, place crucible and contents in a 

beaker containing 50 ml 1 +1 sulfuric acid, and digest the solution on a steam bath until the melt is completely dissolved. 

Cool the solution and dilute to 250 ml in a volumetric flask. 

An alternative procedure recommended on the certificate of 

standard sample 154 is given under the reagent section of the 

alternative tiron method for determination of titanium.

Standard titanium, dilute solution, 1 ml=20 micrograms Ti: 

Dilute 10 ml of the standard stock solution, prepared as 

directed, to 200 ml with water. Prepare this diluted solution 

fresh as needed.

Potassium pyrosulfate: Dissolve 28 g in 10 percent v/v sulf uric 

acid and dilute to 200 ml with 10 percent v/v sulfuric acid.

PROCEDURE

1. Weigh a 0.5-g sample into a 50-75-ml platinum dish. Remove organic matter by igniting gently at first and raising 

the temperature finally to about 700°C. Cool.

2. Moisten the sample with water. Add to the dish 10 ml 

hydrofluoric acid, 5 ml nitric acid, 2 ml 1 + 1 sulfuric acid. 

Cover the dish with a platinum cover and digest on the 

steam bath for 30 minutes. Remove the cover and evaporate the solution on the steam bath to remove water. 

Heat the solution to fumes of sulfuric acid. Cool. Carefully add 15 ml water to the dish and again evaporate to 

fumes of sulfuric acid. Cool.

3. Add 2.25 g of potassium sulfate to the dish and let stand a few 

minutes to allow the sulfate to be converted to potassium 

acid sulfate (the amount of K2SC>4 specified will react with 

about 1.35 ml of 1 + 1 HjSCU). Heat the solution very 

gently on a hot plate at 200°C. to remove water and any 

free sulfuric acid not fixed as potassium pyrosulfate. Continue heating until a clear pyrosulfate melt is obtained and 

then for a few minutes longer to ensure that all fluoride is 

removed (fluoride seriously interferes by bleaching the peroxytitanium). Cool the melt. Add 20 ml of 10 percent 

v/v sulfuric acid to the dish and warm the solution to 

dissolve the salts.

4. Transfer the solution to a 25-ml volumetric flask using 10 

percent sulfuric acid for the transfer and to adjust the 

volume to 25 ml.

5. Transfer 10 ml to a 50-ml volumetric flask. Add 2 ml 1 + 1 

phosphoric acid, 3 ml of 3 percent hydrogen peroxide, and 

dilute to mark with 10 percent v/v sulfuric acid. Deter692016 0 61 2

mine the absorbance of the solution against water at 400 m^. 

A reagent-blank correction must be determined. This is 

conveniently done by analyzing several weighed portions 

of Portland cement, National Bureau of Standards standard 

sample 177. The difference between the certificate value 

for titanium and the average of the results obtained is 

taken as the blank correction for the unknown samples. 

6. Calculate the percentage of titanium in the sample.

STANDARD CURVE

Transfer aliquots of standard titanium solution containing 0, 0.5, 1, and 2 mg of titanium to 50-ml volumetric flasks. Add 10 ml of potassium pyrosulfate 

solution to each flask. Although 10 ml of potassium 

pyrosulfate is specified, the amount required depends 

on the size of aliquot taken at step 5 for the sample. 

For every 1 ml of sample, 1 ml of pyrosulfate solution 

is used for the standards. Dilute the solution with 

10 percent v/v sulfuric acid to 25-ml volume. Add 

2 ml of 1 + 1 phosphoric acid and 3 ml of 3 percent 

hydrogen peroxide. Dilute to volume with 10 percent 

v/v sulfuric acid. Determine absorbance at 400 m/i 

against water as a reference.

ALTERNATIVE TIRON METHOD

[Range in shale: 0.05 to 0.5 percent titanium] 

PRINCIPLES

Tiron (disodium-l,2-dihydroxybenzene-3, 5-disulfonate) forms yellow complexes with titanium, molybdenum, uranium, and osmium and purple complexes with vanadium and iron over the pH range 4.3 to 9.6. Yoe and, 

Armstrong (1947) used tiron for the determination of 

titanium in siliceous materials. This method is an 

extension of the procedures of Yoe and Armstrong 

and of Shapiro and Brannock (1956, p. 36-37) to the 

determination of titanium in shale and related rocks. 

Iron interference is overcome by reducing iron to the 

ferrous state with sodium dithionite in a buffered 

solution at pH 4.7. The concentrations of vanadium, 

molybdenum, osmium, and uranium in the shale are 

too small to interfere significantly when the absorbance 

of the titanium complex is determined at 430 m/i. The 

titanium-tiron color complex follows Beer's law to as 

much as 150 micrograms titanium in a 50-ml volume 

when the absorbance of the solution is determined 

immediately after the iron is reduced.

REAGENTS

Tiron solution: 1.0 g tiron dissolved in 50 ml of water. This 

solution should be made up immediately before use.

Buffer solution: 40 g of ammonium acetate and 15 ml glacial 

acetic acid diluted to 1 liter with distilled water.

Sodium dithionite (sodium hydrosulphite): Dry powder.

Titanium standard solution, 1 ml=0.5 mg Ti. Method of 

Plechner and Jarmus (1934) is given on the certificate received 

with National Bureau of Standards standard sample 154: 

Weigh and transfer to a 250-ml beaker 0.4225 g standard
A-6 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALEi

sample 154 (98.7 percent titanium dioxide) that has been 

dried at 105°C. Add 10 g of ammonium sulfate and 25 ml 

of sulfuric acid to the beaker and heat the solution cautiously 

over flame to incipient boiling. Continue to heat the solution 

until all the titanium is dissolved. Cool the solution and 

rapidly pour it into 450 ml of cool water while stirring the 

water. Rinse the beaker with 5 percent v/v sulfuric acid, 

mix, and set aside overnight. Filter the solution through a 

glass-fritted crucible and dilute to 500 ml in a volumetric flask. 

Standard sample 154 contains 0.7 percent SiO2 and 0.6 percent 

of other metals that are largely filtered from the solution of 

titanium by following this method of solution. Other samples of 

reagent grade TiO2 probably are contaminated with certain 

impurities also, and if used for preparing a standard may require 

standardization of the solution as described, for example, 

by Hillebrand and others (1953, p. 582-583).

PROCEDURE

1. Weigh and transfer 0.5 g of sample to a 75-ml platinum 

crucible.

2. Remove organic matter by igniting gently at first and gradually raising the temperature to 700°C in a muffle furnace. 

Cool.

3. Moisten the sample with water. Add 3 ml of nitric acid, 

5 ml sulfuric acid, and 10 ml of hydrofluoric acid.

4. Cover the crucible and digest the solution overnight on a 

steam bath.

5. Remove the cover. Evaporate the water and heat the 

solution on a hot plate until copious fumes of sulfuric acid 

form. Stop fuming the solution when about 4 ml of 

sulfuric acid remains.

6. Add 50 ml distilled water to the crucible, cover, and digest 

on steam bath to dissolve the salts.

7. Transfer the solution to a 250-ml volumetric flask, cool, and 

dilute to volume.

8. Transfer a 5-ml aliquot to a 100-ml beaker. A blank and 

standard also are started in two additional beakers. Add 

5 ml of water to the first beaker for the blank and 5 ml of 

standard dilute titanium solution to the second beaker for 

the standard.

9. Add 10 ml of tiron solution to each beaker and adjust the pH 

to about 4.7 with dilute ammonium hydroxide. Then 

buffer the solutions by adding 50 ml buffer solution to each 

beaker and mix.

10. Add 10 to 20 mg sodium dithionite powder to the blank. 

Mix gently by rotating the beaker two or three times. 

After 1 minute, pour the blank solution into a 2-cm absorption cell and adjust the spectrophotometer to read zero 

absorbance at 430 m^.

11. Repeat step 10 with each solution in turn, adding dithionite, 

waiting about 1 minute, and reading absorbance against 

the blank solution as a reference.

12. Calculate the percentage of titanium in the sample.

STANDARD CURVE

A standard curve generally is not constructed because 

the absorbance of the blank, standard, and unknown 

are determined separately for each sample solution. 

However, such a plot of previous data can be useful as 

a reference when the method is used at infrequent 

intervals.

PRECISION OF TITANIUM DETERMINATIONS

Titanium was determined on the 80 samples in laboratory B with the peroxide method as described. The 

range 0.05 to 0.5 percent titanium applied to all 80 

samples. No duplicate determinations were reported 

by B and so the precision of determinations by one 

chemist cannot be calculated. A standard sample, 

National Bureau of Standards standard sample 177 

(Portland cement), with a certificate value of 0.16 

percent titanium, was analyzed three times for titanium 

in laboratory B while the titanium in the shale samples 

was being determined. Results of 0.15, 0.15, and 0.15 

percent titanium were obtained.

0.50 0.50r

TITANIUM, IN PERCENT 

LABORATORY A

TITANIUM, IN PERCENT 

LABORATORY C + D

0.50

0.50 0.50

TITANIUM, IN PERCENT 

LABORATORY F

TITANIUM, IN PERCENT 0' 50 

LABORATORY G

FIGURE l. Comparison of titanium determinations of B with those of A., C+D, F,

andO.

Laboratories C and D jointly reported TiO2 on all 

80 samples of shale. These determinations, calculated 

to titanium, are compared with those of B in tables 1, 

2, and 3. Table 1 gives the results, and standard 

deviations calculated from paired data for all samples 

except the hidden splits and the check samples. Table

2 gives similar data by laboratories B, C, and D on the 

hidden splits. The results on the check samples by 

laboratories A, B, C, D, F, and G are reported in table

3 together with the standard deviations calculated 

from paired data and from the maximum to minimum 

difference.

Figure 1 graphically compares the data of A, C+D. 

F, and G on the check samples with those of B.
CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-7

TABLE 1. Determinations l of titanium, in percent, by different 

laboratories

[Add 259500 to each sample number to form serial number]

Sample

42 . 

57- _ .. 

41 ..

56

58 

77 

78 

75 ..

59 ...

47 

43 ......

26- _ ....

79 ..

81--. _ ..

B

0.15 

.23

.25

.31

.35

.36 

.36 

.37

.38

.39

.41

.46

.48

.48

C

0.13

.25 

.04

.30

.33

.34 

.33 

.35

.37

.37

.37

.44

.46

.47

Sample

38... 

60 

36 

44 

29. 

67 

38 

83 

51 

40 

£0 

62 

55 .. ....

72 

93 . 

91 

45 

54 

52 

64 

B

0.14 

.21 

.23

.23

.25

.25 

.26 

.26

.28

.30

.31

V)

.33

.34

.34

.35

.36

.36

.37

.37

D

0.10 

.22 

.23

.21

.25

.25 

.25

97

90

.29

.31

S9

*>K

.35

.34

.33

.35

.38

.36

.36

Sample

89 

35 

61 

95 

7*>

34 

66. 

76 

30

70 

84

27 

*>0

87 

fid

71 

31 ........

85 

74 

on

B

0.37 

.38 

.38

.38

.39

.40 

.40 

40

.42

.42

.42

43

.43

.43

.44

.44

.45

.47

.49

.58

D

0.36 

.36

.41

.37

.40

.38 

.40 

.40

.39

.42

.42

.41

.44

.46

.43

.42

.47

.44

.44

'Precision and reliability of determinations in the range 0.05 to 0.5:

B, C ...........................

B, D. . .............

>One low result (sample 41) rejected.

Standard Number of

deviation comparisons

10.015 14

.020 40

B. Peroxide method of this report; Charles Kinser, analyst.

C. Standard rock analysis, peroxide method; Marguerite Seerveld and Vertie Smith,

analysts. 

D. Tiron method (Shapiro and Brannock, 1956); Leonard Shapiro, Paul Eimore,

Samuel Botts and Marvin Mack, analysts.

TABLE 2. Determinations l of titanium, in percent, in hidden 

splits by three laboratories

[Add 259500 to all sample numbers, except 03 and 04 to which add 259600, to form serial 

numbers. Groups indicate the samples that were duplicates]

Sample

33 

97 

49. .. __

96 .

99 . _ ...

03 

53- .... .......

04 

65. .

98.- __ ...

B

0.21 

.21

.35

.37

.36

.36

.22

.23

.41

.42

C

0.20 

.28

.38

.22

4fi

D

"6!" 26"

.30

.30

.23

.41

Sample

68. _ .

01 

80

00 

82 

02 

86 

05 

B

0.42 

.44

.42

.43

.33

.38

.44

.46

C

0.41 

40

.34

.43

D

~~o~la

.41

.37

.43

i Precision and reliability of determinations in the range 0.05 to 0.5:

Standard Number of 

deviation comparisons 

....................................... 0.013 13

 ..._.__ .. 0.030 18

B. Peroxide method of this report; Charles Kinser, analyst.

C. Standard rock analysis, peroxide method; Marguerite Seerveld and Vertie Smith,

B.. . 

B, C+D.

D. Tiron method (Shapiro and Brannock, 1956); Leonard Shapiro, Paul Eimore, 

Samuel Botts, and Marvin Mack, analysts.

TABLE 3. Determinations l of titanium, in percent, in check

samples

[Add 259500 to each sample number to form serial number]

Sample

28 . 

33- - 

37---- 

39 - 

46-.- - 

48...- 

49--- 

63 

92 

94- 

B

0.13

.21

.16 

.27

.41 

.15 

.35

.42

.42 

.44

A

0.14

.19

.17 

.25

.40 

.15 

.27 

.43

.39 

.39

D

0.13

.14 

.26

.40

.41

.44

C

0.20

~~.~14~ 

.28 

.43

G

0.16

.18

.14 

.22

.32 

.12 

.22

.46

.40 

.40

Jr

0.20

.20

.15 

.23

.35 

.13 

.23

.47

.43 

.43

Mean

0.15

.20

.15 

.25

.38

.14 

.27 

.44

.41 

.42

Difference 

(max min)

0.07

.03

.03 

.05

.09 

.03 

.13 

.05

.04

.05

Standard 

deviation

0.030

.013

.013 

.022

.039 

.013 

.056 

.022

.017 

.022

Precision and reliability of determinations in the range 0.05 to 0.5:

B, A 

B, C 

B, D- -

B, F 

B, G-__ 

Avg spectrographic, avg chemicalAll data, 

Standard Number of

deviation comparisons

0.024 10

.025 4

.008 6

. 051 10

. 058 10

.029 10

. 026 100

B Peroxide method of this report; Charles Kinser, analyst.

A Alternative tiron method of this report; Claude Huffman, analyst.

D Tiron method (Shapiro and Brannocx, 1956); Leonard Shapiro, Paul Eimore,

Samuel Botts, and Marvin Mack, analysts. 

C. Standard rock analysis, peroxide method; Marguerite Seerveld and Vertie Smith,

analysts.

G. Spe3tro?raphic analysis; Harry Rose, analyst. 

F. Spectrographic analysis; Paul Barnett, analyst.

VANADIUM

FUSION-LEACH SEPARATION METHOD

[Range in shale: 0.001 to 0.5 percent vanadium] 

PRINCIPLES

The sample is fused with a mixture of sodium carbonate and magnesium oxide. The alkaline melt is 

leached with water. Most of the silica is retained in 

the insoluble residue. Vanadium in the nitrate is 

determined spectrophotometrically as the phosphotungstovanadic acid (Sandell, 1950, p. 607-609). An 

aliquot of the original sample solution is used hi the 

reference cell to compensate | for small amounts of 

chromate, if some should remaija.

Tests show that 10 parts of chromate are equivalent 

to 1 part vanadium under the conditions of the method. 

If a reagent blank is used as the reference solution, the 

results will be high to the extent of one-tenth of the 

chromate in the solution; however, the chromium content of the Pierre shale is ordinarily too small to interfere significantly.
A-8 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALE

APPARATUS AND REAGENTS

Beckman DU spectrophotometer with 1- and 5-cm cells. 

Fusion mixture: Prepare an intimate mixture of four parts

sodium carbonate to one part magnesium oxide by weight. 

Sodium tungstate: Dissolve 20.6 g sodium tungstate dihydrate

in water and dilute to 100 ml. 

Standard vanadium stock solution, 1 ml=l mg V: Dissolve

0.4592 g of ammonium metavanadate (NH^VOs) in water and

dilute to 200 ml in volumetric flask. 

Standard vanadium, dilute solution, 1 ml =10 micrograms V:

Take 5 ml of stock solution and dilute to 500 ml in a volumetric

flask.

PROCEDURE

1. Mix intimately 1 g sample with 6 g fusion mixture in a 

platinum crucible. Cover with 1 g more of mixture. 

Include a blank with each set of samples.

2. Heat the crucible at 650°C for 30 minutes, gradually raise 

temperature to 900°C and heat for 30 minutes longer or 

until organic matter is destroyed.

3. Leach the melt by gently boiling in a 150-ml beaker with 50 ml 

water containing a few drops of alcohol to destroy manganate. 

Break up all lumps. Let the insoluble material settle and 

filter the solution into a 250-ml beaker, washing with 

hot 0.1 percent sodium carbonate solution. Cool.

4. Carefully (otherwise CO2 evolution may cause spillage of 

sample) add 1+1 nitric acid by graduated pipet until 

phenolphthalein is colorless, then add an equal volume of 

acid to convert sodium bicarbonate to carbon dioxide and 

sodium nitrate. Add 6 ml 1+1 nitric acid in excess. 

Place the beaker on a steam bath and evaporate the solution 

to about 50 ml. Transfer the solution to a 100-ml volumetric flask, cool, and dilute to volume with water.

5. Transfer a 20-ml aliquot to eash of two 25-ml volumetric flasks. 

Add 2.5 ml of 1 + 2 phosphoric acid to each flask. Add 

1 ml sodium tungstate solution to one flask but not to the 

other flask. Warm the flasks on a steam bath for 15 minutes, 

cool, and make to volume.

6. Determine the absorbance of the solutions in 5-cm cells at 

400 m/t using the solution containing no tungstate as the 

reference.

7. Calculate the percentage of vanadium in the samples.

STANDARD CURVE

Take two sets of 0, 10, 30, 50, and 100 micrograms 

of standard vanadium solution in 25-ml volumetric 

flasks. Add 1.2 ml 1 + 1 nitric acid to each and enough 

water to make 18 ml. Add 2.5 ml of 1+2 phosphoric 

acid and 1.0 ml sodium tungstate solution to one set 

but only add 2.5 ml of 1+2 phosphoric acid to the 

second set of flasks. Warm the solutions on a steam 

bath for 15 minutes, cool, and dilute to volume. 

Determine the absorbance of the first set of solutions 

(containing added tungstate) against corresponding 

members of the second set (without added tungstate) 

at 400 mju. Plot the absorbance differences against 

the vanadium concentrations.

Alternatively weigh five portions of flux, transfer to 

150-ml beakers (omit fusion), and carry through the 

procedure beginning at step 3. Add standard vanadium solution to four of the five blank solutions 

at steps 3 or 5, as preferred, and complete the determinations as described.

ALTERNATIVE CUPFERRON SEPARATION METHOD

[Range In shale: 0.0001 to 0.025 percent vanadium] 

PRINCIPLES

Although the first procedure for the determination of 

vanadium can be extended somewhat to determine 

smaller amounts of vanadium than indicated, the following procedure is more suitable for the determination 

of vanadium in concentrations below 0.01 percent in 

shale. A larger sample is used and vanadium is 

separated by precipitation with cupferron, iron from the 

sample acting as a carrier. The precipitate is ignited, 

transferred to a silver crucible, fused with sodium 

hydroxide, leached with water, and filtered to separate 

iron. Vanadium in the filtrate is again determined as 

the phosphotungstovanadic acid.

Attempts to use sodium carbonate in place of sodium 

hydroxide in the fusion of the ignited cupferron precipitate resulted generally in incomplete recovery of 

vanadium. The magnitude of the error from this 

source is largely determined by the amount of iron 

present and can be as much as 40 percent for samples 

containing 15 percent iron oxide. On the other hand, 

fusion with sodium hydroxide gives better than 96 

percent recovery of the vanadium.

APPARATUS AND REAGENTS

Beckman DU spectrophotometer with 5-cm cells.

Sodium tungstate and standard vanadium solutions: Same as in 

first method.

Cupferron solution, 6 percent w/v aqueous: Prepare only when 

needed and keep it cold.

Ferric nitrate solution, 1 ml contains approximately 5 mg of 

ferric oxide: Dissolve 5.06 g of ferric nitrate 9-hydrate with 

10 ml of 1 +1 nitric acid and water and dilute to 200 ml. Five 

milliliters of this solution is used for the blank so that a precipitate will be obtained in the cupferron precipitation

PROCEDURE

1. Transfer a 2-g sample to a platinum dish and destroy organic 

matter by heating at 500° to 700°C.

2. A blank containing 5 ml of ferric nitrate solution is carried 

along with the samples. Reference is made only to the 

sample. Moisten the sample with water, add 20 ml hydrofluoric acid, 5 ml nitric acid, and 10 ml perchloric acid to the 

dish. Cover the dish and digest the solution 30 minutes 

on a steam bath. Evaporate solution to fumes of perchloric acid. Add 10 ml water and evaporate the solution 

to fumes again. Repeat the addition of water and evaporate the solution to fumes again.

3. Add 20 ml hydrochloric acid and 30 ml water to the dish and 

digest the solution to dissolve soluble salts. A clear solution should be obtained. Transfer the solution to a 500-ml 

Erlenmeyer flask, with enough water to make the volume 

230 ml.
CMEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-9

4. Chill the solution in an ice bath. Add 70 ml of cold 6-percent 

cupferron solution (more if required to precipitate all the 

iron). Stir in paper pulp, and shake the stoppered flask 

vigorously to coagulate the precipitate. Filter the solution 

by suction, using a platinum filter cone and a close-textured 

paper.

5. Wash the precipitate with a cold solution containing 40 ml 

hydrochloric acid and 15 ml of cupferron to 500 ml of solution. Reject the filtrate and washings.

6. Transfer the filter and precipitate to a platinum crucible and 

dry carefully on a hot plate until charred or overnight in an 

oven at 50° C.

7. Ignite the precipitate at a low heat; very gradually raise the 

temperature to 625° C, then maintain this temperature 

until the carbon is removed.

8. Transfer the residue to a silver, crucible and fuse with 3 g 

sodium hydroxide. Alternatively fuse the residue in a 

nickel crucible with 3 g sodium hydroxide containing 1 g 

sodium carbonate. Leach the melt with 20 ml of water by 

boiling in a small beaker on a hot plate.

9. Chill the solution in an ice bath and filter it into a 50-ml 

volumetric flask using a hardened paper. Wash the filter 

with 10 ml of 0.1 percent sodium hydroxide solution. 

Reject residue.

10. Titrate a solution from a blank fusion with concentrated 

nitric acid to the methyl orange end point to determine the 

amount of nitric acid required to neutralize the alkali. Add 

this amount of nitric acid to all samples plus 1.2 ml in excess.

11. Add 5.0 ml of 1 + 2 phosphoric acid and 2.0 ml sodium tungstate solution to each flask. Warm on steam bath 15 minutes, cool, and dilute to volume of 50 ml.

12. Determine the absorbance of the sample solution against a 

blank solution carried through the method. Use 5-cm 

cells and a wave length of 400 m/z.

13. Calculate the percentage of vanadium in the sample.

STANDARD CURVE

Establish a standard curve with aliquots of vanadium 

solution containing 0, 20, 40, 80, 100, and 200 micrograms vanadium in 50-ml flasks. Add 2.4 ml 1 + 1 

nitric acid to each flask and follow the procedure from 

step 11, using the blank solution as reference.

PRECISION OF VANADIUM DETERMINATIONS

Vanadium was determined on the 80 samples of 

shale in laboratory A with the fusion-leach phosphotungstate method described. The ranges of concentration for vanadium were from 0.0005 to 0.005 percent 

(10 samples), 0.005 to 0.05 percent (61 samples), and 

0.05 to 0.5 percent (9 samples). The results and the 

precision are given in tables 4, 5, and 6.

The alternative method (cupferron separation) includes a fusion of the ignited cupferrates to redissolve 

the vanadium completely. Sodium hydroxide or 

sodium hydroxide-sodium carbonate flux is specified 

for this fusion because small amounts of vanadium in 

the presence of large amounts of iron generally are not

made completely soluble by the usual fusion with 

sodium carbonate alone. However, when the Fe2O3 

content of the sample is less than 5 percent, simple 

carbonate fusion of the cupferrates is effective as shown 

in table 7. Here the results obtained are compared 

with those obtained by the fusion-leach method. The 

standard deviation of results by the two methods for 

33 samples (table 7) is 0.0018 percent vanadium. 

When the iron content was greater than 5 percent, 

data not reported here on 47 samples showed a standard 

deviation from the first method of 0.0060 percent vanadium, all with a low bias.

Figure 2 is a plot of vanadium determinations of A 

compared with those of AI, A2 , and B. The scatter on 

the vanadium results was greater than that usually 

obtained on the results of the four hidden splits (table 

5) of one sample containing about 17 percent pyrite, 

as calculated from the sulfur content of the sample.

1000 lOOOr

1000 

VANADIUM, IN PARTS PER MILLION

LABORATORY A,

1000

VANADIUM, IN PARTS PER MILLION 

LABORATORY A2

1000

1000

VANADIUM, IN PARTS PER MILLION 

LABORATORY B

FIGURE 2. Comparison of vanadium determinations of A with those of Ai, Az, and B.

TABLE 4. Replicate determinations l of vanadium, in percent, 

by laboratory A

[Analysis by fusion-leach phosphotungstate method, Wayne Mountjoy and William 

Goss, analysts. Add 259500 to all sample numbers, except 05 to which add 259600, 

to form serial numbers]

67.. -- -

OQ

42... 

9ft

05 

i Precision and 

deviation, 0.0015;

... 0.004 0.004 35.. 

_- .004 .003 33-. 

...... .006 .005 45 

...... .006 .005 52-..-.

... .- .006 .006 92..--.

...... .017 .018

reliability of determinations in 

number of comparisons. 11.

 ..... ... ... 0.018

_ . .020

_ .... .024

- -- .026

-- _- .020

... ... ... .029

0.022 

.019 

.025 

.021 

.023 

.030

the range 0.005 to 0.5: standard
A-10 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALE)

TABLE 5. Determinations l of vanadium, in percent, in hidden 

splits by laboratory A

[Analyses by fusion-leach phosphotungstate method; Wayne Mountjoy and William 

Qoss, analysts. Add 259500 to all sample numbers, except 00 to 05 to which add 

259600, to form serial numbers. Groups indicate the samples that were duplicates]

33

97

49

%

99

AO

1

_ ______. 0.020

....... .......... .018

... _ ... .. .059

................. .075

nfii

Precision and reliability 

0.005-0.05-- .

53.. 

04 

65 

98. 

68 

01 -

of determinations: 

Range

.05- .5 ...... ..... ..............

. 0.021 80

. . 019 00

. . 012 82

. . 013 02

. . 021 86.

. . 022 05.

... - 0.013

. . .011

. - .038

.- .043

........ _ ...... .021

 ... - - .018

Standard Number of 

deviations comparisons 

0. 0019 7 

.0098 6

TABLE 6. Determinations l of vanadium, in percent, in check

samples 

[Add 259500 to each sample number to form serial number]

Sample

28 

33 

37 

so

46. 

48 

49 

63 

92 

94 - 

A

0.007

.020

.002

.020

.023

.058

.074

.034

.023

.021

A,

0.007

.016

<.001

.020

.024

.062

.093

.038

.024

,023

A2

0.008

.024

.003

.023

.025

.062

.079

.039

.024

.024

B

0.007

.020

.001

.021

.021

.062

.075

.037

.022

,021

Mean

0.007

.020

.002

.021

.023

.061

080

.037

.023

.022

Difference (max 

min)

0.001

.008

.003

.003

.004

.004

.019

.005

.002

.003

Standard delation

0.0005

.0039

.0015

.0015

.0019

.0019

.0092

.0024

.0010

.0015

1 Precision and reliability of determinations:

A, Ai._ ___ ..... ... .... ......

A, Aj. .... ... .... -

A, B......... ......................

All data 

Range

0.005 to 0.05

Standard delation

0.0016 

.0019 

.0009 

.0018

Number 

of 

comparisons

8 

8 

8 

48

0.05 to 0.5

Standard deviation

0.0097 

.0032 

.0025 

.0064

Number 

of 

comparisons

2 

2 

2 

12

A. Fusion-leach separation of vanadium; Wayne Mountjoy and William Qoss,

analysts. 

Ai. Cupferron method, NaaCOj-NaOH fusion; Wayne Mountjoy and William Qoss,

analysts.

Aj. Fnsion-leach separation of vanadium; Claude Huffman, analyst. 

B. Fusion-leach separation of vanadium; Frank Qrimaldi, analyst.

TABLE 7. Comparison of vanadium recovery by two methods, in 

percent, when iron content ^6263) of shale is less than 5 percent

[A, analysis by frsion-leach, first method; Wayne Mountjov and William Qoss. 

analysts; Aj, by simple carbonate fusion of cupferratos, Wayne Mountjoy and 

William Goss, analysts. Add 259500 to all sample numbers, except 04 to which 

add 259600, to form serial numbers]

Sample

37 

93 

72 

83 

28 

57 

60 - 

75 

77 

89 

50 

04. ..

30 

90 

53 

97 

33 .

A

O OO9

.003

.005

nn^

007

.008

.010

.010

.015

.016

.016

.021

.018

.020

Aj

<0.001

.003

003

.005

007

.007

OOQ

.010

.010

.012

ni q

.014

.014

.015

.015

.016

Difference

ft ftho

.002

.001

AA1

fiftO

.002

ft09

.006

flftO

002

.006

.003

.004

Sample

51- 

36 

38 

 }Q

94 

81 

29 

85 ------

47 

55 

74. .

63 

27. 

61 

48 

26 

A

0.018

.017

.017

.020

.021

.020

.022

.020

.031

.030

.034

.056

.055

.058

.064

A3

0.017

.019

.019

.018

.019

.020

.021

.022

.022

.024

.030

.034

.055

.055

.056

.067

Difference

0.001

.002

.002

.002

.002

None

.001

.002

.003

.007

.001

None

.002

.003

Standard deviation, all samples___-----_..___-...-__.... 0.0018

CHROMIUM, FUSION-LEACH CHBOMATB METHOD

[Range in shale: 0.001 to 0.05 percent chromium] 

PRINCIPLES

The sample is fused with a mixture of potassium 

carbonate and potassium chlorate to convert chromium 

to chromate whose absorbance is determined at 370 m/u. 

Potassium nitrate cannot be used as the oxidant because 

any nitrite present or formed during the fusion absorbs 

strongly at 370 nijn and interferes. Chlorate and such 

products as perchlorate or chloride, however, do not 

absorb at this wavelength. The dissolution of platinum 

is kept to a minimum by carefully controlling the temperature and limiting the time of fusion. Small amounts 

of dissolved platinum are precipitated either as metal or 

oxide on digestion of the melt with water containing 

some alcohol. On filtering the solution, some iron may 

pass the filter in a colloidal state and subsequently interfere. A second digestion and filtration of the solution 

may be required to overcome this interference. Colored 

extractable compounds in filter paper are removed by 

washing the paper with potassium carbonate solution. 

Glassware should be cleaned with nitric acid; the use 

of dichromate-sulfuric acid cleaning solution should be 

avoided. A blank is carried through all steps of the 

procedure.

In genera], the method is suitable for determining 

chromium in concentrations greater than 10 ppm. 

When less chromium is to be determined, some difficulty may result from stray yellow colors of unknown 

source that tend to give erratic results. Possibly substitution of silver crucibles for platinum in the fusion 

may overcome this. If silver is substituted, a lower 

temperature melting flux made by mixing sodium carbonate, potassium carbonate, and potassium chlorate in 

the proportions 25:25:1 by weight must be used, and the 

temperature of the fusion should not exceed 750°C.

APPARATUS AND REAGENTS

Beckman DU spectrophotometer supplied with 5-cm cells. 

Fusion mixture: Mix intimately 25 parts potassium carbonate

and 1 part ground potassium chlorate by weight. 

Potassium carbonate, 10 percent w/v: Prepare the solution fresh

as needed. 

Standard chromate stock solution, 1 ml=l mg Cr: Add 0.5656 g

potassium dichromate and 1.0 g potassium carbonate to water

in a volumetric flask. Dissolve the salts and dilute the

solution to 200 ml. 

Standard chromate, dilute solution, 1 ml =10 micrograms Cr:

Take 5 ml of stock solution add 1 g of potassium carbonate,

and dilute to 500 ml with water in a volumetric flask.

PROCEDURE

1. Transfer a 1-g sample to a platinum crucible and burn off the 

organic matter at 700° to 900° C. Carry a reagent blank 

through the entire method.
'CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-ll

2. Add 5 g of fusion mixture to the crucible, mix intimately with 

the sample, and sprinkle a cover of 0.5 to 1 g more of fusion 

mixture over the charge. Cover the crucible with platinum 

lid.

3. Heat the charge gradually over a burner to the fusion point 

and keep molten at lowest possible temperature for at least 

5 minutes. Too high a temperature in the fusion should be 

avoided to minimize attack of the platinum crucible.

4. Transfer the crucible and contents to a small beaker and add 

35 to 50 ml of water and a few drops of alcohol (more if 

required to reduce manganate). Digest the solution on a 

steam bath, breaking up all lumps, until the precipitate is 

filterable. Cool the solution in an ice bath.

5. Filter the chilled solution into a beaker, using a dense filter 

paper previously washed with 10 percent potassium carbonate solution to remove the extractable colored compounds 

from the paper. Wash the residue with 0.1 percent potassium carbonate solution.

6. Place the filtrate on a team bath and evaporate the solution 

to about 70 ml. If the solution does not require evaporation, cover the beaker and heat for about 30 minutes. If 

no precipitate forms, cool the solution, transfer to a 100-ml 

volumetric flask, and dilute to volume. If a precipitate 

forms (generally owing to iron that has leaked through the 

filter paper in a colloidal state during filtration), chill the 

solution in an ice bath and filter it again through a prewashed paper and wash briefly. Dilute the solution to 100 

ml in the volumetric flask.

7. Determine the absorbance of the solution at 370 m/i against 

water as reference.

8. Calculate the percentage of chromium in the sample.

STANDARD CURVE

Transfer aliquots of standard chromate solution containing 0, 20, 50, and 100 micrograms Cr to 100-ml 

volumetric flasks. Adjust to 100-ml volume with 

water and determine the absorbance of the solution at 

370 m/i against water as a reference, using 1- or 5-cm 

cells.

PRECISION OF CHROMIUM DETERMINATIONS

Chromium was determined on the 80 samples of shale 

in laboratory B by the chromate method described. 

The ranges of concentration for chromium in the shale 

were from 0.00005 to 0.0005 percent (6 samples); 0.0005 

to 0.005 percent (3 samples); 0.005 to 0.05 percent (71 

samples). Standard deviations for the analytical work, 

tables 8, 9, and 10, apply only to the range 0.005 to 0.05 

percent chromium.

A plastic clay (National Bureau of Standards, standard sample 98), with a certificate value 0.014 percent 

chromium, was analyzed for chromium with each set of 

analyses during the course of the work by laboratory B. 

Results of 0.0146, 0.0148, 0.0149, 0.0144, 0.0143, 

0.0145, 0.0144, and 0.0144 percent chromium were 

obtained.

The differences in chromium concentration reported 

in table 10 are shown graphically in figure 3.

2250 2250

CHROMIUM, IN PARTS PER MILLION 

LABORATORY A

CHROMIUM, IN PARTS PER MILLION 

LABORATORY F

2250

250

CHROMIUM, IN PARTS PER MILLION 

LABORATORY G

FIGURE 3. Comparison of chromium determinations of B with those of A, F, and O

TABLE 8. Replicate determinations l of chromium, in percent,

made in laboratory B by one chemist 

[Analysis by chromate method, Ivan Barlow, analyst. Add 259600 to all sample

numbers, except 00 to 05 to which add 259600, to form serial numbers] 

60-.----- _-- -... 0.0056 0.0062

29.. ................. .0087 .0089

34... .- . _.. .0096 .0099 

69............._.___ .010 .010

86.. .___ _----..... 0.010 0.012

04-.-....... ......... .010 .010

49..................... .013 .013

73-.-..-_........._. .013 .013

1 Precision and reliability of determinations in the range 0.005 to 0.05: standard deviation, 0.0005; number of comparisons, 8.

TABLE 9. Determinations l of chromium, in percent, in hidden 

splits by laboratory B

[Analysis by chromate method; Ivan Barlow, analyst. Add 259500 to all sample 

numbers, except 00 to 05 to which add 259600, to form serial numbers. Groups 

indicate the samples that were duplicates]

33....-..... ... 0.0056 53.. ._.._.-. .. 0.010 80.... -.- 0.010 

97- . . .0053 04 .. .010 00.. .- .010

49.

03.

.013

.013

.014

.013

65.

01.

.0095

.010

.014

.013

.0095

.0096

.011

.012

1 Precision and reliability of determinations hi the range 0.005 to 0.05: stai dard deviation, 0.00034; number of comparisons, 13.

TABLE 10. Determinations l of chromium, in percent, in check

samples 

[Add 253500 to each sample number to form serial number]

Sample

28... .......

33-. 

37-..... 

39... ...

46-.-- 

48.... ..............

49... 

63.--.. .......... 

92...- ......... ......

94.. ...... ...........

B

0.0075 

.0056 

<.0003 

.0077 

.011 

.0004 

.013 

.014 

.012 

.011

A

0.0056 

.0053 

.0006 

.0091 

.010 

.0023 

.013 

.015 

.013 

.011

F

0.0065 

.0053 

.0003 

.0064 

.0034 

.0012 

.012 

.013 

.011 

.0095

G

0.0058 

.0047 

.0003 

.0054 

.011 

.0010 

.013 

.016 

.010 

.015

Mean

0.0064 

.0052 

<.0004 

.0072 

.010 

.0012 

.013 

.015 

.012 

.012

1 Precision and reliability of determinations in the range 0.005 to C 

Standt 

deviiti 

B, A.. O.C

B, F ........ ..... .... ...... .... ....... .C

B, G......... . ... ... .C

3. Analysis by chromate method; Ivan Barlow, analyst. 

A. Analysis by chromate method; Claude Huffman, analyst. 

?. Spectrographic analysis; Paul Barnett, analyst. 

G. Spectrographic analysis; Harry Rose and Sol Berman, analysts.

Difference (max 

min)

0.0019 

.0009 

.0006 

.0037 

.0016 

.0019 

.001 

.013 

.003 

.006

Standard deviation

0.00092 

.00044 

.00029 

.0018 

.00078 

.000^2 

.00049 

.0015 

.0015 

.0029

.05: 

ird Number of 

on comparisons 

1008 10 

1007 10 

1013 10
A-12 ANALYTICAL METHODS IN GEO CHEMICAL INVESTIGATIONS OF THE PIERRE SHALE

MANGANESE, PERSULFATE OXIDATION METHOD

[Kange in shale: 0.001 to 5 percent manganese] 

PRINCIPLES

Manganese is oxidized to permanganate by several 

oxidizing agents in acid solution. For oxidation of 

small amounts of manganese, persulfate in the presence 

of a small amount of silver nitrate is the preferred reagent (Nydahl, 1949) and (Sandell, 1950, p. 433). The 

oxidation is usually carried out in a medium of 0.3M 

nitric acid and at least O.lM phosphoric acid. The 

addition of mercuric sulfate prevents the interference 

of small amounts of chloride by forming slightly dissociated mercuric chloride.

APPARATUS AND REAGENTS

Beckman DU or Model B spectrophotometer, adapted for both 

1- and 5-cm cells.

Mercuric sulfate-silver nitrate solution: Dissolve 33 g of mercuric sulfate in 147 ml of 1 + 1 nitric acid and 200 ml of water, 

add 110 ml of 85 percent phosphoric acid and 17 mg silver 

nitrate and stir to dissolve. Cool and dilute to 500 ml with 

water.

Standard manganese stock solution, 1 ml=l mg Mn: Heat manganese sulfate monohydrate at 500° C to convert to the anhydrous form. Dissolve 0.5498 g of anhydrous manganous sulfate in 50 ml of 1 + 99 nitric acid and dilute to 200 ml with 

1 + 99 nitric acid in a volumetric flask.

Standard dilute manganese solution A, 1 ml = 10 micrograms Mn: 

Take 5 ml of stock solution and dilute to 500 ml with 1 + 99 

nitric acid.

Standard dilute manganese sulution B, 1 ml=50 micrograms Mn: 

Take 25 ml of stock solution and dilute to 500 ml with 1+99 

nitric acid.

Nitric acid, 1 + 99: Dilute 10 ml nitric acid to 1 liter.

PROCEDURE

1. Transfer a 0.7- to 1.0-g sample to a 50- to 75-ml platinum 

dish. Remove organic matter by igniting gently at first 

and raising the temperature gradually to about 700°C.

2. Moisten the sample with water and add 5-10 ml nitric acid, 

10 ml hydrofluoric acid, and 2-5 ml perchloric acid to the 

dish.

3. Cover the dish and digest the solution on a steam bath for 

30 minutes.

4. Remove the cover from the dish and evaporate the solution 

to fumes of perchloric acid. Repeat steps 2 to 4 if the 

sample is not thoroughly decomposed.

5. Cool the dish, add 10 ml of water, rinsing down the sides of 

the dish, and evaporate the solution to fumes of perchloric 

acid. Repeat, but this time take to complete dryness, expelling all acid at 200°C to 220°C on a hot plate.

6. Wet the residue in the dish with 2 ml 1 + 1 nitric acid and 

evaporate to dryness on the steam bath.

7. Add exactly 2.0 ml 1 +1 nitric acid to the dish and allow to 

stand a few minutes at room temperature. Add 18 ml 

water to the dish, cover, and digest to dissolve the residue. 

If a clear solution is obtained, transfer the solution to a 

a 100-ml volumetric flask and dilute to volume with water.

8. If a residue remains undissolved, filter the solution into a 

100-ml volumetric flask, wash the residue with water and 

reserve the filtrate.

9. Ignite the residue and paper in a crucible and fuse the residue 

with 0.5 g of sodium carbonate. Cool the crucible, add 

5 ml water, and carefully neutralize the carbonate by 

adding exactly 1.2 ml 1 + 1 nitric acid to convert the 0.5 g 

of sodium carbonate to carbonic acid and sodium nitrate. 

Warm the solution briefly to expel carbon dioxide, cool, 

and transfer this solution to the reserved portion in the 

100-ml flask and dilute to volume with water. The solution is now 1 percent, by volume, nitric acid.

10. Transfer a 25-ml aliquot of the solution to a 125-ml Erlenmeyer flask. If smaller aliquots are required, dilute the 

aliquot to 25 ml with 1 + 99 nitric acid.

11. Add 0.5 ml 1 + 1 nitric acid, 19.5 ml of water, and 3 ml of 

the mercury-silver solution; stir the solution.

12. Add 1.0 g ammonium persulfate to the flask and heat over 

a flame just to boiling. Set the hot flask aside for 1 minute, then cool quickly in a cold-water bath until room 

temperature is reached.

13. Transfer the solution to a 50-ml volumetric flask and dilute 

to volume with water that has previously been boiled with 

ammonium persulfate and cooled.

14. Determine the absorbance of the solution at 525 m/u against 

a reagent blank carried through the method.

15. Calculate the percentage of manganese in the sample.

STANDARD CURVE

Pipet aliquots of standard manganese solution equivalent to 0, 10, 20, 40, 80, and 100 micrograms manganese 

and transfer to 125-ml flasks. These concentrations 

are suitable for establishing a standard curve for a 

5-cm cell. If greater concentrations are to be determined using a 1-cm cell, aliquots containing 50, 100, 

200, 400, 800 and 1,000 micrograms manganese are 

used. Develop the color-of the solutions, with due 

regard for the proper acidity, by following the procedure 

steps 10 to 14. Draw standard curves for use with the 

method.

PRECISION OF MANGANESE DETERMINATIONS

Manganese was determined on the 80 samples in 

laboratory A by the method described. The ranges 

of concentration for manganese were from 0.005 to 0.05 

percent (59 samples), 0.05 to 0.5 percent (17 samples), 

and 0.5 to 5.0 percent (4 samples). The results of 

replicate determinations are give in table 11, those on 

the hidden splits in table 12, and those on the check 

samples in table 13. Ordinarily laboratories C and D 

report manganese in the range below 0.1 percent MnO 

only to the nearest hundredth of a percent. However, 

the original notebook data of laboratories C and D 

were converted from MnO to Mn and reported to two 

significant figures for the comparative evaluation of the 

following tables. The results of A are compared with 

those of B, C+D, and F in figure 4.
CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-13

480

MANGANESE. IN PARTS PER MILLION 

LABORATORY B

MANGANESE, IN PARTS PER MILLION 

LABORATORY C + D

480

MANGANESE, IN PARTS PER MILLION 

LABORATORY F

FIGURE 4. Comparison of manganese determinations of A with those of B, C+D

and F.

TABLE 11.^-Determinations 1 of manganese, in percent, by three 

laboratories

[Add 259500 to all sample numbers, except 03 and 04 to which add 259600, to form serial

numbers]

26 

63 

81 

57 

65 

77.. .

78 

59 

75 

43 

56 

47 

68 

42 

58 

79 

41 

33 

A

0.009 0.009

.008 .009

.008

.015

. 021 . 026

.021

.022

.024 .024

.024

.033

.035

.040

.044 .044

.052

.068

.14 .14

2. 2 2. 2

3. 4 3. 5

C"

0.012

.012

.015

.016

.025

.024

.026

.026

.028

.033

.035

.039

.043

.053

.069

.13

2.2

3.6

73 

61 

27 

03 

93 

87 

99 

30 

84 

74 

90 

91 

72 

50 

89 

95 

39 

40 

32 

69 

76 

52...

A

0.005 0.007

. 007 . 008

. 008 . 010

. 010 . 016

.012

.012

.013 .013

.013 .014

. 013 . 016

.015 .017

.015

.016

.019

.020

. 022 . 022

.022

. 024 . 026

.025

. 025 . 026

.026

.027

.028

D2

0.015

.007

.014

.020

.018

.020

.018

.017

.022

.022

.018

.018

.022

.031

.026

.026

.029

.023

.024

.025

.036

.033

62 

70 

71 

66 

55 

46...

34...

67 

44...

45 

85 

54 

29 

51 

04 

64...

35 

36...

60 

31 

28 

38 

A

0.029 0.030

.029

. 029 . 030

.032

.033

. 034 . 035

.040 .040

.043

.047

.050

.050

.052

. 056 . 058

.084

. 085 . 086

.089

.12 .12

.15

.19

.23 .24

.42 .42

.92 .96

D*

0.031

.027

.031

.036

.036

.042

.042

.053

.051

.050

.057

.054

.058

.090

.089

.086

.12

.15

.19

.24

.42

.91

1 Precison and reliability of determinations:

A...... .... ...

A, C 

A, D.... .....

Range

0. 005 to 0. 05

Standard 

deviation

0.0014 

.0021 

.0037

Number of comparisons

20 

18 

46

0.05 to 0.5

Standard 

deviation

0. 0032 

.0050 

.0025

Number of comparisons

6 

4 

17

0.5 to 5

Standard 

deviation

0.043 

.079 

.025

Number of comparisons

3

4 

2

2 Reported MnO calculated to Mn: For reported values of 0.09 MnO (0.070 percent 

Mn) and less the last figure is the result of the calculation.

A. Persulfate method; Dwight Skinner, analyst.

C. Standard rock analysis, periodate method; Marguerite Seerveld and Vertie Smith, analysts. 

D. Periodate method, Shapiro and Brannock, 1956; Leonard Shapiro, Paul Elmore,

Samuel Botts, and Marvin Mack, analysts.

592016 O 61 3

TABLE 12. Determinations 1 of manganese, in percent, in hidden

splits

[Add 259500 to all sample numbers, except 00 to 05 to which add 259600. to form 

serial numbers. Groups indicate the samples that were duplicates]

Sample

33 

97.. _ ........

49. 

99 

03 

53 

04 

65 

98. 

A

3.5

3.4

.014

.014

.013

.013

.084

.086

.024

.025

O

3.6

.016

.016

.084

.025

D

3.4

.018

.020

.089

.035

Sample

68 

01 

80 -

00 

82 

02 

86 - __

05 

A

0.044

.041

.047

.051

.028

.028

.020

.018

O

0.043

.048

.030

.022

D

0.052

.049

.035

.023

1 Precision and reliability of determinations:

A 

A, C+D... .

Range

0. 005 to 0. 05

Standard deviation

0. 0013 

.0034

Number of comparisons

11 

36

0. 05 to 0. 5

Standard deviation

0.0021

Number of comparisons

4

0. 5 to 5

Standard deviation

0.086

Number of comparisons

4

A. Persulfate method; Dwight Skinner, analyst.

O. Standard rock analysis, periodate method; Marguerite Seer veld and Vertie Smith,

analysts. 

D. Periodate method (Shapiro and Brannock, 1956); Leonard Shapiro, Paul Elmore,

Samuel Botts, and Marvin Mack, analysts.

TABLE 13. Determinations l of manganese, in percent, in check

samples

[Add 259500 to each sample number.to form serial number]

Sample

OQ33 

37 

39

46 

48

49

63 . 

09

<U

A

0 49

3.5

.022

.025

.035

O94

.009

.010

.015

B

O M.

3.5

.016

.025

.033

.022

.012

.005

.010

.014

O

.025

.016

.012

D

0.42

.020

.029

.042

.017

.020

F

0.023

.035

.045

.027

.020

.007

.012

.017

Mean

0.43

3.5

.020

.029

.039

.025

.016

.008

.012

.017

Difference (max 

min)

0.02

.1

.007

.010

.012

.005

.008

.007

.007

.006

Standard deviation

0.012

.059

.0034

.0049

.0058

.0024

.0039

.0034

.0034

.0029

i Precision and reliability of determinations in the range 0.005 to 0.05:

Standard Number of

deviation comparisons

A, B 0.0020 8

A, C + b. -0031

A, F. .0040

A. Persulfate method; Dwight Skinner, analyst.

B. Persulfate method; Charles Kinser, analyst.

O. Standard rock analysis, periodate method; Marguerite Seerveld and Vertie Smith,

analysts. D. Periodate method (Shapiro and Brannock, 1956); Paul Elmore, Samuel Botts,

and Marvin Mack, analysts. 

F. Spectrographie method; Paul Barnett, analyst.

COBALT, DITHIZONB-NITROSO-R-SALT METHOD

[Range in shale: 0.0005 to 0.005 percent cobalt] 

PRINCIPLES

Cobalt is isolated by extraction of the dithizone 

complex in carbon tetrachloride from ammoniacal citrate solution according to Sandell and Perlich (1939). 

The cobalt is determined spectrophotometrically with
A-14 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALEi

nitroso-R-salt (l,nitroso, 2,hydroxynaphthalene, 3,6,disulfonate) in the presence of a citrate-phosphate-borate 

medium according to McNaught (1942). Copper, 

lead, zinc, and part of the nickel coextract with the 

cobalt in the dithizone separation. Interferences from 

these elements while determining cobalt in shale with 

the nitroso-R-salt method are a minimum because of 

the relatively small amount of copper, lead, zinc, and 

nickel found in shale. In addition, the nitroso-R-salt 

procedure will tolerate at least 10 mg iron, 5 to 10 mg 

copper, 0.2 mg nickel, and milligram amounts of manganese, zinc, cadmium, lead, and tin.

APPARATUS AND REAGENTS

Beckman DU spectrophotometer.

Citric acid, 50 percent w/v: British Drug House purified reagent

or the equivalent.

Dithizone, 0.05 percent w/v in carbon tetrachloride. 

Nitroso-R-salt, 0.05 percent aqueous solution. 

Citric acid, 0.20M: Dissolve 4.2 g of citric acid monohydrate to

give 100-ml aqueous solution. 

Buffer solution, 6.2 g of boric acid, 35.6 g of disodium hydrogen

phosphate heptahydrate, and 20 g of sodium hydroxide in a

total volume of 1 liter aqueous solution. 

Standard cobalt stock solution, 1 ml=l mg Co: Dissolve 0.8074

g cobaltous chloride hexahydrate in 200 ml total volume

aqueous solution containing 2-ml hydrochloric acid. 

Standard cobalt solution, 1 ml=10 micrograms Co: Take 5 ml

of cobalt stock solution and dilute to 500 ml with water in a

volumetric flask. 

Thymol blue indicator 0.1 percent: Take 0.1 g of thymol blue

and dissolve it in 25-ml ethyl alcohol. Dilute to 100 ml

with water.

PROCEDURE

1. Weigh a 1.0-g sample into a 50- to 75-ml platinum dish. 

Ignite organic matter at about 700°C. Carry a reagent 

blank through all steps of the procedure.

2. Moisten the sample with water. Add 10 ml hydrofluoric 

acid, 10 ml nitric acid, and 4 ml perchloric acid to the 

dish. Heat the solution 30 minutes on a steam bath with 

the dish covered with a platinum cover. Remove cover 

and evaporate the water. Heat the solution to fumes of 

perchloric acid. Cool. Add 5 ml water and fume again. 

Repeat. Fume the solution to moist dryness; avoid 

heating the solution to complete dryness.

3. Add 2 to 4 ml 1 + 1 hydrochloric acid and 10 ml water to the 

dish and digest to dissolve the salts. If undecomposed, 

sample is present, it should be filtered off and the filtrate 

reserved. The residue is ignited and fused with about 

0.5 g sodium carbonate and dissolved in 1 + 1 hydrochloric 

acid using 1.6 ml for every 0.5 g sodium carbonate used. 

The solution is combined with that reserved.

4. Evaporate the solution if necessary so that it can be transferred and made to 25 ml in a volumetric flask. Potassium 

perchlorate may precipitate on cooling. Disregard.

5. After any salts settle out transfer a 10-ml aliquot of solution 

to a small separatory funnel and add 5 ml of 50 percent 

w/v citric acid. Add 0.2 ml thymol blue indicator and 

neutralize the solution with ammonium hydroxide to a 

pH of 8.5 to 9.3 (intermediate color of thymol blue).

Preferably a pH meter should be used and the pH of the 

solution adjusted to 9.0.

6. Add 5 ml dithizone, shake the solution vigorously for 1 

minute, and draw off the carbon tetrachloride layer. 

Continue extracting the solution with 5 ml portions of 

dithizone solution until the last portion still shows a green 

color after shaking for 1 minute. Three to four extractions usually are required.

7. Wash the combined carbon tetrachloride extracts with 5 ml 

of 1 + 99 ammonium hydroxide. Transfer the carbon 

tetrachloride solution of cobalt to a 50-ml beaker and carefully evaporate the carbon tetrachloride by heating the 

beaker on a water bath.

8. Add 0.25 ml sulfuric acid and 0.25 to 0.5 ml perchloric acid to 

the beaker and heat at 200° to 250° C until the liquid is 

entirely colorless. Then fume off the sulfuric acid completely, including any drops that may have condensed on 

the upper portions of the beaker. The temperature should 

be less than 500°C.

9. Add 1 ml of 1 + 1 hydrochloric acid, swirl the beaker to wet 

the surface of the beaker with acid, wash down the sides 

with a minimum of water from a wash bottle and evaporate 

the solution to dryness. Finish the evaporation by heating 

the beaker in an oven at 140° C to drive off any acid that 

may have condensed on the sides of the beaker.

10. Add to the beaker 1.0 ml of 0.2M citric acid solution, and 

1.2 ml of phosphate-borate buffer solution. Stir the solution while adding exactly 2 ml of nitroso-R salt solution. 

Boil the solution for 1 minute.

11. Add 1.0 ml nitric acid, and boil the solution again for 1 minute. Adjust the volume of the solution to 10 ml in a volumetric flask. Obtain the absorbance of the solution at 

475 m/z against a blank solution as a reference. The blank 

solution is prepared by adding to a beaker 1.0 ml of citric 

acid, 1.2 ml of phosphate-borate buffer, 2 ml of nitroso-Rsalt and boiling the solution for 1 minute; adding 1.0-ml 

nitric acid and again boiling for 1 minute; cooling the 

solution in the dark and adjusting the volume to 10 ml in 

a volumetric flask.

12. Calculate the percentage of cobalt in the sample.

STANDARD CURVE

Transfer aliquots of standard cobalt solution containing 0, 3, 5, 15, and 30 micrograms of cobalt to small 

beakers. Evaporate the solution to dryness to remove 

mineral acid and proceed with steps 10 and 11 of the 

procedure.

PRECISION OP COBALT DETERMINATIONS

Cobalt was determined on the 80 samples of shale in 

laboratory B with the nitroso-R-salt method described. 

The concentration of cobalt was in the range 0.0005 to 

0.005 percent for all 80 samples. Only two replicate 

determinations were reported (table 14). The results 

of determinations on the hidden splits are given in table

15. Two separate analyses for cobalt in the check 

samples were made in laboratory A, with results also 

reported by B, F, and G except that G did not report 

cobalt in two samples. These data are given in table

16. Figure 5 compares the data of table 16 graphically.
/GHEIMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-15

COBALT, IN PARTS PER MILLION 

LABORATORY A

COBALT, IN PARTS PER MILLION 

LABORATORY A,

COBALT, IN PARTS PER MILLION 

LABORATORY f

COBALT, IN PARTS PER MILLION 

LABORATORY G

FI&UBE 5. Comparison of cobalt determinations of B with those of A Ai, F, and G. ; 

Plots that coincide are indicated with the number involved.

TABLE 14. Replicate determinations of cobalt, in percent, made 

in laboratory B by one chemist

[Analysis by nitroso-K-salt method; Joseph Dinnin, analyst. Add 259500 to each

sample number to form serial number] 

37.-- . 0.0005, 0.0006

40----------___.___-_ .__--_--__...._-- .0013, .0014

TABLE 15. Determinations 1 of cobalt, in percent, in hidden splits

by laboratory B 

[Analyses by hitroso-R-salt method; Joseph Dinnin, analyst. Add 259500 to

all sample numbers, except 00 to 05 to whi?.h add 259600, to form serial numbers.

Groups indicate the samples that were duplicates]

33 - 0.0018 53 , 0.0015 80- - -- 0.0017 

97 .0015 04., .0013 00 .0018

03-

.0020

.0019

.0021

.0020

65-

01-

.0014

.0013

.0018

.0018

82-.-_..._. .0027 

02 .. .0029

05.

.0016

.0015

i Precision and reliability of determinations in the range 0.0005 to 0.005: standard 

deviation, 0.00010; number of comparisons, 13.

TABLE 16. Determinations 1 of cobalt, in percent, in check samples 

'[Add 259500 to each sample number to form serial number]

Sample

28 

33 - 

37 

39 

46 

48 

49 

63 

92 

94 

B

0.0009

.0018

.0006

.0012

.0023

.0017

.0020

.0006

.0010

A

0.0006

.0010

.0002

.0007

.0018

.0009

.0013

.0002

.0010

.0007

A,

0.0009

nrtno

.0003

.0008

.0019

.0013

.0017

.0004

.0011

0008

F

0.0012

.0022

.0004

.0011

.0027

.0020

.0004

.0015

.0011

G

0. 0010

.0015

.0010

.0020

ftfi19

.0013

.0012

.0011

Mean

0.0009

.0015

0004

.0010

.0021

.0014

.0017

.0004

flflflQ

Difference (max 

mini

0.0006

.0013

.0004

.0005

.0009

.0009

.0007

.0004

fifing

.0004

Standard deviation

0. 00026

. 00056

.00019

.00022

.00039

.00039

. 00030

.00019

.00022

.00017

1 Precision and reliability of determinations in the range 0.0005 to 0.005:

Standard Number of 

deviation comparisons

B, A 0.00043

B, Ai .00029

B, F ... .00016

B, G.--.-.. .00026

All data. .. .00031

B. Nitroso-R-salt method; Joseph Dinnin, analyst.

A. Nitroso-R-salt method; Howard Lipp, analyst.

Ai. Nitroso-R-salt method; Howard Lipp and Claude Huffman, analysts.

F. Spectrorraphic method; Paul Barnett, analyst.

G. Spectrographic method; Harry Rose, analyst.

NICKEL, DIMETHYLQLYOXIME METHOD 

PERSULFATE OXIDATION

[Range in shale: 0.0005 to 0.05 percent nickel] 

PRINCIPLES

Nickel is concentrated and separated from rockforming elements by extraction of the nickelous 

dimethylglyoxime complex from an ammoniacal citrate 

solution with chloroform. The citrate solution prevents the precipitation of iron, aluminum, and other 

metals. Some copper accompanies nickel in the extraction, but it is removed by washing the extract 

with dilute ammonia. According to Sandell (1950, 

p. 469) much manganese interferes by preventing 

complete extraction of nickel. This interference can 

be prevented by adding hydroxylamine hydrochloride 

to keep manganese in the bivalent state. Nickel is 

returned to the aqueous phase by stripping with 0.57V 

hydrochloric acid. The solution containing nickel is 

made strongly basic, pH 12 to 13, in the presence of 

sodium citrate. The nickel is oxidized with potassium 

persulfate to form the colored nickelic dimethyglyoxime complex whose absorption is measured. The nickel 

complex formed under these conditions is complex B, 

of constant and reproducible composition (Furman 

and McDuffie, 1947). The effect of pH and concentration of persulfate on the color reaction was studied 

by White (1952) and by Bane and Grimes (1950, 

p* 435).

APPARATUS AND REAGENTS

Beckman DTJ spectrophotometer supplied with 1- and 5-cm cells. 

Dimethylglyoxime solution: Dissolve 1 g of dimethylglyoxime

in 100-ml ethyl alcohol in a volumetric flask. Stopper. 

Sodium citrate, 10 percent in water, w/v. 

Potassium persulfate, 10 ml=0.5 g: Dissolve 50 g of reagent

grade potassium persulfate in water by heating and stirring.

Cool, and dilute to 1 liter. 

Chloroform, reagent grade. 

Standard nickel stock solution, 1 ml=l mg Ni: Dissolve 0.81 OOg

nickel chloride hexahydrate with 5 ml hydrochloric acid and

water. Dilute to 200 ml in a volumetric flask. 

Standard nickel, dilute solution, 1 ml= 10 micrograms Ni: Take

5 ml of stock solution and dilute to 500 ml with water in a

volumetric flask. 

Hydrochloric acid Q.5N: add 21 ml hydrochloric acid to water

and dilute to 500 ml. 

Ammonium hydroxide, 2 percent v/v. 

Hydroxylamine hydrochloride, crystals. 

Sodium hydroxide, 50 percent solution: Add 500 g sodium

hydroxide to 500 ml water, shake to dissolve, cool, and allow

carbonates to settle out.

PROCEDURE

1. Weigh 1 to 2 g of sample and transfer to a 100-ml platinum 

dish. Ignite organic matter at 500° to 600°C in a muffle.

2. Moisten the sample with water and add 5 ml nitric acid, 

10 ml hydrofluoric acid, and 5 ml perchloric acid. Cover 

the dish and heat the solution 30 minutes on the steam
A-16 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALE\

bath. Remove cover and evaporate the solution to remove 

water. Fume the solution to moist dryness on a hot plate. 

Add acids as mentioned above and repeat the operation.

3. Add 50 ml water and 10 ml hydrochloric acid to the dish, 

and digest to dissolve the salts. Transfer the solution to a 

100-ml volumetric flask with water. Dilute to volume 

and mix. If undecomposed sample is present after digesting the solution, filter it off, ignite, and fuse with about 

0.5 g of sodium carbonate. Dissolve the cake in 1 + 1 

hydrochloric acid, using 1.6 ml for every 0.5 g sodium 

carbonate used. Combine solution with the reserved filtrate and dilute to 100 ml in a volumetric flask.

4. Take a 10- or 25-ml aliquot of solution and transfer it to a 

60-ml separatory funnel. If less than a 25-ml aliquot is 

taken, make up the difference with water. Add 10 ml of 

sodium citrate solution (more if needed to keep Fe and Al 

in solution), and ammonium hydroxide until the solution 

is slightly ammoniacal. Adjust the pH to 9.0 or just 

pink to phenolphthalein vuth diluted ammonium hydroxide 

or hydrochloric acid.

5. Add a few crystals of hydroxylamine hydrochloride and 3 

ml of dimethylglyoxime solution to the funnel. Shake 

the solution and allow to stand a few minutes.

6. Extract the solution twice with 10 ml chloroform each time, 

drawing the chloroform layer into a separatory funnel 

reserved for this purpose.

7. Shake the combined chloroform extracts with 10 ml of 1 + 49 

ammonium hydroxide, and draw the chloroform into 

another separatory funnel. Shake the aqueous phase with 

3 ml of chloroform for 30 seconds and combine the chloroform layer with the washed chloroform extract.

8. Extract the chloroform solution with two separate 10-ml 

portions of 0.5AT hydrochloric acid and vigorously shake 

. each portion for 1 minute. Transfer the hydrochloric acid 

solutions to a 50-ml volumetric flask by filtering through a 

7-cm dense paper. Reject the chloroform. Wash the funnel 

by shaking with about 3 ml of water, filtering the water 

into the flask containing the acid solution of the nickel. 

Wash the filter paper once with water.

9. Add 2 ml sodium citrate solution to each flask and make the 

solutions strongly basic (pH 12 or more) by adding 12 to 

15 drops of sodium hydroxide solution (50 percent w/v) to 

each.

10. Add 10 ml potassium persulfate solution and 3 ml dimethylglyoxime solution to each flask.

11. Dilute to 50-ml volume with water, mix, and then, after 

waiting 0.5 to 1 hour to develop full color, determine 

absorbance in 5-cm cells at 530 m/*. A blank carried 

through the method, beginning at step 4, is used as the 

reference solution.

12. Calculate the percentage of nickel in the sample.

STANDARD CURVE

Transfer aliquots of standard solution containing 0, 

5, 10, 20, 40, and 60 micrograms of nickel to separatory 

funnels. Add a few drops 1 + 1 hydrochloric acid to 

each, dilute to 25 ml with water, and proceed with steps 

4 through 11 of the procedure.

ALTERNATIVE BROMINE OXIDATION

[Range In shale: 0.0005 to 0.05 percent nickel] 

PRINCIPLES

In the dimethylglyoxime method (Sandell and Perlich, 1939), the nickelic dimethylglyoxime is formed 

from slightly ammoniacal solution, using bromine as the 

oxidant (Rollet, 1926). The absorbance of the complex is determined within 5 minutes and at 450 m/u 

instead of at 530 m/u. The change in the color intensity with time, in this system, is due to complex A 

changing to complex B (Furman and McDuffie, 1947). 

In ammoniacal solutions of pH 9 to 10, complex A forms 

rapidly and then changes slowly to complex B, but at 

pH 10 to 11, the change to complex B is very rapid and 

results are not reproducible. Change in color intensity 

is partly overcome by making readings at 450 m/u, and 

the sensitivity also is increased at this wavelength 

(Mitchell and Mellon, 1945).

APPARATUS AND REAGENTS

The reagents and apparatus are given under the previous 

method for determination of nickel, except that a saturated 

solution of bromine in water is substituted for the potassium 

persulfate solution; the sodium hydroxide solution is not required.

PROCEDURE

1. Follow steps 1 through 8 of the previous procedure for the 

determination of nickel.

2. Add 2 ml of sodium citrate solution and 1 ml of saturated 

bromine water to each flask and allow the solution to stand 

for a few minutes. Then add ammonium hydroxide until 

the color of bromine is removed (the solution may not 

become entirely colorless, because enough dimethylglyoxime 

may be present to give a visible reaction with nickel). 

Add 1 ml ammonium hydroxide in excess.

3. Add 1 ml of dimethylglyoxime solution.

4. Dilute the solution to 50-ml volume with water and determine within 5 minutes the absorbance against water as a 

reference at 450 m/u. A reagent blank should be run with 

the samples.

5. Calculate the percentage of nickel in the sample.

PRECISION OF NICKEL DETERMINATIONS

Nickel was determined in the 80 samples in laboratory A with the dimethylglyoxime method, using persulfate as the oxidant. The ranges of concentration 

for nickel were from 0.0005 to 0.005 percent (46 

samples) and from 0.005 to 0.05 percent (34 samples). 

The results on 38 replicate determinations are given in 

table 17, those on hidden splits in table 18, and those on 

the check samples in table 19. Figure 6 shows the 

data of B and F plotted against that of A. In general, 

the agreement between laboratories is good.
CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-17

 200 Z 200 

O

200

NICKEL, IN PARTS PER MILLION 

LABORATORY B

200

NICKEL, IN PARTS PER MILLION 

LABORATORY F

FIGURE 6. Comparison of nickel determinations of A with those of Band F. 

that coincide are indicated with the number involved.

Plots

TABLE 17. Replicate determinations 1 of nickel, in percent, made 

in laboratory A by one chemist

[Analysis by persulfate oxidation method; Lewis Rader, analyst. Add 259EOO to all 

sample numbers, except 00 to 05 to which add 259600, to form serial numbers]

QQ n nnnti

41 0009

83 .0010

26 .0013

61- .0016

63 .0016

20 - .0016

73 .0019

QQ ftfiOJ.

27 .0026

81 - .0028

76 .0032

98 - - .0036

68 - .0038

1 Precision and re 

0.0005-0.005.

. 005- . 05 .

0.0006 

.0010 

.0011 

.0014 

.0016 

.0016 

.0016 

.0019 

.0024 

.0028 

.0032 

.0033 

.0037 

.0040 

liability

78 

00 

05 

28 

01 

91 

04 

03 

53 

99. .

49. 

43 

48 

- 0.0038

- .0040

- .0040

- .0041

- .0044

- .0058

. .0058

- .0059

- .0060

. .0064

. .0066

- .0068

- .0074

0.0039 

.0044 

.0043 

.0041 

.0046 

.0061 

.0062 

.0066 

.0060 

.0067 

.0068 

.0068 

.0076

56 

38 

58 

33

31 

51 

97

54 

55 

82 

02

of determinations: 

Range

- 0.0075

- - .0081

... .0084

-------- .0092

.... .0093

-- -- .0097

- .... .010

.011 

... ... .011

...... .015

 -_ .015

. .016

Standard Nur 

deviations comp 

0.00012 

.00035

0.0076 

.0083 

.0084 

.0094 

.010 

.0096 

.010 

.011 

.011 

.011 

.015 

.016 

.016

nber of 

arisons 

19 

26

TABLE 18. Determinations l of nickel, in percent, in hidden splits

[Analysis by persulfate oxidation method; Lewis Rader, analyst. Add 259500 to all 

sample numbers, except 00 to 05 to which add 259600, to form serial numbers. Groups 

indicate the samples that were duplicates]

33. . 0.0095 63 0.0060 80 0.0042 

97..._._------- .011 04-----_-_-.--___-_ .0060 00----------------- .0042

49.-.. .0067

96 .0061

99. - .0066

03. .0063

66. . .0037 

98---- - - .0037 02.

.0016

.0016

.0039 86.- .0041 

01 - - .0045 05.- - --- .0042

i Precision and reliability of determinations:

Standard Number of

Range deviations comparisons 

0.0005-0.005-.-. --- .................... 0.00019 5

.005- .06.- .00044 8

TABLE 19. Determinations 1 of nickel, in percent, in check samples 

[Add 259500 to all sample numbers, except 00 to 05 to which add 259690, to form serial

numbers]

Sample

28 . 

33... 

37... 

39.-. 

46.... -.

48-- 

49.... .......

63- 

92 

94... 

A

0.0041

.0095

.0035

-. 0055

.014

.0075

.0067

.0016

.0022

.0041

B

0. 0042

.0096

.0039

.0063

.015

.0073

.0071

.0016

.0022

.0037

F

0. 0038

.0090

.0039

.0056

.014

.0069

.0060

.0011

.0024

.0038

Mean

0. 0040

.0094

.0058

.014

.0072

.0066

.0014

.0023

.0039

Difference 

(max 

min)

0. 0004

.0006

.0008

.001

.0006

.0011

.0005

.0002

.0004

Standard 

deviation

0. 00024

. 00035

. 00024

. 00047

. 00059

. 00035

.00065

. 00030

. 00012

.00024

1 Precision and reliability of determinations:

A, B... _ A. F 

Range

0.0005 to 0.005

Standard 

deviation

0. 00018 

.00025

Number of 

comparisons

5

5

0.005 to 0.05

Standard 

deviation

0.00043 

. 00046

Number of 

comparisons

5 

5

A. Persulfate oxidation irethod: Lewis Rader, analyst.

B. Bromine oxidation, alternative irethod; Hyman Feinstein, analyst.

F. Spectrographic analysis; Paul Barnett, analyst.

COFFER, LEAD, AND ZINC 

ISCXLATION BY EXTRACTION

[Range in shale: Copper, 0.0003 to 0.010 percent; lead, 0.0003 to 0.0040 percent; 

zinc, 0.001 to 0.040 percent]

PRINCIPLES

Copper, lead, and zine are concentrated together 

by extraction of their dithizonates from a slightly basic 

citrate solution, pH 9.0, with a solution of dithizone 

in carbon tetrachloride, as described by San dell, 

(1937). Lead and zinc are stripped with dilute acid, 

leaving copper dithizonate in the carbon tetrachloride 

phase. The copper solution is evaporated, organic 

matter is destroyed, and the copper is determined 

either by dithizone or by the alternative 2,2' biquinoline 

method (cuproine). The aqueous phase containing 

lead and zinc is made to volume and separate aliquots 

are taken for the determination of lead and zinc by the 

dithizone methods described in this report.

REAGENTS

Dithizone, 0.05 percent (w/v), in carbon tetrachloride: Purify 

the dithizone by dissolving 0.5 g in 50 ml chloroform. Filter 

the solution through a coarse dry fritted-glass crucible to 

remove any insoluble material. Shake the solution in a 

separatory funnel with four successive 50 to 75 ml portions 

of 1 + 100 ammonium hydroxide, prepared from tank ammonia. 

Separate the aqueous extracts from the chloroform and filter 

through a small plug of cotton to remove droplets of chloroform. Make the ammoniacal solution slightly ' acid with 

redistilled hydrochloric acid to precipitate dithizone. Add 

about 15 ml of choroform and extract the dithizone. Add 

one or two more portions of chloroform and shake. Combine 

the chloroform extracts and shake the solution twice with an 

equal volume of water (redistilled or demineralized). Transfer 

the chloroform solution to a beaker and evaporate the chloroform at 50° C. Dry the product in a desiccator. Use a 

portion to prepare the 0.05 percent dithizone solution in 

purified carbon tetrachloride. The solution is stable if kept 

cold in a dark place.

Carbon tetrachloride: Distill in the presence of a little calcium 

oxide and collect the distillate in a clean, dry Pyrex bottle.

Water redistilled from a Pyrex glass still.

Hydrofluoric acid: Likely to contain lead and should be purified 

by distillation in a platinum or plastic still.

Hydrochloric acid, 1+1: Use redistilled acid and Pyrex glass 

vessels for preparation of solution.

Hydrochloric acid, Q.02N: Add 3.33 ml 1+1 hydrochloric acid 

to redistilled water and dilute to 1 liter. Store in Pyrex 

bottle.

Ammonium hydroxide, sp gr 0.9: Distill concentrated ammonia 

or absorb the tank gas in water. Keep in a polyethylene 

bottle.

Citric acid, 50 percent w/v: Dissolve 250 g citric acid (British 

Drug House grade or equivalent) in approximately 300 ml 

water and dilute to 500 ml.

PROCEDURE

1. Add a 1-g sample to only one of two 100-ml platinum dishes. 

In the steps that follow, reference is made only to the 

sample, but it is understood that what is done to the 

sample must be done to the blank. Add 10 to 15 ml
A-18 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALE!

hydrofluoric acid, 5 ml nitric acid, and 5 ml perchloric 

acid. Cover the dish with a platinum cover and digest 

on steam bath for 30 minutes. Remove cover and evaporate the solution on the steam bath to remove water.

2. Evaporate to fumes of perchloric acid, cover, and fume until 

organic matter is destroyed. Add 10 ml of water and 

evaporate to fumes of perchloric acid until about 1 ml 

remains. Cool. Add 2 ml 1 + 1 hydrochloric acid and 

15 ml water and digest to dissolve the salts. If a clear 

solution is obtained, transfer the solution to a separatory 

funnel and dilute to 25 ml. If, however, undecomposed 

sample is present, filter it off and wash with water, reserving the filtrate. Ignite residue at about 500°C and fuse 

with 0.5 g sodium carbonate. Dissolve the melt with a 

slight excess of hydrochloric acid and combine the solution 

with the reserved solution. Evaporate the combined 

solution to about 18 ml and either transfer to a separatory 

funnel with enough water to make the total volume 25 ml, 

when the heavy-metal concentrations are known to be 

low, or transfer the solution to a volumetric flask and 

dilute to volume.

3. Take either the entire solution or an aliquot, depending on 

metal concentrations, add 10 ml citric acid solution; if necessary, add more to keep the iron and aluminum in solution. 

Neutralize the solution with ammonium hydroxide to a pH 

of 9.0, using a pH meter. Carry out steps 3 and 4 as rapidly as possible, otherwise samples containing significant 

amounts of calcium and phosphate may give some precipitation of calcium phosphate that may occlude lead and 

cause low recoveries of this element.

4. Add 5 ml of 0.05 percent dithizone and shake for 2 minutes. 

Draw off the carbon tetrachloride phase into another separatory funnel. Add 5 ml more of dithizone to the aqueous 

phase and shake for 2 minutes. Draw off the carbon 

tetrachloride phase and combine with that reserved. Repeat these steps until the final dithizone-carbon tetrachloride layer is green. Reject the water layer. If more than 

five extractions are required, use a smaller aliquot and 

start over.

5. Wash the combined carbon tetrachloride extracts twice with 

5 ml of 1 + 99 ammonium hydroxide, reserving both the 

carbon tetrachloride and water layer. Add 2 ml dithizone 

to the water layer and shake. Draw off the dithizone layer 

and add it to the reserved carbon tetrachloride. It is important 

that the separated carbon tetrachloride be free of droplets of iron-containing solution.

6. Shake the combined carbon tetrachloride extracts for 2 minutes with 10ml of 0.02N hydrochloric acid. If the carbon 

tetrachloride remains red on shaking, add 1 to 2 ml of 0.05 

percent dithizone before finishing the shaking. Draw off 

the carbon tetrachloride into another separatory funnel 

and shake vigorously for 2 minutes with a fresh 10-ml 

portion of 0.022V hydrochloric acid. Combine the two 

acid extracts; add a few drops of carbon tetrachloride and 

draw off to remove any colored droplets of carbon tetrachloride, which are added to the reserved carbon tetrachloride solution. Transfer the aqueous layer to a 25-ml 

volumetric flask, add 0.43 ml 1 +1 hydrochloric acid, dilute 

to volume and mix. This solution is reserved for the 

determination of lead and zinc on separate aliquots of solution, as described on pages A-20 to A-22 The carbon tetrachloride layer contains the copper.

7. Evaporate the carbon tetrachloride containing the copper 

dithizonate to dryness in a 50- or 100-ml Pryex Erlenmeyer 

flask, add 0.5 ml nitric acid and 0.5 ml perchloric acid, 

and heat at 200° to 250°C until the solution is entirely 

colorless. Fume off all acid. Add 1 ml hydrochloric acid 

and 10 ml of water. Digest to dissolve the salts, cool and 

dilute to 50 ml with water in a volumetric flask. Reserve 

this solution for determination of copper by either the 

dithizone or cuproine methods described in the following

section.

COPPER

DITHIZONE METHOD

[Range in shale: 0.0003 to 0.010 percent copper] 

PRINCIPLES

The isolated copper in acid solution, obtained in step 

7 of the previous procedure, is evaporated to dryness to 

remove excess acid. The residue is redissolved in 

O.OOlAf hydrochloric acid, the volume of the solution is 

adjusted to 10 ml at a pH of 3, and the copper dithizonate is extracted into carbon tetrachloride for spectrophotometric determination by the mixed-color method 

(Sandell, 1937).

APPARATUS AND REAGENTS

Beckman DU spectrophotometer.

Dithizone: 0.002 percent w/v purified dithizone in purified carbon tetrachloride. Prepare daily from the 0.05 percent 

dithizone solution that is stable if stored in a refrigerator.

Water: Redistill from an all-Pyrex apparatus.

Hydrochloric acid: Redistill.

Hydrochloric acid, 0.0012V.

Standard copper stock solution, 1 ml = 0.5 mg copper: Dissolve 

0.2500 g of pure copper by warming with 5 ml nitric acid. 

Add 10 ml of hydrochloric acid and evaporate the solution to 

dryness. Add 4 ml hydrochloric acid and dilute to 500 ml 

with water in a volumetric flask.

Standard copper dilute solution, 1 ml = 2.5 micrograms copper: 

To a 5-ml aliquot of standard stock solution, add 20 ml hydrochloric acid and dilute to 1 liter in a volumetric flask.

PROCEDURE

1. Transfer a 5- or 10-ml aliquot of the solution containing the 

isolated copper (step 7, previous procedure) to a 50-ml 

beaker. Evaporate the aliquot, containing as much as 5 

micrograms copper, to dryness on a steam bath. Dry the 

residue in an oven at 120°C to expel all acid; cool the beaker, pipet 5 ml of 0.0012V hydrochloric acid, and warm briefly 

to dissolve the salts. Cool.

2. Transfer the solution to a dry separatory funnel. Rinse the 

beaker with 5 ml 0.0012V hydrochloric acid from pipet and 

add the solution to the funnel that now contains a total 

volume of 10 ml.

3. Pipet 10 ml 0.002 percent dithizone and shake the solution for 

2 minutes. The color of the solution should deviate from 

that of a pure copper ditbizonfte solution. (If the color of 

the carbon tetrachloride is red violet, too much copper is 

present, and a smaller aliquot of sample and blank solution 

should be taken in step 1.)
'CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-19

4. Draw off the carbon tetrachloride layer through a filter paper 

plug, rejecting the first 2 ml.

5. Determine the absorbance of the solution at 510 m/x, using 0.002 

percent dithizone as a reference solution.

6. Calculate the percentage of copper in the sample.

STANDARD CURVE

Take aliquots of standard copper solutions containing 

1, 2.5, and 5 micrograms of copper and follow steps 1 to 

5 of the procedure. It is important that the volumes of 

the aliquoted solutions be made to 10 ml for extraction 

with 10 ml dithizone, as the unknown solutions are 

extracted under these conditions.

ALTERNATIVE 2, 2' BIQUINOLINE METHOD

[Range in shale: 0.0003 to 0.010 percent copper] 

PRINCIPLES

The method is substantially that of Hoste and others 

(1953) with modifications according to Cheng and Bray 

(1953). The intensity of the copper biquinoline color 

is independent of pH within the range 2 to 9. The folio whig anibns and cations, in the ratio of 1,000 to 1 of 

copper, do not interfere with the determination: aluminum, arsenic, barium, calcium, cadmium, cobalt, iron, 

lithium, magnesium, molybdenum (VI), manganese, 

ammonium, nickel, antimony (III), tin (II), strontium, 

titanium, vanadium(V), tungsten(VI), zinc, acetate, 

borate, bromide, chloride, chlorate, perchlorate, tartrate, nitrate, sulfate, and phosphate. There may be 

interference from oxalate, cyanide, citrate, and 

rhodamide.

REAGENTS

Isoamyl alcohol: Distill from a Pyrex still and store the reagent 

in a dry Pyrex bottle.

Cuproine (2,2'biquinoline), 0.02 percent w/v in isoamyl alcohol: 

The solution obtained should be colorless. If the solution is 

yellow, the reagent is impure and should not be used.

Tartaric acid, 10 percent w/v.

Acetate buffer. Dissolve 8.2 g of sodium acetate and 5.8 ml acetic 

acid in water, and make to 200 ml in a volumetric flask.

Sodium hydroxide solution, 20 percent w/v. Store in polyethylene bottle.

Hydroxylamine hydro chloride, 15 percent w/v.

Standard copper solution. See Copper, dithizone method 

Cp. A-18).

PROCEDURE

1. Take a 10- or 20-ml aliquot from the reserved 50-ml solution 

containing the copper and transfer it to a separatory funnel. 

Adjust the volume to 20 ml with water, if a 10-ml aliquot is 

used. Alternatively, when only copper is to be determined 

and the dithizone separation has not been made, take a 20- 

ml aliquot of the acid sample solution at step 2 of the isolation procedure (p. A-18) and proceed with steps 2 to 6 below.

2. Add 1 ml tartaric acid, 1 ml of hydroxylamine hydrochloride, 

and then sodium hydroxide solution until a microdrop on a 

universal paper indicates a pH of 4 to 5.

3. Add 3 ml buffer solution; mix and let stand a few minutes.

4. Extract with a 20-ml portion of the cuproine solution for 2 

minutes (a smaller portion of solution is not sufficient for a 

5-cm cell). Let layers settle, insert a plug of filter paper in 

the stem of the funnel, and draw off the purplish isoamyl 

alcohol layer.

5. Measure the absorbance of the solution at 546 m/x against a 

blank prepared by taking 20 ml of water through steps 1 

to 5.

6. Calculate the percentage of copper in the sample.

STANDARD CURVE

Aliquot standard copper solutions containing 0, 5, 

20, and 50 micrograms of copper and dilute to 20 ml 

with water. Follow steps 1 through 5 of the procedure, 

using the blank solution for reference in the absorbance 

measurements.

PRECISION OF COPPER DETERMINATIONS

Copper was determined on the 80 samples in laboratory B with the dithizone method as described. The 

ranges of concentration for copper in the shale were 

from 0.0005 to 0.005 percent (57 samples) and from 

0.005 to 0.05 percent (23 samples). The results of 

replicates are given in table 20, those on the hidden 

splits in table 21, and those on the check samples in 

table 22. On the check samples, the results of B, A, 

and AI were obtained with the dithizone method. The 

results of A2 were determined with the dithizone separation method but were completed with the biquinoline method, and those of A3 were determined with 

biquinoline without prior dithizone separation. The 

results of A4 were obtained with the neocuproine (Smith 

and McCurdy, 1952) direct extraction of the copper 

without prior separation.

Graphical comparison of the data of B with those of 

A, AI, A? , A3 , and A4 is given on figure 7.
A-20 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALEl

COPPER, IN PARTS PER MILLION 

LABORATORY A

100 

COPPER, IN PARTS PER MILLION

LABORATORY A,

100

100

COPPER, IN PARTS PER MILLION 

LABORATORY A,

COPPER, IN PARTS PER MILLION 

LABORATORY A,

100

COPPER, IN PARTS PER MILLION 

LABORATORY A4

'FIGURE 7. Comparison of copper determinations of B with those of A, AI, A2 , As 

and At. Plots that coincide are indicated with the number involved.

TABLE 20. Replicate determinations l of copper, in percent, by 

laboratory B

[Analysis by dithizone method; Joseph Dinnin, analyst. Add 259500 to all sample 

numbers, except 00 to 05 to which add 259600, to form serial numbers]

41 . . ____. 0.0003 0.0005

54.... _ .0011 .0014

88... ............. .0011 .0015

60. .0018 .0020

65..... ...._ .0024 .0024

05. .0028 .0032

52. ... .0029 .0034

38. 0.0030 0.0030

78. _. _ .0036 .0038

58 _ __ .0063 .0066

56. .0070 .0087

63. ... .0070 .0078

95.. ... .0097 .010

i Precision and reliability of determinations:

Range

0.0005-0.005. 

.005- .05..

Standard Number of

deviations comparisons

0.00027 9

.00068 4

TABLE 21. Determinations 1 of copper, in percent, in hidden splits 

by laboratory B

[Analysis by dithizone method; Joseph Dinnin, analyst. Add 259500 to all sample 

numbers, except 00 to 05 to which add 259600, to form serial numbers. Groups indicate the samples that were duplicates]

33

97

49

96

99 

03

i

0.0036 

.0030

.0071 

.0072 

.0077 

.0090

53 

04.... ...... ......

65... ........

98 . ...... .

68 

01____

Precision and reliability of determinations:

Range 

0.0005-0.005..... _ .......

.005- .05

. 0.0049

nfien

0024

- .0024

. . 0039

nru.n

80

00

QO

m

OB

ni

O nriQo

.0084

 . .0080

0040

nnsn

Standard Number of 

deviations comparisons 

0. 00038 5 

.00080 8

TABLE 22. Determinations 1 of copper, in percent, in check samples 

[Add 259500 to each sample number to form serial number]

Sample

28.. -.

33 

37..... ...

39..- 

46..... 

48..- 

49- 

63. 

92 

94.-. 

B

0.0018 

.0036 

.0001 

.0025 

.0038 

.0038 

.0071 

.0074 

.0042 

.0034

A

0.0020 

.0028 

.0004 

.0026 

.0036 

.0041 

.0070 

.0070 

.0037 

.0026

AI

0.0018 

.0030 

.0004 

.0027 

.0039 

.0042 

.0071 

.0074 

.0038 

.0027

A2

0.0018 

.0035 

.0005 

.0028 

.0038 

.0036 

.0072 

.0071 

.0043 

.0024

A3

. 0. 0019 

.0027 

.0005 

.0026 

.0037 

.0037 

.0071 

.0064 

.0040 

.0025

A4

0.0024 

.0043 

.0008 

.0031 

.0042 

.0043 

.0072 

.0072 

.0043 

.0028

Mean

0.0020 

.0033 

.0005 

.0027 

.0038 

.0040 

.0071 

.0071 

.0041 

.0027

Difference (max 

min)

0.0006 

.0016 

.0007 

.0006 

.0006 

.0007 

.0002 

.0010 

.0006 

.0010

Standard deviation

0.00024 

.00063 

.00028 

.00024 

.00024 

.00028 

.00008 

.00040 

.00024 

.00040

i Precision and reliability of determinations:

B, 

B, 

B, 

B, 

B,

A ................... .

A,. ...... . ... _-

A2 ._ ... ... 

A3 

A4 ... ....... ... ....

Range

0. 0005 to 0. 005

Standard 

deviation

0.00034 

.00029 

.00014 

.00034 

.00040

Number of 

comparisons

8 

8 

8 

8 

8

0. 005 to 0. 05

Standard 

deviation

0.00020 

.00026 

.00016 

.00050 

.00011

Number of 

comparisons

2 

2 

2 

2 

2

Dithizone method; Joseph Dinnin, analyst.

Dithizone method; William Goss, analyst.

Dithizone method; William Goss and Irving Frost, analysts.

Alternative method, dithizone separation-biquinoline determination; William

Goss, analyst.

Biquinoline method, no prior dithizone separation; William Goss, analyst. 

Direct neocuproine method (Smith and McCurdy, 1952); Dwight Skinner,

analyst.

ZINC, DITHIZONE METHOD

[Range in shale: 0.001 to 0.040 percent zinc] 

PRINCIPLES

Zinc dithizonate is extracted with carbon tetrachloride from an acid solution at a pH of about 4.8 in 

in the presence of thiosulfate to inhibit coextraction of 

lead, copper, silver, gold, mercury, bismuth, and 

cadmium (Fischer and Leopoldi, 1937). The reaction 

of zinc ions with dithizone at a pH of 4.8 is slow and 

incomplete; the volumes of solutions and time for extraction must be rigorously controlled for both the 

standard and unknown solutions.

REAGENTS

Dithizone, 0.0025 percent (w/v), in pure carbon tetrachloride.

Acetate buffer: Add 16.4 g sodium acetate and 11.6 ml glacial 

acetic acid to water and dilute to 200 ml. Remove heavy 

metals by shaking the solution with 0.01 percent dithizone in 

carbon tetrachloride. Filter the solution through a small 

quantitative paper to remove droplets of carbon tetrachloride.

Sodium thiosulfate, 25 g of sodium thiosulfate pentahydrate in 

100 ml of water.

Standard stock solution of zinc, 1 ml = 0.5 mg zinc: Dry reagent 

grade zinc sulfate at 450°C. Weigh 0.2469 g of the anhydrous 

salt, dissolve it in 1 + 99 hydrochloric acid, make the solution to 

200 ml volume with 1 + 99 hydrochloric acid.

Standard dilute solution of zinc, 1 ml = 2.5 micrograms zinc: 

Dilute 5 ml of the stock solution with 1 + 99 hydrochloric acid 

to 1 liter in a volumetric flask.
CHEMICAL ANALYSES FOB SELECTED MINOR ELEMENTS IN PIEBBE SHALE A-21

PROCEDURE

1. Dilute 5 ml of the reserved acid extract solution containing 

the lead and zinc with water to 25 ml in a volumetric flask.

2. Transfer 5 ml of the diluted solution to a small beaker and 

evaporate the solution to remove acid. Pipet 5 ml of 0.02AT 

hydrochloric acid to the beaker and warm the solution 

briefly to dissolve the salts. Transfer the solution to a separatory funnel.

3. Rinse the beaker with 5 ml of water and transfer it to the 

separatory funnel.

4. Add 5 ml of buffer solution to the funnel and 1 ml of sodium 

thiosulfate solution.

5. Mix the solution and shake it vigorously for 3 minutes with 10 

ml of 0.0025 percent dithizone in carbon tetrachloride.

6. Draw off the carbon tetrachloride layer through a filterpaper plug, rejecting the first 2 ml.

7. Determine the absorbance of the filtered carbon tetrachloride 

solution at 530 m/* against 0.0025 percent dithizone in 

carbon tetrachloride as a reference solution.

8. Calculate the percentage of zinc in the sample.

STANDARD CURVE

Transfer aliquots of standard solution containing 0, 

2.5, 5, and 10 micrograms of zinc to small beakers and 

evaporate the solutions to dryness. Proceed with the 

method, steps 2 through 7, taking care to shake the 

standard solutions in the same manner (step 5) and for

ZINC, IN PARTS PER MILLION 

LABORATORY A

ZINC. IN PARTS PER MILLION 

LABORATORY A,

ZINC. IN PARTS PER MILLION 

LABORATORY A,

FIGURE 8. Comparison of zinc determinations of B with those of A, Ai, and A.I. 

Plots that coincide are indicated with the number involved;

the same length of time as was done with the unknown 

solutions.

PRECISION OF ZINC DETERMINATIONS

Zinc was determined on the 80 samples of shale in 

laboratory B by the dithizone method described. The 

ranges of concentration for zinc were from 0.0005 to 

0.005 percent (4 samples) and from 0.005 to 0.05 percent 

(76 samples). The results on replicate determinations 

of zinc by one chemist are given in table 23, those on 

hidden splits in table 24, and those on the check samples 

in table 25. On the check samples the results of B, A, 

and A2 were obtained with the dithizone method, whereas those of AI were obtained with the zincon method of 

Kader and others (1960).

Figure 8 shows the results of A, At , and A2 plotted 

against those of B.

TABLE 23. Replicate determinations l of zinc, in percent, by 

laboratory B

[Analysis by dithizone method; Joseph Dinnin, analyst. Add 259500 to each sample 

number to form serial number]

41... - _ 0.0040 0.0043

54... ._ .0083 .0090

60. . .0085 .0087

38. .011 .013

52....................... 0.011 0.014

65....................... .012 .012

78. __._ ... .013 .013

58.-. .___.... .025 .027

1 Precision and reliability of determinations in the range 0.005 to 0.05: standard 

deviation, 0.0010; number of comparisons, 8.

TABLE 24. Determinations * of zinc, in percent, in hidden splits 

by laboratory B

[Analysis by dithizone method; Joseph Dinnin, analyst. Add 259500 to all sample 

numbers, except 00 to 05 to which add 259600, to form serial numbers. Groups 

indicate the samples that were duplicates]

33. .. 0.018 

97 . __ ... .020

.012

.012

.012

.012

53 0.015

04. ___ .014

65. .012

.012

.016

.017 05.

0.011

.012

.038

.040

.013

.014

i Precision and reliability of determinations in the range 0.005 to 0.05: standard 

deviation, 0.00078; number of comparisons, 13.

TABLE 25. Determinations l of zinc, in percent, in check samples 

[Add 259500 to each sample number to form serial number]

Sample

28 

33 

37 

39 

dR

48 

49 

63 

92 

Oi

B

0.0060

.018

.0040

.014

.019

.033

.012

.0053

.018

.013

A

0.0054

.019

.0029

.013

.017

.028

.011

.0050

.016

.012

A,

0.0059

.018

.0029

1 .013

.018

.030

.0097

.0034

.016

.012

A,

0.0057

.016

.0022

.012

.016

.026

.010

.0042

.016

.012

Mean

0.0058

.018

.030

.013

.018

.029

.011

.0045

.017

.012

Difference (max 

min)

0.0006

.0003

.0018

.0020

.0030

.0070

.0093

.0019

.0020

.0010

Standard deviation

0.00029

.00015

.00088

.00097

.0015

.0034

.0045

.00092

.00097

.00049

i Precision and reliability of determinations in the range 0.005 to 0.05:

Standard Number of

deviation comparisons

B, A...... __._ __- 0.0014 10

B, Ai ... __ _ - .0011 10

B, As....... .0020 10

Alldata. .0013 60

B. Dithizone method; Joseph Dinnin, analyst.

A. Dithizone method; Irving Frost, analyst.

Ai. Modified zincon method; Claude Huffman and Howard Lipp, analysts.

AJ. Dithizone method; William Qoss, analyst.

592016 O 61-
A-22 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALE

LEAD, DITmzONE METHOD

[Range in shale: 0.0003 to 0.004 percent lead] 

PRINCIPLES

Lead is determined spectrophotometrically after extraction with dithizone in chloroform from an ammoniacal 

cyanide-citrate solution at a pH of slightly greater 

than 9. Cyanide prevents the reaction of zinc and 

small amounts of other metals.

REAGENTS

Sodium citrate, 10 percent w/v: Dissolve 10 g of trisodium 

citrate in 100 ml water and 0.5 ml ammonium hydroxide. 

Shake the solution with small portions of 0.01 percent dithizone in chloroform until the last portion is colored green. 

Reject the chloroform and store the solution in a polyethylene 

bottle.

Dithizone, 0.002 percent w/v, in chloroform: Prepared by dilution of a more concentrated dithizone solution in chloroform.

Potassium cyanide, 10 percent w/v: A milliliter of solution 

should impart no pink color to the chloroform phase when 

diluted with 2 ml of water and shaken with a milliliter or two 

of 0.002 percent dithizone. If necessary, potassium cyanide 

can be freed from lead as follows: Prepare an approximately 

saturated solution (50 g in 100 ml of solution) and shake 

with successive small portions of 0.01 percent dithizone in 

chloroform until a green color is obtained in the final extract. 

Extract the dithizone remaining in the aqueous layer with 

chloroform. Dilute the aqueous phase to 500 ml with water 

and store in polyethylene.

Hydrochloric acid, 1 + 99.

Ammonia-cyanide-citrate solution: Transfer 20 ml of 10 percent 

potassium cyanide solution and 5 ml of 10 percent sodium 

citrate solution to a 100-ml volumetric flask. Add a predetermined amount of pure concentrated ammonium hydroxide to the solution and dilute to 100 ml. The amount of 

ammonium hydroxide needed is such that when a 2-ml aliquot 

from the final volume of 100 ml is mixed with 10 ml of 1 + 99 

hydrochloric acid a pH of 9.4 to 9.6 (measured with a meter) 

will be obtained. Tests show that about 20 ml of concentrated ammonium hydroxide generally are required for the 

100 ml of mixed solution. Store the final solution in a polyethylene bottle.

Standard lead stock solution, 1 ml=0.5 mg lead: Dissolve 

0.1599 g of dried lead nitrate to make exactly 200 ml of solution in 1+99 hydrochloric acid.

Standard lead dilute solution, 1 ml=2.5 micrograms lead: 

Take 5 ml of stock solution and dilute to 1 liter with 1 + 99 

hydrochloric acid.

PROCEDURE

1. Transfer a 10-ml aliquot of the reserved acid extract solution 

containing the isolated lead and zinc to a 60-ml separatory 

funnel. If a smaller aliquot is used, add enough 1 + 99 

hydrochloric acid to make the total volume 10 ml.

2. Add 2 ml of the ammonia-cyanide-citrate solution.

3. Shake the solution with 10 ml of 0.002 percent dithizone in 

chloroform for 5 minutes. It is important to have equal 

volumes of solution and dithizone for this extraction.

4. Draw off the chloroform layer through a filter-paper plug, 

rejecting the first 2 ml of solution

5. Determine the absorbance of the filtered chloroform solution

at 520 m/u against 0.002 dithizone in chloroform as reference solution. 

6. Calculate the percentage of lead in the sample.

STANDARD CURVE

Transfer aliquots of standard solution containing 

0, 2.5, 5, and 12.5 micrograms of lead to separatory 

funnels. Pipet sufficient 1+-99 hydrochloric acid to 

make the total volume exactly 10 ml. Proceed with 

steps 2 to 5 of the procedure.

PRECISION OF LEAD DETERMINATIONS

Lead was determined on the 80 samples in laboratory B with the dithizone method described. The 

range of concentration for lead in all the 80 samples of 

shale was from 0.0005 to 0.005 percent. The results 

on replicate determinations are given in table 26, 

those on the hidden splits in table 27, and those on the 

check samples in table 28. Two gross errors are apparent in the data, one in table 27 and one in 

table 28.

Figure 9 compares the results for lead of A and 

A i with those of B.

50> 50

LEAD. IN PARTS PER MILLION 

LABORATORY A

50

LEAD, IN PARTS PER MILLION 

LABORATORY A,

FIGURE 9. Comparison of lead determinations of B with those of A and A i.

TABLE 26. Replicate determinations l of lead, in percent, by

laboratory B

[Analysis by dithizone method; Joseph Dinnin, analyst. Add 259500 to each sample 

number to form serial number]

61-....-.--. ------- 0.0018 0.0019

65.. - . .0024 .0024

78. .. . .0025 .0028

54 .0027 .0034

44. -- .0038 .0043

56 - .0038 .0039

58 .. 0.0012 0.0018

63. - .0013 .0015

71 .0014 .0014

60. .0015 .0018

38 .0018 .0018

50 ------------------- .0018 .0023

52. .0018 .0023

i Precision and reliability of determinations in the range 0.00005 to 0.005: standard 

deviation, 0.00026; number of comparisons, 13.

TABLE 27. Determinations l of lead, in percent, in hidden splits 

by laboratory B

[Analysis by the dithizone method; Joseph Dinnin, analyst. Add 259500 to all 

sample numbers, except 00 to 05 to which add 259600, to form the serial numbersGroups indicate the samples that were duplicates]

33.. 0.0013 

97. -- .0038

49- ._------- .0026

96_.__..-- .0027

99.. - -_ .0031

03-- .0030

« Precision and reliability of determinations in the range 0.0005 to 0.005: standard 

deviation, 0.00053; number of comparisons, 13.

53 

04

65 

98

68 

01 

 0.0013

... .0015

 .0024

 .0023

. .. .0024

 .0024

80 

00 

82. 

02 .- --

8f 

0.' 

----- 0.0023

 -- .0025

 .0029

 - .0033

 .0018

 -- .0023
'CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-23

TABLE 28. Determinations 1 of lead, in percent, in check samples 

[Add 259500 to each sample number to form serial number]

Sample

28..... . ...

33........... 

37--.. 

39-... ..- 

46-... 

48--. 

49... 

63... .... 

92... .. 

94--- . 

B

0.0015 

.0013 

.0032 

.0027 

.0029 

.0029 

.0026 

.0014 

.0023 

.0023

A

0.0018 

.0016 

.0032 

.0025 

.0026 

.0030 

.0051 

.0020 

.0028 

.0024

Ai

0.0016 

.0017 

.0027 

.0028 

.0026 

.0034 

.0030 

.0019 

.0024 

.0023

Mean

0.0016 

.0015 

.0030 

.0027 

.0027 

.0031 

.0036 

.0018 

.0025 

.0023

1 Precision and reliability of determinations in the range O.OOC 

5 

d 

B, A.... 

B, Ai 

Alldata . . .. .

Difference (max 

min)

0.0003 

.0004 

.0005 

.0003 

.0003 

.0005 

.0025 

.0006 

.0005 

.0001

Standard 

deviation

0.00018 

.00024 

.00030 

.00018 

.00018 

.00030 

.0015 

.00035 

.00030 

.00006

5 to 0.005: 

~"tandard Number of 

eviation comparisons 

0. 00060 10 

. 00026 10 

. 00047 30

B. Dithizone method; Joseph Dinnin, analyst. 

A. Dithizone method; Trving Frost, analyst. 

A:. Dithizone method; William Qoss, analyst.

ARSENIC

ACID DIGESTION, HETEROPOLY BLUE METHOD

[Range in shale: 0.0001 to 0.05 percent arsenic] 

PRINCIPLES

Arsenic is distilled as arsenious chloride after reduction with bromide and hydrazine sulfate, and is determined spectrophotometrically with the heteropoly blue 

method (Maechling and Flinn, 1930; Morris and Calvery, 1937; and Sandell, 1950, p. 178-183). The blue 

color is stable for at least 24 hours. Germanium distills with the arsenic but does not interfere. Antimony, 

tin, and mercury may also distill with the arsenic, unless 

the temperature of distillation is below 108°C. The 

distillation of selenium is largely prevented if sufficient 

hydrazine sulfate is used. Small amounts of selenium 

in the distillate do not interfere. Sample decomposition 

and solution is made with nitric, perchloric, and sulfuric acids. Tests show that arsenic is completely 

recovered from the shale and associated sediments by 

using this method. Hydrofluoric acid is avoided for 

sample decomposition, because of possible loss of arsenic 

as volatile fluorides and because subsequent attack on 

the glassware can introduce extraneous arsenic and 

silica.

APPARATUS AND REAGENTS

Beckman DU spectrophotometer supplied with 1- and 5-cm 

cells.

Pyrex glass still, 125-ml capacity: Erlenmeyer flasks with standard 19/38 taper outer joints, supplied with condenser and 

spray trap. The same flask is used for both digestion and 

distillation of the sample.

Hot plate equipped with motor drive for variable speed oscillation.

Acids, low in As (that is, about 1 microgram per 100 ml or less): 

Hydrochloric, nitric, sulfuric, and perchloric acids are required 

and should be tested for arsenic.

Sodium hydroxide, solution about IN.

Hydrazine sulfate.

Potassium bromide.

Glass beads.

Mixed reagent for color development:

Solution A. Dissolve 10 g ammonium molybdate, 

' (NH4 ) 6 Mo7(V4H2 O, in 139 ml sulfuric acid and dilute

to 1 liter. 

Solution B. Dissolve 0.75 g hydrazine sulfate in 500 ml

distilled water.

Solution C. Make this solution fresh as needed. Dilute 

50 ml solution A to approximately 450 ml with water, 

add 15 ml solution B, and make to 500-ml volume. 

Standard arsenic solution, 1 ml=l mg As: Dissolve 0.1320 g 

arsenous oxide (National Bureau of Standards standard 

sample 83a, As2 O3 ) in 5 ml 12V sodium hydroxide and make 

the solution slightly acid with hydrochloric acid. Dilute to 1 

liter.

Dilute standard arsenic solution, 1 ml = 10 micrograms As: 

Dilute 10 ml of standard stock solution to 100 ml.

PROCEDURE

1. Weigh 1.0 g of sample and transfer to a 125-ml Erlenmeyer 

flask with a 19/38 taper outer joint.

2. Add 10 ml nitric acid to the flask and place on steam bath for 

15 minutes.

3. Remove flask from the steam bath, cool, add 5 ml sulfuric 

acid, 7 ml perchloric acid, and several glass beads.

4. Place flask on the shaking hot plate and fume just until the 

first sign of sulfuric acid fumes. Cool.

5. Repeat steps 3 and 4 if organic matter is detected after the 

first treatment. Cool.

6. Rinse down the sides and neck of the flask with at least 25 ml 

water; place on the shaking hot plate and bring to incipient 

fuming again to remove residual nitric acid. Cool. 

7.Add 15 ml water to the flask and cool flask in pan of ice water; 

add 20 ml hydrochloric acid, 0.5 g potassium bromide, and 

1 g hydrazine sulfate.

8. Connect flask to the all-glass distilling apparatus. Collect 

the distillate in a 100-ml Erlenmeyer flask immersed in ice 

water and containing 10 ml cold water. Keep the delivery 

tip under water during the entire distillation. Experiments show that the solution starts to boil at 100°C and 

the temperature rises to 108°C as the hydrochloric acid 

distills over. This temperature must not be exceeded.

9. Continue the distillation only until 25 ml distillate is caught 

in the receiving flask or a total volume of 35 ml including 

the water added (usually about 30 to 35 minutes are 

required).

10. Add 10 ml concentrated nitric acid to the distillate and 

evaporate to dryness on a hot plate.

11. Place the flask in a drying oven at 130°C for one-half hour 

to volatilize traces of nitric acid left in the flask.

12. Add exactly 25 ml color reagent (solution C) to the flask.

13. Heat the covered flask on the steam bath for 20 minutes to 

develop the color. Cool.

14. When the solution is light blue (<50 micrograms As), transfer a portion to a 1-cm cell and complete the determination (steps 16 and 17).

15. When color of the soultion is dark blue (high in As), transfer 

the solution to a 200-ml volumetric flask with 0.5AT" sulfuric 

acid solution and dilute to volume with the Q.5N acid. No 

additional color reagent need be added, unless the arsenic 

content exceeds 400 micrograms.

16. Determine the absorbance of the solution at 840 mM , using 

1-cm cells. A reagent blank carried through the method 

is used as a reference.

17. Calculate the percentage of arsenic in the sample.
A-24 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALE

STANDARD CURVE

A blank and standards containing 5, 10, 20, 30 and 

40 micrograms of arsenic are carried through the procedure to establish a standard working curve for a 25-ml 

volume. A curve for 200 ml is similarly prepared from 

aliquots of standard solution containing 100, 200, 300 

and 400 micrograms arsenic.

ALTERNATIVE FUSION-HETEROPOLY BLUE METHOD

[Range in shale: 0.0001 to 0.05 percent arsenic] 

PRINCIPLES

The sample is decomposed by fusing with potassium 

carbonate-magnesium oxide mixture that destroys 

organic matter at the same time. Sodium carbonate 

cannot be substituted for potassium carbonate in the 

fusion mixture, because, in the distillation step, sodium 

chloride precipitates from the highly concentrated 

hydrochloric acid solution used. Although potassium 

chloride also tends to precipitate, this occurs only in 

the cold solution, because potassium chloride is soluble 

in the hot solution during the distillation. No provision is made to remove silica in this procedure; however 

silica remains in solution through most of the distillation, precipitating near the end.

APPARATUS AND REAGENTS

The appartus and reagents described in the previous 

method are required, except that a 200- or 250-ml 

distilling flask replaces the 125-ml flask used in the

other method.

PROCEDURE

1. Take a 0.25- to 0.5-g sample into a 30-ml platinum crucible 

and add 2 to 3.5 g of fusion mixture (3 parts potassium 

carbonate to 1 part magnesium oxide, by weight, intimately 

mixed). Mix the charge. Sprinkle 0.5 g of fusion mixture 

over the top as a cover. Place the crucible in a furnace at 

650°C and heat for 30 minutes. Gradually raise the temperature to 900°C and heat at 900°C for 30 minutes more 

or until organic matter is destroyed. Cool.

2. Place the crucible in a 200-ml tall-form beaker. Add 20 ml 

water, but do not add alcohol even if manganate is present. 

Place the beaker in a cold-water bath, cover, and add 

through the lip 60 ml concentrated hydrochloric acid, gently 

agitating the solution. Allow the melt to disintegrate in 

the cold. Remove the crucible and rinse it with 10 ml 

hydrochloric acid.

3. Transfer the solution to a 200-ml distillation flask and rinse 

the beaker with 10 ml hydrochloric acid (total volume 

solution, 100 ml). Add 2 ml hydrobromic acid and 0.5 g 

hydrazine sulfate crystals. Distill the solution into a tallform beaker containing 50 ml of cold water. The condenser 

tip should dip just into the water, and the beaker is gradually lowered as distillate is collected. During the distillation, the beaker should be kept in an ice bath. Collect 

50 ml of distillate.

4. Add 25 ml nitric acid to the distillate and evaporate the solution to dryness on a steam bath. Then heat the beaker in 

an oven at 130°C for 30 minutes to remove free nitric acid.

5. Add exactly 25 ml of mixed color reagent to the beaker. 

Cover and heat the solution for 20 minutes on the steam 

bath to develop color. Cool.

6. Determine the absorbance of the solution in a 1-cm cell at 

840 m/i, using a reagent blank carried through the method 

as a reference.

7. Calculate the percentage of arsenic in the samples.

PRECISION OF ARSENIC DETERMINATIONS

Arsenic was determined on the 80 samples of shale 

in laboratory A by using the acid decomposition method 

described. The ranges of concentration for arsenic 

were from 0.0001 to 0.0005 percent (10 samples), 0.0005 

to 0.005 percent (64 samples), and 0.005 to 0.05 percent 

(6 samples). The results on replicate determinations 

are given in table 29, those on the hidden splits in table 

30, and those on the check samples in table 31. Figure 

10 compares the determinations of A with B and of A 

with BI. The data show that all the arsenic is obtained 

by simple acid digestion of the shale.

ARSENIC, IN PARTS PER MILLION 

LABORATORY B

ARSENIC, IN PARTS PER MILLION 

LABORATORY B,

FIGURE 10. Comparison of arsenic determinations of A with those of B and Bi.

TABLE 29. Replicate determinations l of arsenic, in percent, by 

laboratory A

[Analysis by acid decomposition method; Claude Huffman, analyst. Add 259500 to 

all sample numbers, except 00 to 05 to which add 259600, to form serial numbers]

36_.

93

AO

55..

30..

46

11'recisio

0.000, 

.005

0.0003 

.0003 

.0004 

.0009 

.0009 

.0009

a and re 

HX005-

- .05..

0.0004 

.0005 

.0005 

.0009 

.0010 

.0010

liability

40 

05 

85 

78 

72 

68

- 0.0010

- .0012

- .0015

 .0016

- .0016

.nnis

of determinations: 

Range

0.0010 

.0012 

.0016 

.0016 

.0017 

.0018

88

?fi

56 

02 

91 

61

 0

Standard 

deviations 

0.00005 

.00010

0019 0.0020 

0037 . 0039 

0039 . 0039 

0044 .0044 

0053 .0053 

0098 .010

Number of 

comparisons

3 16

2

TABLE 30. Determinations l of arsenic, in percent, in hidden splits 

by laboratory A

[Analysis by acid decomposition method; Claude Huffman, analyst. Add 259500 to 

all sample numbers, except 00 to 05 to which add 259600, to form serial numbers. 

Groups indicate the samples that were duplicates]

QQ

97

49

CM

99 

03

1

................ 0.0014

 _ .0014

(\AQ

049

 .049

ACA

53 

65 

98 

 

68 

- 050 01 

Precision and reliability of determinations:

Range 

0.0005-0.005- 

.005 - .05.- - - 

. 0.0021

. .0022

. .0009

. .0009

- .0018

.0018

80 0.0013

00. . .... _ . __ .0013

82. _ ... - - .0044

02 .0044

86.- -. _ . _____ .0011

05 .0012

Standard Number of 

deviations comparisons 

0.000037 7

.00055 6
CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-25

TABLE 31. Determinations l of arsenic, in percent, in check samples 

[Add 259500 to each sample number to form serial number]

Sample

28- - 

33. 

37. 

39.-. 

46... 

48... 

49.-. 

63.-. -

92. 

94.. 

A

0.0006

.0014

.0002

.0006

.0010

.0032

.049

.0038

.0044

.0010

B

0.0005

.0013

.0002

.0007

.0009

.0032

.048

.0038

.0043

.0011

B,

0.0006 0.0003 0.0007

.0012

.0003 .0002

.0007 .0006 .0007

.0010

.0038

.048

Mean

0.0005

.0013

IWI9

.0007

.0010

.0034

.048

.0038

.0044

.0011

Difference (max 

min)

0.0004

0002

.0001

.0001

.0006

001

0

.0001

.0001

Standard deviation

0 00017

.00005

.00005

.00035

.0005

0

.00009

.00009

J Precision and reliability of determinations:

A, B .

All data... 

Range

0.0005 to 0.005

Standard 

deviation

0.00057 

.00013

Number of 

comparisons

9 

37

0.005 to 0.05

Standard 

deviation

0.00022 

.00057

Number of 

comparisons

1

3

A. Acid decomposition method; Claude Huffman, analyst. 

B. Acid decomposition method; Irving May and Frank Grimaldi, analysts. 

Bi. Alternative method, fusior decomposition; Irving May and Frank Grimaldi, 

analysts.

SELENIUM, DISTILLATION, VISUAL-ESTIMATION 

METHOD

[Range in shale: 0.0001 to 0.02 percent selenium] 

PRINCIPLES

Selenium is distilled as the tetrabromide from a 

sulfuric acid solution of the sample that has been freed 

of organic matter by oxidation with nitric acid in the 

presence of mercury as a catalyst (Robinson and others, 

1934; Mathews and others, 1937; Curl and Osborn, 

1938; and Wernimont and Hopkinson, 1940). Only 

germanium and arsenic accompany the selenium under 

the conditions outlined for the distillation. These 

elements do not interfere when selenium in the distillate is precipitated in the elemental form, with sulfur 

dioxide, from strong acid solutions (3 to 6N acid). 

The reduced selenium from the distillate is redissolved 

and reprecipitated in order to purify and concentrate 

it in a total volume of 2 ml of solution. The intensity 

of the color imparted to the solution by the suspension 

of elemental selenium is compared visually against 

known standards treated in the same manner. Selenium in amounts greater than 15 micrograms, noted at 

time of the first reduction, is redissolved in 10- or 25-ml 

volumes and aliquots taken for reduction and estimation of selenium. Volumetric or gravimetric procedures for completion of the selenium determination 

were not used for the shale because of the relatively 

low concentration of selenium in the samples.

APPARATUS AND REAGENTS

Pyrex glass stills, standard taper joints, 125- to 250-ml capacities, supplied with condensers.

Color comparison light source: An oblong box, 9 cm wide by 

19 cm long by 9 cm deep, with a slit for light passage, 0.1 by 

10 cm, positioned in the top face of the box directly over a 25 

watt tungsten filament tubular lamp, about 10 cm long, that 

is centered in the box by a socket mounted on one end of the 

box.

Vacuum pump and manifold, connected through a vapor trap 

to small bell-jar filter cells (Fisher Filtrators) equipped with 

filter sticks.

Fisher Filtrators, 7.5 by 12 cm, with an opening in the top for 

filter sticks and removable glass plate on the bottom.

Filter sticks, 3.5 by 1.2 cm with 9-cm stem length; medium to 

fine porosity.

Standard glass-fritted crucibles, about 20-ml size and medium 

porosity.

Tall-form flat-bottom glass vials with plastic screw crown: 

Capacities of 8 and 30 ml are preferable, but other tubes can 

be used.

A wire or metal rack designed to hold a series of vials partly 

immersed in a shallow pan containing water.

Sulfur dioxide: Compressed gas in cylinder with bleeder valve.

Sulfuric, nitric, red-fuming nitric, and 48 percent hydrobromic 

acids, all reagent grade.

Catalyst-acid: Five percent w/v mercuric oxide in concentrated 

nitric acid.

Bromine-hydrobromic acid mixture: Add 2 ml of bromine to 

100 ml of 9.2V hydrobromic acid.

Hydroxylamine hydrochloride, small crystals.

Standard selenium stock solution, 1 ml= 1 mg Se: Dry selenious 

acid in an oven to remove water and form selenium dioxide. 

Precautions must be taken because the material is hygroscopic. 

Weigh 0.2811 g of selenium dioxide, transfer to a 200-ml volumetric flask with about 50 ml water, add 25 ml 2 percent 

bromine-hydrobromic acid solution, and dissolve the compound without heating. Dilute to volume with water. 

Alternatively, dissolve 0.2000 g selenium metal in 25 ml bromine-hydrobromic acid solution, dilute to 200 ml with water, 

and standardize the solution gravimetrically.

Standard dilute selenium solution, 1 ml= 10 micrograms Se: 

Dilute 5 ml of stock solution to 500 ml with (2+ 1) hydrobromic acid. Make other dilutions as required, so that 

aliquots of reasonable size can be taken with normal precision.

PROCEDURE

1. Weigh 2.0-g sample and transfer to either a 125-ml Erlenmeyer flask or 150-ml beaker.

2. Add 5 ml nitric acid containing 5 percent mercuric oxide; 

cover the flask and keep it cool until any vigorous reaction 

subsides.

3. Add 5 ml nitric acid and 10 ml sulfuric acid, cover, and carefully digest on the hot plate until there is no danger of 

frothing over. Frothing may occur for samples high in 

organic matter.

4. Add increments of red-fuming nitric acid, 1 ml at a time, 

until organic matter is destroyed. This must be done 

cautiously with the flask covered and the solutions raised 

to the incipient fuming point of sulfuric acid after each 

addition of fuming nitric acid. When all organic matter is 

oxidized, rinse and remove the cover glasses and evaporate 

the solutions to incipient fumes of sulfuric acid. Cool. 

Repeat the rinsing and fuming to remove all nitric acid.
A-26 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALE

5. Cool the solution, and transfer the solution and sludge to the 

distilling flask. Rinse the flask with exactly 5 ml of water, 

adding the rinses to the still. This addition of water is 

necessary to prevent decomposition of hydrobromic acid 

by the sulfuric acid. Rinse the flasks three times with 5 

ml bromine-hydrobromic acid solution (total 15 ml) and 

pour the solution into the distilling flasks.

6. Connect the flask to the condenser at such an angle that insoluble sulfates go to one side on the bottom of the flask. 

Also place a receiver tube containing 2 to 3 ml water under 

the condenser with the tip of the condenser submerged 

and the tube supported in a beaker of ice water.

7. Start the distillation slowly with a small flame. Heat the 

the flask at a point above the sulfate sludge in order to 

minimize bumping. Controlled heating also can be done 

with an alcohol lamp. Glass beads or boiling tubes also 

will minimize bumping. The flame must be moved as 

the distillation proceeds, so that solution is over the flame at all 

times; otherwise, the flask may break. Distill over and 

collect about 18 to 20 ml of distillate. Stop the distillation 

when incipient fuming of sulfuric acid appears in the flask, 

indicating that all hydrobromic acid and water have distilled over.

8. Disconnect the distilling flask and rinse the condenser into 

the receiver tube with 2 to 3 ml of water. Arrange the 

tubes containing the distillates in a rack immersed in ice 

water. Pass a slow stream of sulfur dioxide to each solution, in turn, from a delivery tube placed just above the 

solution. Do not insert the delivery tube into the solution 

because of possible loss of selenium by sweeping out as the 

tetrabromide. Stir the distillates and continue gassing 

until the bromine is reduced to a colorless solution.

9. Add about 10 mg of hydroxylamine hydrochloride to each 

solution, stopper the tubes, and warm on the steam bath for 

20 minutes at 80°C. An estimate of the selenium content 

can be made at this time as a guide for the selection of the 

concentration range for the standards (step 11). Allow 

the solutions to stand overnight at room temperature. 

This is especially necessary if little or no selenium can be 

seen in the solutions.

10. Filter the solution with suction through a glass filter stick 

with medium or fine glass frit on a Fisher Filtrator and 

wash with water. Reject the filtrate if clear, otherwise 

refilter through the same frit.

11. The precipitate, if small, is redissolved by passing 1 ml 

bromine-hydrobromic acid solution through the frit of 

the filter stick, collecting the solution in a flat-bottomed 

vial placed inside the filtrator jar under the filter stick. 

Wash the frit with 1 ml of water to make the total volume 

2 ml of solution. At this time prepare a series of graded 

standards containing as much as 15 micrograms of selenium, each in a total volume of 2 ml of solution at the same 

acidity as the samples.

12. Gas the sample and standard solutions,, as before, with sulfur 

dioxide and add 1 to 2 crystals of hydroxylamine hydrochloride to each. Stopper and warm the vials for 20 

minutes at 80°C. Compare the color intensity of the 

sample against the standards by arranging the vials on 

the slit of light on top of the comparator box. The comparison can be made to advantage by estimating the intensity 

of color on the bottom of the meniscus of the solution or 

alternatively by looking down and across the vials at about 

a 60° angle to the vertical.

13. Calculate the percentage of selenium in the sample. Treat 

samples containing more than 15 micrograms of selenium

as in steps 11 through 13, except that selenium on the frit 

is dissolved and made to 10- or 25-ml volume with bromine-hydrobromic acid solution, the final volume depending on the selenium content. Take a 1-ml aliquot of this 

solution for the selenium determination.

PRECISION OF SELENIUM DETERMINATIONS

Selenium was determined on the 80 samples of shale 

in laboratory A by the method described. The ranges 

of concentration for selenium were <\0.0001 percent 

(12 samples), 0.0001 to 0.0005 percent (50 samples), 

0.0005 to 0.005 percent (13 samples) and 0.005 to 0.05 

percent (5 samples). The results on the replicate determinations are given in table 32, those on the hidden 

splits in table 33, and those on the check samples in 

table 34.

Figure 11 compares the determinations of A with 

those of B and BI graphically, but most of the check 

samples contained so little selenium that the comparison is of little value.

UJ n f

if) Cr 25

SELENIUM, IN PARTS PER MILLION 

LABORATORY B

SELENIUM, IN PARTS PER MILLION 

LABORATORY Bt

FIGURE 11. Comparison of selenium determinations of A with those of B and Bi. 

Plots that coincide are indicated with the number involved.

TABLE 32. Replicate determinations * of selenium, in percent, by 

laboratory A

[Analysis by method of this report; George Burrow, analyst. Add 259500 to all sample numbers, except 00 to 05 to which add 259600, to form serial numbers]

56. 0.0030 0.0040

62. . 0030 .0030

73. .0030 .0030 0.0040

04. .0030 .0040

49. .012 .012

96. . 012 .013

30. -. 0.0001 0.0001

35. .0001 .0001

40- .. .0001 .0001

45.- .. .0001 .0001

50-- - .0001 .0001

55.-. -- .0002 .0002

60. .-- .0002 .0002

65. .0002 .0002

94.- - .0002 .0003

71 . 0.0008 0.0010

91. .0010 .0010

82. .0012 .0016

95 . .0014 .0015

02- .0015 .0020

63. - .0024 .0025

27- - .0025 .0030

26. . .0030 .0030

53.. .0020 .0030

99. .012

03. . 012

61. .015

.013

.013

.016 .016

1 Precision and reliability of determinations:

Range

0.00005-0.0005. 

.0005 - .005.. 

.005 - .05...

Standard Number of 

deviations comparison*

 0.000023 9 

... .00032 15

 .00059 7

TABLE 33. Determinations l of selenium, in percent, in hidden 

splits, by laboratory A

[Analysis by method of this report; George Burrow, analyst. Add 259500 to all sample numbers, except 00 to 05 to which add 259600, to form serial numbers. Groups 

indicate the samples that were duplicates]

33

97

49

96

99

03

i Precision a

0.00005-0 .0005- 

.005 -

.... 0.0002

.... .0001

.... .012

 .013

 .013

013

53 _ ..........

65- 

98 .

68 .

01 - _ .

nd reliability of determinations:

Range 

.0005.. ....... ...................

. 006.. ...........................

.05 

0.0030 

.0040

.0002 

.0002

.0001 

.0001

80 

00

82 

02

86 

05

.... <0.0001

..... .0001

..... .0014

..... .0018

..... .0001

..... .0002

Standard Number of 

deviations comparisons 

0. 00012 5 

.00022 2 

.00060 6
CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-27

TABLE 34. Determinations 1 of selenium, in percent, in check 

samples

[Add 259500 to each sample number to form serial number]

Sample

28-...... . ___ .

33.-. .- .

37....... .. 

39... 

46............ ......

48.... 

49......... ......

63... .

92.......... ........

94...... .......

A

<0.0001 

.0002 

< .0001 

.0002 

.0002 

.0005 

.012 

.0025

.0002 

.0003

B

<0.0001 

.0001 

< .0001 

.0001 

.0001 

0008 

.010

.0002 

.0001

Bi

<0.0001 

.0001 

< .0001 

.0001 

.0001 

.0005 

.012 

.0022 

.0001 

.0002

Mean

<0.0001 

.0001 

< .0001 

.0001 

.0001 

.0006 

.011 

.0024 

.0002 

.0002

Difference 

(max 

 min)

0.0001

.0001 

.0001 

.0003 

.0020 

.0003 

.0001 

.0002

Standard 

deviation

0.00006

.00006 

.00006 

.00018 

.0012 

.00018 

.00006 

.00012

1 Precision and reliability of determinations:

A, B___ ..

A, B, ......

Range

0. 00005 to 0. 0005

Standard 

deviation

0.00026 

.00003

Number 

of comparisons

7 

7

0. 0005 to 0. 005

Standard 

deviation

0.00020 

.00016

Number 

of comparisons

2 

2

0. 005 to 0. 05

Standard 

deviation

0.0021

Number 

of comparisons

1

A. Nitric and sulfuric acid digestion, method of this report; George Burrow, analyst.

B. Nitric and perchloric acid digestion; Mary Fletcher, analyst.

Bi. Digestion and distillation as in B, but distillate evaporated with nitric acid before 

reduction of selenium and development of selenium color; Mary Fletcher, analyst.

MOLYBDENUM AND TUNGSTEN

ISOI^ATION BY METHOD 1, ALPHA-BENZOINOXIME 

PRECIPITATION

[Range in shale: 0.0001 to 0.04 percent molybdenum. Tungsten method was designed for similar range, but tungsten was not found in the samples]

PRINCIPLES

Molybdenum and tungsten are isolated simultaneously from a solution of the sample in hydrochloric 

acid by precipitation with alpha-benzoinoxime, using 

vanadium as a collector. This separation (Knowles, 

1932) is used because of its specificity, completeness, 

and rapidity. Only palladium, niobium, tantalum, 

chromium, and vandium also precipitate, and they do 

not interfere with the determination of molybdenum 

and tungsten under the conditions specified. Molybdenum is determined spectrophotometrically as the 

thyocyanate after reduction with stannous chloride 

(Hurd and Alien, 1935; Sandell, 1950, p. 455-459). 

Ethyl acetate is substituted for isoamyl alcohol as the 

solvent for the extraction, and tartaric acid is used to 

hold the tungsten in solution. At least 100 micrograms of tungsten can be tolerated during the extraction 

of the molybdenum under the conditions specified. 

Also at least 50 micrograms of molybdenum can be 

tolerated without effect on the tungsten determination 

under the conditions specified. Consequently, there is 

no interference either by tungsten in the molybdenum 

determination or by molybdenum in the tungsten determination in the analysis of shale, silicate rocks, and

other materials containing trace amounts of these two 

elements.

Tungsten in the aqueous phase, after the separation 

of molybdenum, is reduced with titanous sulfate after 

making the solution strongly acid (about 44 percent 

v/v). The tungsten-dithiol complex is then formed 

and extracted into chloroform for spectrophotometric 

determination. This modification of the dithiol-tungsten method, using titanous sulfate as the reductant, 

is that of Claude Huffman (written communication, 

1956) and differs in several respects from dithioltungsten methods (Miller, 1944; Short, 1951; Greenberg, 1957) and other methods dealing primarily with 

alloys.

APPARATUS AND REAGENTS

Beckman DU spectrophotometer supplied with both 1- and 

2-cm cells.

Shaking hot plate.

Potassium thiocyanate, 10 percent w/v solution, in water.

Stannous chloride, 10 percent w/v solution, in about 1.5AT 

hydrochloric acid: Dissolve 12.6 g tinfoil in 42 ml concentrated 

hydrochloric acid in a platinum dish. The platinum dish 

acts as a catalyst to dissolve the tin. Dilute the solution 

to 200 ml in a volumetric flask and add a small piece of 

metallic tin to minimize oxidation.

Ferrous ammonium sulfate, 1 percent w/v solution of Fe (NHOz- 

(SO4) 2 -6H20, in 0.2N sulfuric acid.

Standard molybdenum solution, 1 ml =100 micrograms Mo: 

Dissolve 0.1840 g of ammonium molybdate, (NHOeMorO^- 

4H2O, in water and dilute to 1 liter.

Ethyl acetate: Reagent grade, anhydrous.

Alpha-benzoinoxime solution: Dissolve 8 g alpha-benzoinoxime 

in 100 ml of concentrated acetic acid by warming the solution 

on the steam bath.

Chloroform: Reagent grade.

Dithiol (4 methyl, 1, 2 dimercaptobenzene), 0.2 percent w/v 

solution, in 1 percent w/v sodium hydroxide: The solution 

should be made fresh at least every 2 weeks because of air 

oxidation of the reagent.

Standard tungsten solution, 1 ml =100 micrograms W: Dissolve 

0.1794 g sodium tungstate dihydrate in water and dilute 

to 1 liter.

Titanous sulfate solution: Mix 2 g of reagent-grade titanium 

dioxide with 4.5 g of ammonium sulfate. Add 12.5 ml of 

concentrated sulfuric acid. Heat cautiously over a burner, 

in a well-ventilated hood, until foaming stops. Increase the 

heat to boiling temperature and swirl the boiling liquid 

vigorously over the full flame until all the titanium dioxide 

dissolves. Cool. Add carefully, while swirling, enough cold 

distilled water to dilute the solution to about 50 ml. Decant 

or filter the solution immediately, to avoid hydrolysis, into 

a flask containing zinc amalgam, prepared by adding 0.8 g of 

granular zinc metal to 0.6 ml of mercury and 0.5 ml of 5 

percent sulfuric acid. Stopper loosely and swirl the solution 

occasionally until the evolution of gas stops, and then stopper 

the flask tightly. This solution is kept at full reducing 

strength by storing with the zinc amalgam in the tightly 

stoppered flask.

Vanadium solution, 1 ml = 500 micrograms V: Dissolve 0.2296 g 

ammonium metavanadate (NH4VOs) in water and dilute to 

200 ml with water in a volumetric flask.
A-28 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALE

PROCEDURE 

ISOLATION OF MOLYBDENUM AND TUNGSTEN

1. Weigh 1.0-g sample, and transfer to a platinum dish.

2. Add 10 ml concentrated nitric acid, 10 ml perchloric aeid, 

and about 10 ml hydrofluoric acid to the dish. Place the 

solution on a steam bath and evaporate the water. Transfer 

the dish to a hot plate and fume the solution to near dryness. 

Add 10 ml water and repeat step 2, omitting the nitric acid. 

Cool.

3. Add 40 ml distilled water and 5 ml concentrated hydrochloric 

acid to the dish, cover, and heat on steam bath for 15 

minutes. Transfer the solution to a 500-ml Erlenmeyer 

flask and dilute to 100 mi-volume with water.

4. Chill the solution by placing the flask in a pan of ice water. 

Add about eight drops bromine water to oxidize molybdenum and tungsten. Add 1 ml vanadium solution and 

5 rrl alpha-benzoinoxirne solution and stir the solution 

thoroughly.

5. Allow the solution to stand 20 minutes for complete precipitation; filter off the precipitate, using » medium-porosity 

filter paper. Wash the flask and precipitate three times 

with a 1 percent hydrochloric acid solution containing 1 

percent alpha-benzdinoyime (w/v).

6. Return the precipitate and filter paper to the same 500-ml 

Erlenmeyer flask.

7. Add 25 ml water, 10 ml nitric acid, 10 ml perchloric acid, and 

5 ml sulfuric acid to the flask and place on shaking hot plate. 

Fume the solution to near dryness. Cool.

8. Cautiously add 5 ml ammonium hydroxide to the flask and 

agitate to redissolve any tungsten that may have precipitated at step 7.

9. Add 20 ml distilled water, 12.5 ml concentrated hydrochloric 

acid, and 1 g tartaric acid to the flask and heat on steam 

bath for 15 minutes. Cool.

10. Transfer the solution to a 50-ml volumetric flask and dilute 

to volume with water.

DETERMINATION OF MOLYBDENUM

1. Transfer a 15-ml aliquot of the solution to a 60-ml separatory 

funnel. Add a few crystals of tartaric acid to each solution and allow to dissolve. Add five drops ferrous ammonium sulfate solution, 1 ml 10 percent potassium thiocyanate 

solution, and 1 ml 10 percent stannous chloride solution; 

stopper the funnel and shake thoroughly.

2. Add exactly 10 ml ethyl acetate to the separatory funnel and 

shake vigorously for 30 seconds. Allow the two layers to 

separate, and draw off the water-acid layer into a clean 

150-ml beaker.

3. Add 5 ml of 15 percent hydrocholoric acid to the separatory 

funnel to rinse the stem and draw off the acid solution into 

the same 150-ml beaker used in step 2. Reserve this solution for the tungsten determination.

4. Pour the ethyl acetate layer out the top of the separatory 

funnel into a 25-ml glass-stoppered Erlenmeyer flask. 

Transfer a portion of the solution to a 1-cm cell and determine its absorbance at 470 ran against the reagent blank 

as reference.

5. Calculate the percentage of molybdenum in the sample.

STANDARD CURVE

Blanks and standards containing 5, 10, 20, and 40 

micrograms of molybdenum are carried through steps 

1 to 4 of the procedure to establish a standard working 

curve.

DETERMINATION OF TUNGSTEN

1. Add 12 ml concentrated hydrochloric acid to the solution 

- reserved for the tungsten determination at step 3 of the 

molybdenum determination.

2. Add dropwise about 1 ml titanous sulfate solution, until a 

purple color persists and the tungsten is reduced.

3. Add 2 ml dithiol solution, stir, and heat the solution on a 

steam bath for 20 minutes. Cool.

4. Transfer the solution to a 125-ml separatory funnel.

5. Rinse the beaker with exactly 10 ml of chloroform and transfer it to the separatory funnel. Shake the separatory 

funnel for 1 minute to extract the tungsten-dithiol complex.

6. Draw off the chloroform layer into a 25-ml Erlenmeyer flask 

fitted with a glass stopper. Transfer portions of the solution to a 2-cm cell and determine the absorbance of the 

solution at 640 mp, using a reagent blank as a reference.

7. Calculate percentage of tungsten in sample.

STANDARD CURVE

A blank and standards containing 5, 10, 15, and 20 

micrograms of tungsten are carried through steps 1 to 

6 of the procedure to establish a standard curve.

ISOLATION BY ALTERNATIVE METHOD 2, ALPHABENZOINOXIME EXTRACTION

[Range in shale: same as for method 1] 

PRINCIPLES

Tungsten (and molybdenum) in 0.1 to l.SN hydrochloric acid is concentrated by extraction of the alphabenzoinoxime complexes with chloroform (Jeffery, 1956; 

Goldstein and others, 1958). Chromium(VI) and 

vanadium(V), which according to to Knowles (1932) 

also form insoluble precipitates with alpha-benzoinoxime, are not extracted under the conditions specified. 

Aluminum, iron, titanium, fluorine, and phosphate are 

not extracted nor do they interfere with the extraction 

of molybdenum and tungsten. The tungsten (or molybdenum) is then determined colorimetrically with thiocyanate in the presence of a reducing agent. Tungsten 

does not interfere in the thiocyanate method for the 

determination of molybdenum with potassium iodide 

and sodium sulfite as reducing agents (Hope, 1957). 

In 6 to 8N hydrochloric acid, molybdenum interference 

is negligible in the thiocyanate method for the determination of tungsten with stannous chloride as the reducing 

agent; the intensity of the color given by molybdenum 

is about one-fiftieth to one-hundredth as strong as that 

given by an equal weight of tungsten (Sandell, 1950, 

p. 584). Although some analysts carry out the tungsten-thiocyanate reaction in at least SN hydrochloric 

acid, the method of Gran (1951) with 5N hydrochloric 

acid is used in the following procedure.

APPARATUS AND REAGENTS

Beckman DU spectrophotometer supplied with 5-cm cells.

Potassium thiocyanate solution, 25 percent w/v.

Stannous chloride solution, 10 percent w/v of the dihydrate in 

concentrated hydrochloric acid: The crystals are warmed 

with hydrochloric acid until a clear solution is obtained.
(CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-29

Sodium hydroxide, 1.5AT: Dissolve 6.0 g of sodium hydroxide

in water and dilute to 100 ml. 

Alpha-benzoinoxime solution: Dissolve 2 g of reagent in 100 ml

alcohol. 

Standard tungsten stock solution, 1 ml 1 mg W: Dissolve

0.3588 g sodium tungstate dihydrate in water and dilute to

200 ml with water. 

Standard tungsten dilute solution, 1 ml 10 micrograms W:

Dilute 5 ml of stock solution with water to 500 ml. 

Chloroform. 

Fusion mixture: Mix intimately 10 parts potassium carbonate

with 1 part ground potassium nitrate by weight.

PROCEDURE

1. Take a 2-g sample in a platinum crucible. Ignite to destroy 

organic matter «500°C if molybdenum is also to be determined; 700°C or less if only tungsten is to be determined).

2. Add 10 g of fusion mixture to the sample, mix, and cover with 

0.5 to 1 g more of flux. Cover with platinum lid and heat 

for 15 minutes at 650° C.

3. Gradually increase the heat until a quiet, clear melt is obtained 

and continue heating at this temperature for at least 5 

minutes more. Cool.

4. Transfer the crucible to a beaker. Add 100 ml of water and 

several drops of alcohol (more if required to reduce manganate), and heat to boiling, breaking all lumps. Remove 

crucible, rub with a policeman, and rinse, adding rinses to 

beaker. Digest the solution on steam bath until the precipitate is filterable. Filter, collecting filtrate in a beaker 

or casserole, and wash thoroughly with hot 0.1 percent 

potassium carbonate solution. Discard residue.

5. Carefully neutralize the filtrate with 1+1 hydrochloric acid 

until methyl orange is red and then add 20 ml more of 

the 1 + 1 acid.

6. Evaporate the solution to dryness to dehydrate the silica. 

Add 20 ml 1 + 1 hydrochloric acid, cover, and digest the 

solution on a steam bath. Add 20 ml of water and digest 

the solution to dissolve soluble salts.

7. Filter the solution on a fast paper and wash with water. Reserve filtrate.

8. Ignite residue in a platinum crucible. Cool and moisten with 

water. Add 10 to 15 ml hydrofluoric acid and five drops 

sulfuric acid and evaporate on a steam bath to volatilize 

silica and water. Bring to fumes of sulfuric acid and heat 

until all sulfuric acid is removed. Ignite at 400°C. Cool.

9. Add a very small amount of potassium carbonate to the 

crucible and fuse (even if no residue is present), allowing 

the melt to play over all surfaces of the crucible. Cool. 

Add 5 ml of water and a drop of methyl orange indicator. 

Cover and carefully add 1 + 1 hydrochloric acid through a 

small opening until methyl orange turns red and then add 

a drop or two of the 1 + 1 acid in excess. Combine with 

the reserved main solution.

10. Transfer the solution to a separatory funnel and dilute with 

water to about 95 ml. Add 3 ml alpha-benzoinoxime 

solution and shake well. Add 10 ml chloroform, and 

shake for 2 minutes to extract the molybdenum and 

tungsten into the organic phase.

11. Allow the two phases to separate, and carefully withdraw 

the lower organic layer into a 50-ml flask. Repeat the 

extraction three more times with 7-ml portions of chloroform, combining all chloroform extracts.

12. Evaporate the chloroform by gentle heating. Add 2 ml 

nitric acid and digest the solution. Add 0.5 ml perchloric 

acid to the flask and take to fumes to destroy organic

matter completely. Heat at 200°C on sand bath to 

remove perchloric acid (including any condensate in 

the neck of the flask).

13. Add 5 ml 1+1 hydrochloric acid to the flask and evaporate 

the solution to dryness. Add 1 drop 1 + 1 hydrochloric 

acid and 5 ml water to the flask, cover, and digest. Pipet 

2 ml 1.5N sodium hydroxide, cover, and digest. Cool 

the solution. If niobium has carried through the method, 

it will drop out of solution in dilute sodium hydroxide 

and can be filtered off on a very small filter and then 

washed with 2 ml of water.

14. If both molybdenum and tungsten are to be determined, 

transfer the solution to a 25-ml volumetric flask, adjust 

to volume, and mix the solution. Transfer an aliquot 

of solution to a 50-ml volumetric flask, and complete 

the determination of molybdenum according to the 

alternative method 3, starting at step 12 (p. A-30). A 10-ml 

aliquot can be used for the tungsten determination, steps 

15 through 17, below. If only tungsten is to be determined, transfer the solution (step 13, alternative method 2) 

to the 25-ml volumetric flask and wash to give a total 

volume not exceeding 12 ml. Complete the determination 

of tungsten following steps 15 through 17 below.

15. Add 1 ml potassium thiocyanate solution to the flask containing the tungsten, and pipet 10 ml of stannous chloride 

in concentrated hydrochloric acid solution and mix. 

Exactly 60 minutes after the addition of the tin 

solution, dilute the solution to the mark with distilled 

water and mix.

16. Determine the absorbance of the solution at 395 m/i in 

5-cm cells against a blank solution as reference. To 

prepare the blank solution, pipet 10 ml water, 1 drop 

1 + 1 hydrochloric acid, and 2 ml sodium hydroxide into 

a flask and continue with step 15.

17. Calculate the percentage of tungsten in the samples. A 

blank should be carried throughout the procedure.

STANDARD CURVE

Standards arid a blank solution should be prepared 

along with the samples at step 15 so that a standard 

curve can be made with each set of samples.

Pipet 0, 5, 10, 20, and 50 micrograms tungsten 

standard dilute solution into dry 25-ml volumetric 

flasks. Add by pipet sufficient water to make 10 ml 

of solution, 1 drop 1 + 1 hydrochloric acid, and 2 ml 

sodium hydroxide and proceed according to step 15 

of the procedure.

ISOLATION OF MOLYBDENUM BY ALTERNATIVE METHOD 

3, CUPFERRON SEPARATION

[Range in shale: 0.0001 to 0.04 percent molybdenum] 

PRINCIPLES

Molybdenum is concentrated by cupferron precipitation in the presence of iron as a carrier. Iron is 

separated by sodium hydroxide fusion and leaching; 

molybdenum is determined in the filtrate spectrophotometrically.

This spectrophotometric method is a variation of 

the thiocyanate method, using potassium iodide and 

sodium sulfite as reducing agents in the presence of 

a trace of copper to increase rate of color development
A-30 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALEl

without altering the final intensity (Hope, 1957). At 

least 7 mg of tungsten and 10 mg of iron can be present 

in the final 50-ml volume without interference. The 

addition of 5 ml of 30 percent w/v ammonium citrate 

will allow as much as 50 mg of tungsten to be present 

without interference. Bismuth and vanadium complexes do not absorb at 460 m/x. Antimony does not 

interfere. Sulfuric acid concentrations greater than 

0.3N in the final solution reduce the rate of color 

development. At least 1.5 g of sodium salts do not 

interfere.

APPARATUS AND REAGENTS

Beckman DU spectrophotometer supplied with 1- and 5-cm cells. 

Ammonium molybdate standard stock solution, 1 ml= 1 mg Mo:

Dissolve 0.3680 g ammonium molybdate, (NH4 ) 6 Mo7O24 4H2O,

in water and dilute to 200 ml in a volumetric flask. 

Standard molybdenum dilute solution, 1 ml = 10 micrograms Mo:

Dilute 5 ml of standard stock solution to 500 ml in a volumetric

flask.

Hydrochloric acid, 1+1.

Ammonium thiocyanate solution, 25 percent (w/v). 

Potassium iodide, 50 percent (w/v). 

Sodium sulfite, 1 percent (w/v). 

Copper chloride solution, 0.1M: Dissolve 1.7 g cupric chloride

dihydrate in water containing 1 ml hydrochloric acid and

dilute to 100 ml. 

Cupferron solution, 6 percent (w/v) aqueous: Prepare as needed

and keep the solution cold.

PROCEDURE

1. Weigh a 2-g sarrple and transfer it to a platinum dish. Place 

the dish in a regulated muffle at 450°C to destroy as much 

organic matter as possible by ignition. At 500°C molybdenum trioxide begins to sublime.

2. Moisten the sample with water, add 20 ml hydrofluoric acid, 

5 ml nitric acid, and 10 ml perchloric acid to the dish. 

Cover and digest 30 minutes on a steam bath. Take the 

solution to fumes of perchloric acid. Add 10 ml of water 

and evaporate to fumes again. Repeat.

3. Add 20 ml hydrochloric acid and 30 ml water to the dish. Digest 

to dissolve soluble salts. A clear solution should be 

obtained. Transfer the solution to a 400-ml beaker, and 

add water to a volume of about 230 ml.

4. Cool the solution in an ice bath. Add 70 ml of cold cupferron 

solution (more if required to precipitate all the iron); stir 

in paper pulp and filter the solution when the precipitate 

is fully clotted (in a few minutes).

5. Wash the precipitate with a cold solution containing 40 ml 

hydrochloric acid and 15 ml cupferron to 500 ml of solution. 

Reject filtrate.

6. Squeeze out as much water as possible by placing hand over 

funnel and pressing down until no more fluid is forced out.

7. Transfer the precipitate and paper to a silver crucible and 

dry overnight in an oven at 50°C.

8. Ignite the paper at low heat, very gradually raising the 

temperature to 500° C, but no higher, until all carbon is 

removed.

9. Add 2 g sodium hydroxide and fuse the residue. Leach the 

melt with boiling water .

10. Filter the solution into a platinum dish and wash the paper 

with 0.1 percent sodium hydroxide solution. Reject 

residue.

11. Concentrate the solution to less than 25 ml and transfer to 

a 25-ml volumetric flask. Dilute to volume and mix.

12. Transfer a 15-ml aliquot to a 50-ml volumetric flask. Add 

20 ml 1 +1 hydrochloric acid all at once. Swirl the flask 

for several minutes to remove the carbon dioxide from 

the solution.

13. Add the following solutions to the flask: 1 drop of copper 

chloride solution, 3 ml ammonium thiocyanate, 3 ml potassium iodide, and 2 ml sodium sulfite.

14. Dilute to volume, mix, and allow the solution to stand for 30 

minutes.

15. Obtain the absorbance in 1- or 5-cm cells at 460 m/* (slit 

about 0.03 mm), using a blank as reference. Prepare 

the reference solution at the same time by following 

steps 12 to 15 and by using 15 ml of water containing 1.2 

g of sodium hydroxide instead of sample solution at step 

12.

16. Calculate the percentage of molybdenum in the sample. 

Carry a reagent blank through the complete procedure; 

use about 25 mg Fe2O3 (nitrate salt) so that a precipitate 

is obtained in the cupferron step.

STANDARD CURVE

Transfer 2, 5, 10, and 20 micrograms of molybdenum 

standard solution to 50-ml flasks and include a reagent 

blank; add 1.2 g of sodium hydroxide and water to 

15 ml. After dissolution follow steps 12 to 15 of the 

procedure. Determine the absorbance with the blank 

solution as reference.

PRECISION OF TUNGSTEN DETERMINATIONS

Tungsten was assigned to laboratory A for the analysis of the 80 samples of shale. The concentration of 

tungsten was found to be less than 1 ppm, using method 

1, for the first 48 samples of the set of 80. Because the 

samples analyzed represented all the different types of 

material and many of the different sample locations, 

the remaining 32 samples were not analyzed for tungsten. A further check for tungsten was made by 

method 1, using a 5-g portion of sample 259526. This 

test showed less than 0.00003 percent tungsten. Although no supporting data were obtained for the precision of either the method or alternative method for 

the determination of tungsten in shale, the methods 

are included for future use if needed.

PRECISION OF MOLYBDENUM DETERMINATIONS

Molybdenum was determined on the 80 samples of 

shale in laboratory A by method 1, described for the 

determination of molybdenum and tungsten. The 

ranges of concentration for molybdenum were less 

than 0.0001 percent (27 samples); 0.0001 to 0.0005 

percent (33 samples); 0.0005 to 0.005 percent (14 samples), and 0.005 to 0.05 percent (6 samples).
CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-31

The results on replicate determinations are given in 

table 35, those on the hidden splits in table 36, and 

those on the check samples in table 37. The results 

of A are compared graphically with those of B in figure 

12.

MOLYBDENUM, IN PARTS 

PER MILLION 

LABORATORY B

FIGURE 12. Comparison of molybdenum determinations of A with those of B. 

that coincide are indicated with the number involved.

Plots

TABLE 35. Replicate determinations l of molybdenum, in percent, 

by laboratory A

[ Analysis by alpha-benzoinoxime precipitation, method 1; Dorothy Ferguson and 

Claude Huffman, analysts. Add 259500 to all sample numbers, except 00 to 05 to 

which add 259600, to form serial numbers]

58 <0.0001 <0

81 < .0001 < .

93 < .0001 < .

98 < .0001 < .

53 < .0001

68 < .0001

28 .0001

38. .0001

43 .0001

0001

0001

0001

0001

0001

0001

0001

0001

0001

78 

33 

41

45- 

83 

88 

48 

56 

26 

0.0001

.0001

.0001

.0001

.0005

.0007

.0009

.0010

.0012

0. 0001

.0002

.0003

.0002

.0005

.0009

.0009

.0011

.0013

63-

61.

73-

27-

91-

82-

99-

03-

49.

0.0016 0.0017

.0022

.0028

.0039

.0048

.0058

.032

.032

.035

0022

0028

0046

0048

0058

036

033

035

0. 0020

.035

1 Precision and reliability of determinations:

0.0005-0.005

. 005- 05 

Range

Standard

deviations

0 00018

.'0016

Number of

comparisons

12

fi

TABLE 36. Determinations l of molybdenum, in percent, in 

hidden splits by laboratory A

[Analysis by alpha-benzoinoxime precipitation, method 1; Dorothy Ferguson and 

Claude Huffman, analysts. Add 259500 to all sample numbers, except 00 to 05 to 

which add 259600, to form serial numbers. Groups indicate the samples that were

33............... 0.0002

97. ........... <0001

49. .......... .035

% AQQ

99...... ......... .034 

03.... ........... .033

« Precision and reliability 

viation, 0.00095; number of

53- ..

04 

65- .. ..

68 .... .

01.. __ . ...

. 0. 0001

iwn

<0001

- <.0001 

0001

_ <nnoi

QA

00

82 

02 

Sfi

ns

 - <0.0001

 - <0001

- .0058

 .0063

nw).

of determinations in the range 0.005 to 0.05: standard decomparisons, 7.

TABLE 37. Determinations l of molybdenum, in percent, in 

check samples

[Add 259500 to each sample number to form serial number]

Sample

28. 

33. 

37 

39. 

46 

48. 

49 

63 

92 

94. 

A

0.0001

.0002

<.0001

.0002

.0001

.0009

.035

.0018

.0002

<.0001

B

0.0001

.0003

.0001

.0005

.0002

.0012

.032

.0023

.0005

.0002

Mean

0.0001

.0003

<.0001

.0004

.0002

.0011

.034

.0021

.0004

.0001

Difference 

(max 

 min)

0

.0001

.0001

.0003

.0001

.0003

.003

.0005

.0003

.0002

Standard 

deviation

0

.00009

.00009

.00027

.00009

.00027

.0027

.00044

.00027

.00018

i Precision and reliability of determinations in the range 0.0005 to 0.005: standard 

deviation, 0.00029; number of comparisons, 2.

A. Alpha-benzoinoxime precipitation, method 1; Dorothy Ferguson and Claude

Huffman, analysts. 

B. Cupferron separation, method 3; Marian Schnepfe and Frank Orimaldi, analysts.

URANIUM, FLUOROMETRIC METHOD

[Range in shale: 0.00005 to 0.003 percent uranium] 

PRINCIPLES

The extraction procedure for the fluorometric determination of uranium is based on the method of Grimaldi 

and others (1954). Uranyl nitrate is extracted from 

nitric acid solution with ethyl acetate, using aluminum 

nitrate as a salting agent. A portion of the extract 

is evaporated and the residue fused with a carbonatefluoride flux to prepare a fluorescent melt. The extraction separates uranium from most elements that quench 

its fluorescence in the melt. The sample is usually 

completely decomposed by treatment with nitric and 

hydrofluoric acids; any undecomposed sample remaining is fused with sodium carbonate and dissolved in 

nitric acid. The relative fluorescence of the prepared 

phosphor is determined in a sensitive transmissiontype fluorometer calibrated with phosphors containing known amounts of uranium.

APPARATUS AND REAGENTS

Fluorometer: Suitable fluorometers are described by Grimaldi 

and others (1954), Kinser (1954), Parshall and Rader (1957), 

and Galvanek and Morrison (1954).

Machine for preparing phosphors: The one described by 

Stevens and others (1959) is advantageous for routine work, 

but suitable phosphors also can be prepared manually over 

a burner.

Shallow platinum dishes, about 7-ml capacity: Described by 

Grimaldi and others (1954, p. 103).

Platinum dishes, about 60- to 100-ml capacity.

Platinum-tipped tongs: The curved-tipped (Blair) and straighttipped tongs are both useful.

Centrifuge: A large centrifuge with adapters to hold test tubes 

about 145 mm long is advantageous but not necessary.

Motor-driven shaking machine: Equipped to extract a suite of 

solutions in test tubes at one time.

Test tubes, Pyrex, standard taper 19/17, 22 by 145 mm.
A-32 ANALYTICAL METHODS IN GEOCHEMTCAL INVESTIGATIONS OF THE PIERRE SHALE

Aluminum nitrate, A1(NO3)3-9H2O: This reagent must be substantially free from uranium, as determined with blanks 

carried through the method. Two or three extractions of the 

acid solution of the salt with ether followed by recrystallization from 10 percent nitric acid v/v generally yield a satisfactory product.

Flux: 45.5 percent by weight sodium carbonate, 45.5 percent 

potassium carbonate, and 9.0 percent sodium fluoride (Grimaldi and others, 1954). It is essential that all ingredients 

in the flux be of very fine and equivalent mesh size and thoroughly mixed.

Ethyl acetate, anhydrous, reagent grade.

Standard uranium solution, 1.0 ml = 1 mg U: Weigh and transfer 

1.1804 g black uranium oxide, at least 99.9 percent U3Og, to a 

1-liter flask. Dissolve by warming the uranium in sufficient 

nitric acid to make the final solution 7 to 8 percent v/v nitric 

acid and dilute to 1 liter.

Diluted uranium standard: Various concentrations of dilute 

uranium solutions in 7.5 percent nitric acid v/v are required. 

Prepare the dilute solutions frequently as needed to avoid 

possible loss of uranium to the glass during storage.

PROCEDURE

1. Transfer 1.0-g sample to a 60-ml platinum dish.

2. Ignite the sample over a burner to destroy organic matter.

3. Cool the sample and moisten with a few drops of water. 

Add 5 ml of nitric acid, place the dish on a steam bath and 

evaporate to dryness.

4. Add 10 ml nitric acid and 10 ml hydrofluoric acid to the dish 

and evaporate to dryness again. Repeat step 4 if undecomposed sample remains.

5. Add 10 ml nitric acid to the residue and evaporate to dryness 

to break up insoluble fluorides. Repeat this step to remove 

as much fluoride as possible.

6. Digest the residue with 30 ml water and 7 ml 1+1 nitric acid 

and filter the solution through a small filter paper into a 

100-ml volumetric flask.

7. Ignite the paper in a platinum crucible and fuse the residue 

with a minimum amount of sodium carbonate.

8. Dissolve the fusion cake in 10 ml of hot water by digestion in 

the covered crucible on the steam bath. Add a drop or two 

of methyl orange indicator and then add dilute nitric acid 

dropwise until the solution is just red, and combine with 

the original solution. Add sufficient 1+1 nitric acid to 

the flask to make the solution 7 percent v/v in nitric acid 

after dilution and dilute to 100 ml with water.

9. Transfer 5 ml of the sample solution to a test tube, made to 

hold a ground-glass stopper, which contains 9.5 g of aluminum nitrate.

10. Immerse the tubes containing the sample solutions in hot 

water to dissolve the aluminum nitrate. Cool the tubes to 

room temperature, add exactly 10 ml of ethyl acetate to 

each tube, stopper, and place the tubes in a shaking 

machine.

11. Shake the tubes for 2 minutes and remove from the shaker. 

Either allow the solutions to stand for a few minutes to 

separate into layers or place the tubes in a centrifuge to 

separate the solutions.

12. Filter a portion of the upper ethyl acetate layer in each tube 

through dry 7- or 9-cm dense filter paper into dry, clean 

tubes.

13. Arrange the platinum flux dishes in the same order in a shallow 

pan containing about an eighth of an inch of cold water 

or arrange them on several thicknesses of wet-paper 

toweling.

14. Pipet 2-ml aliquots of each of the filtered ethyl acetate 

extracts and transfer them to each dish in order, igniting 

the ethyl acetate after each transfer with a match or 

lighted taper.

15. When the ethyl acetate has finished burning, a small residue 

and perhaps a few drops of acetic acid will remain. Dry 

this on a steam bath or by careful heating on a hot plate, 

and burn off the organic residue, including any residual 

nitric acid, below 500° C over a burner.

16. Transfer 2.0 g of the premixed carbonate-fluoride flux to 

each dish. Weigh the flux with a sensitive torsion or 

trip balance.

17. Prepare the phosphors by fusing the flux at as low a temperature as possible (below 700° C), swirling the molten flux 

over the entire area inside the dish. This is done best 

by placing the dishes on the quartz rods of the rotating disk of the phosphor machine (Stevens and others, 

1959). The fusion requires about 4 to 5 minutes with the 

machine in the tilted position. Level the machine 

and anneal the melts by allowing the machine to run for 

10 minutes after the gas is turned off. If the phosphor 

melts are prepared manually, follow the instructions given 

by Grimaldi and others (1954). In any event, the melt 

must be cooled slowly to achieve the maximum and most 

reproducible fluorescence, and all standards must be prepared the same way.

18. Compare the fluorescence of phosphors containing unknown 

amounts of uranium with phosphors containing known 

amounts of uranium, using a sensitive, stable fluorometer.

19. Calculate the percentage of uranium in the samples.

STANDARD CURVE

Transfer aliquots of standard uranium solution containing 0, 0.01, 0.02, 0.03, and 0.04 micrograms of 

uranium to test tubes containing 9.5 g aluminum nitrate 

and continue the determinations, beginning at step 9 

of the procedure.

The sensitivity of fluorometers can be adjusted within wide limits. Laboratory B reported that 50 scale 

divisions on the fluorometer corresponded to 0.09 micrograms of uranium. When so adjusted readings of three 

scale divisions were obtained for the reagent blank and 

eight scale divisions for a sample solution containing 

1 ppm uranium. Laboratory A reported that 100 scale 

divisions on the fluorometer corresponded to 0.044 

micrograms of uranium. When so adjusted readings 

of 13 scale divisions were obtained for the reagent 

blank and 33 scale divisions for a sample solution containing 1 ppm uranium.

PRECISION OF URANIUM DETERMINATIONS

Uranium was determined fluorometrically on the 80 

samples of shale in laboratory B by two analysts. 

The ranges of concentration for uranium were from 

0.00005 to 0.0005 percent (48 samples) and 0.0005 to 

0.005 percent (32 samples). The results of the two 

analysts are compared in tables 38, 39, and 40. The 

results on the hidden splits are given in table 39 and 

those on the check samples in table 40. The results 

of B on the check samples are compared with those of 

BI and A graphically on figure 13.
CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-33

825 025

URANIUM, IN PARTS PER MILLION 

LABORATORY Bj

25

URANIUM, IN PARTS PER MILLION 

LABORATORY A

FIGURE 13. Comparison of uranium determinations of B with those of BI and A.

TABLE 38. Determinations 1 of uranium, in percent, by different 

chemists, in laboratory B

[Add 259500 to all sample numbers, except 00 to 05 to which add 259600, to form serial

numbers]

Sample

57 .....

88 

36 ....

29 

35. 

38 __

30 

45 - 

50... .....

70.. ...

79 

69. 

32 

34... .....

41 

51 

58 

31 _ 

B

0.00009

.00010

.00016

.00017

.00023

.00024

.00028

.00026

.00028

.00026

.00026

.00028

.00031

00031

.00033

.00032

.00033

.00035

B,

0 00008

.00012

.00013

.00014

.00016

.00020

.00025

.00024

.00028

.00028

.00024

00031

.00026

.00027

.00032

.00030

.00029

.00028

Sample

TO

60

64

66 

77 __ -

85 .... 

on

89 __ -

84 . .

81 

75 

76 

74. _ 

CO

27 

43

78. _ -

QO

B

0.00034

.00034

.00033

00030

.00031

00033

00032

.00034

.00034

00037

.00037

.00039

.00043

(\Of\AK

.00045

.00049

.00050

.00052

B,

0 00032

.00031

00034

00033

.00034

00034

.00038

00037

.00036

nnn^to

.00035

.00039

.00043

.00045

nnru.7

nnncn

.00050

nnnrro

Sample

40. __ .

67 __ ..

87 

83 

55 ___

71 

62. .

72. .....

42 

44

47 

91. _ 

54. _ -

*K

QK

73 

26. _ -

61. _ -

B

0.00055

.00050

.00053

.00057

.00058

.00063

.00063

.00070

.00087

00087

.00085

.00085

.00089

nnnQ4

.00096

0012

.0018

.0029

B,

0.00056

.00054

.00052

.00059

.00056

.00064

.00070

.00068

.00083

.00076

.00094

.00090

.00079

nnnon

.0010

.0012

.0017

.0026

1 Precision and reliability of determinations:

Standard Number of

Range deviations comparisons

0.00005-0.0005----.___.___-_______ .___ 0.000022 33 

.0005 - .005___ -.__.______.___........ .000058 21

B. Fluorometric method; Ivan Barlow, analyst. 

BI. Fluorometric method; Joseph Budinsky, analyst.

TABLE 39. Determinations l of uranium, in percent, in hidden

splits

[Add 259500 to all sample numbers, except 00 to 05 to which add 259600, to form serial 

numbers. Groups indicate the samples that were duplicates]

Sample

33 . .

97 

49... _ ..

96.. ......

99... .....

03... .....

B

0.00013

.00016

.00079

.00073

.00076

.00078

Bi

ft nnni9

.00016

.00076

.00077

00080

fWYTft

Sample

CO

04

65 

no

68 

01 

B

O fififift9

.00077

00036

00039

00045

.00042

Bi

0 00080

f¥VY7ft

00038

.00039

f]fy\AQ

.00043

Sample

80

00

82

02 

05 

B

0.00035

00031

.0021

nniQ

nniyio

.00032

B,

0.00034

nnn^n

.0021

.0021

.00032

.00033

1 Precision and reliability of determinations:

BBl.... ...... ... ........ ... -

B, B, ... .... __ .....

Range

0.00005 to 0.0005

Standard 

deviation

0.000040 

.000022 

.000010

Number of 

comparisons

5 

5 

10

0.0005 to 0.005

Standard 

deviation

0.000090 

.000028 

.000015

Number of 

comparisons

8 

8 

8

B. Fluorometric method; Ivan Barlow, analyst. 

Bj. Fluorometric method; Joseph Budinsky, analyst.

TABLE 40. Determinations l of uranium, in percent, in the 

check samples

[Add 259500 to each sample number to form serial number]

Sample

28 

33 . ....

37 

39..-- 

46-.- .

48- ____

49 

63 .

Q9

94

B

0.00015

.00013

.00092

.00055

.00047

.00031

.00079

.0024

.00094

.00040

B,

0.00016

.00012

.00097

.00050

.00052

.00027

.00076

.0023

.00095

.00039

A

0.00020 0.00017

.00014 .00013

.0011 .0011

.00057 .00062

.00052 .00052

.00029 .00025

.00091 .00085

.0026 .0025

.0011 .0010

.00037 .00038

Mean

0.00017

.00013

.0010

.00056

.00051

.00028

.00083

.0025

.0010

.00039

Difference (max 

min)

0.00005

.00002

.00018

.00012

.00003

.00006

.00015

.00030

.00016

.00003

Standard deviation

0.000024

.000010

.000088

.000058

.000015

.000029

.000073

.00015

.000078

.000015

Precision and reliability of determinations:

Average of A compared with 

average of B and Bi. 

All data . ___

Range

0.00005 to 0.0005

Standard 

deviation

0.000015 

.000018

Number of 

comparisons

4 

24

0.0005 to 0.005

Standard 

deviation

0.000012 

.000081

Number of 

comparisons

6 

36

B. Fluorometric method; Ivan Barlow, analyst. 

Bi. Fluorometric method; Joseph Budinsky, analyst. 

A. Fluorometric method; Edward Fennelly, analyst.

CARBON

CARBONATE CARBON, GASOMBTRIC DETERMINATION

[Range in shale: 0.02 to 8 percent carbonate carbon] 

PRINCIPLES

Carbon dioxide is liberated by the action of 1 + 1 

hydrochloric acid on the sample. The volume of the 

liberated carbon dioxide plus the air present in the 

reaction flask is measured at a definite temperature 

and atmospheric pressure. The combined gases are 

then scrubbed free of carbon dioxide by passage 

through an alkali solution. The volume of the residual 

gases is again measured at the same temperature and 

pressure. The difference in the observed volumes, due 

to the volume of carbon dioxide, is calculated to 

standard conditions of temperature and pressure, 

using the ideal gas relationships. The weight of carbon 

dioxide is then calculated from its volume at standard 

temperature and pressure. The method is an adaptation made by I. C. Frost from procedures in books 

(TreadweU and Hall, 1947, p. 328-339; Association of 

Official Agricultural Chemists, 1950, p. 118-119)

SPECIAL EQUIPMENT

The apparatus for the liberation, measurement, and absorption 

of carbon dioxide (fig. 14) consists of a reaction flask, a, of 

approximately 30-ml capacity, fitted with a two-hole stopper. 

A small separatory funnel, b, entering one hole of the stopper, 

is used to introduce the acid for liberation of carbon dioxide 

from the sample. A small water condenser, c, is placed in the 

second outlet that in turn leads through a two-way stopcock,
A-34 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALB

Reaction

Separator/ funnel

Water condenser

Two-way stopcock

Gas-measuring burette

Water jacket

Thermometer

Burrell auto-bubbler

Leveling bulb for 50 percent KOH

Leveling bulb for 1+4 HCI saturated

with sodium chloride

Bunsen burner

Acid reservoir

FIGURE 14. Apparatus for gasometrlc determination of carbon dioxide.
'CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIEEJRE SHALE A-35

d, at the top of a gas-measuring burette, e, of 100-ml capacity. 

The gas-measuring burette is enclosed in a glass tube of sufficient 

diameter (50 mm) to serve as a cooling water jacket, /, for the gas 

burette and to help maintain a relatively constant temperature. 

The water-jacket inlet at the bottom is attached to the water 

supply, and cooling water is circulated through the jacket 

during use. A thermometer, g, is suspended in the water 

jacket for reading the temperature of the water and indirectly 

that of the gas in the burette. The other side of the two-way 

stopcock, d, leads to a Burrell auto-bubbler, h, for absorption 

of carbon dioxide. The outlet from the Burrell auto-bubbler 

is attached to a leveling bulb, i, containing 50 percent w/v 

potassium hydroxide solution. Sufficient potassium hydroxide 

solution to completely fill the auto-bubbler plus 100 ml excess 

is required.

The outlet from the bottom of the gas burette is connected 

with a leveling bulb, j, containing 1 + 4 hydrochloric acid 

saturated with sodium chloride. Methyl red indicator also is 

added to color this solution and facilitate readings of gas volumes. 

The apparatus is supported on a frame. Open ring supports 

are used to adjust the leveling bulbs to the heights required for 

operation of the equipment. A Bunsen burner, k, and acid 

reservoir, I, complete the gasometric apparatus.

A barometer located near the apparatus is used to determine 

the atmospheric pressure.

PROCEDURE

1. Accurately weigh and quantitatively transfer to the reaction 

flask an appropriate weight of sample to yield from 5.0 

to 50.0 ml of carbon dioxide, as shown in figure 15. Usually 

0.2 to 5 g is required. Add 2 or 3 glass beads and approximately 10 ml of water to the sample. When the sample 

contains sulfides, add approximately 0.1 g of mercuric 

chloride to the reaction flask to prevent liberation of 

hydrogen sulfide.

2. Adjust the gas-burette leveling bulb to completely fill the 

gas burette with acidified sodium chloride solution.

3. Attach the reaction flask tightly to the stopper bearing the 

condenser and small separatory funnel. Close the stopcock 

on the separatory funnel and turn the stopcock at the top 

of the gas burette to connect the gas burette with the

FlGUBE

VOLUME OF CARBON DIOXIDE AT STP. IN MILLILITERS

15. The relation between the percentage of carbon dioxide in the sample 

and its volume at standard conditions.

10

11

reaction flask. Clamp the leveling bulb in position well 

below the water level in the gas burette to give reduced 

pressure in the system.

Pour 20 ml of 1 + 1 hydrochloric acid into the separatory 

funnel and open the stopcock just enough to allow the 

acid to slowly enter the reaction flask and react with 

carbonate in the sample. During the liberation of carbon 

dioxide from the sample, keep the pressure in the gas burette 

below atmospheric pressure by adjusting the leveling bulb. 

After the reaction has subsided, heat the reaction flask and

boil the solution for 2 to 4 minutes.

Purge the reaction flask and condenser of all gas by passing 

water through the separatory funnel into the reaction flask, 

condenser, and just up to the stopcock above the gas burette 

This is accomplished by lowering the gas-burette leveling 

bulb and closing the stopcock when the water has reached 

it.

Wait 2 to 3 minutes for the gas to adjust to the temperature 

of the water jacket. Read and record the temperature in 

the water jacket.

Adjust the liquid level in the burette leveling bulb to that in 

the gas burette by holding the bulb against the burette and 

moving it up or down as required to match the levels. 

Read and record the volume (A) of gas in the burette. 

Raise the leveling bulb and adjust the stopcock above the 

gas burette to allow the gas to pass slowly through the 

Burrell auto-bubbler. Lower the leveling bulb to return 

the gas to the burette. Repeat three times. Finally close 

the stopcock above the gas burette when the caustic absorbing solution has reached a fixed point in the capillary 

leading to the stopcock.

, Wait 2 to 3 minutes for the gas to adjust to the temperature 

in the water jacket. Read and record the temperature in 

the water jacket.

, Adjust the gas to atmospheric pressure with the leveling 

bulb, as in step 8, and read and record the volume (B) 

of gas in the burette. 

Read and record the barometric pressure. 

Calculate the CO2 content of the sample as follows : Reduce 

the observed volume of gas to 0°C (273° K) and 760 mm 

pressure by substituting determined values in the following formula and solving for Vs, where Vs = volume of CO2 

calculated to standard conditions.

Vs _ ~

(A-£)XPX273 

760 (273+<)

_ s ~

P(A-B)

where A= total volume of gas measured in milliliters; 

B= residual volume of gas, in milliliters, after absorption 

of CO2 ; P= observed barometric pressure, in millimeters 

of mercury, after instrumental correction for temperature ; 

and t= observed temperature, in °C. Using the value of 

Vs obtained, the percentage CO2 is calculated as follows:

Percent CO2=

or percent CO2 =

VsX 44.011X100

22,269X W 

VsX 0.1976

where 44.011 = weight of 1 mole of CO2) in grams; 22,269 = 

volume of 1 mole of CO2 , in milliliters, at 0°C and 1 

atmosphere; and W=weight of sample, in grams. The 

calculated value of CO2 is multiplied by 0.2727 to obtain 

the percentage of carbon when this conversion is desired. 

Table 41 gives factors for calculating CO2 and C for various 

sample weights from the volume of carbon dioxide at
A-36 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALE

0°C and 1 atmosphere. Factors for vari us conditions of 

temperature and pressure for a sample weight of 1.7 g 

are tabulated by the Association of Official Agricultural 

Chemists (1950, p. 871). The analyst can calculate these 

factors advantageously for other sample weights.

TABLE 41. Factors for calculating percent of carbon dioxide and 

percent of carbon for various sample weights from the volume 

of carbon dioxide under standard conditions

[Multiply volume of COj at STP by factor corresponding to weight of sample]

Factor for Factor for 

Sample weight (grams) percent COj percent C

0. 0500__________________________ 3.9527 1.0787

. 1000... _______________________ 1.9763 .5394

.2000--__-_-_______________.___ .9882 .2697

.2500-_-_---___________________ .7905 .2157

.3000__________._______________ .6581 .1798

.4000-_. _ ____________________ .4941 .1348

crwin onco 1/^*711

1.0000__-_ ____________________ .1976 .05394

5. 0000-_--__--_-.___. ___________ .03953 .01079

PRECISION OF CARBONATE CARBON DETERMINATIONS

Carbonate carbon was determined on the 80 samples

TABLE 42. Determinations l of carbonate carbon, in percent, by 

different methods and laboratories

[Add 259500 to each sample number to form serial number]

Sample

51 

83 

79 

44... ...

35 

32........

36 

50 

74 

78 

89 

42.... _ .. 

67 

69 .-.

A

0.06 

.08 

.09 

.10 

.11 0.11

.12 

.14 

.14 .19

.19 

.19 

.21 

.24 

.23 .24

.25 .25

C

0.09

.19

.20

........

D

0.13

.03

.11 

.13 

.15

.14

.17

.23

.20

.24

.19

Sample

45

38

85

70

75

77

64

76

34

47

62.

60 

41

A

0.27 0.28

.35 

.36 .37

.47 .48

.53 .56 

.58 

.59 

.61 

.61 .62

.76 .76 

2.4 

2.9 3.0 

5.9 6.0 

6. 8 6. 9

C

0 56 

56

77

2.9

6.9

D

0.20 

.35 

.44 

.55

.95 

.46 

.57

2.5

5.9

' Precision and reliability of determinations:

A _ ----- --- _- ----- _ _

A, C 

A, D

Range

0. 05 to 0. 5

Standard 

Deviation

0.014 

.016 

.034

Number of 

comparisons

7 

3 

22

0.5 to 5

Standard 

deviation

0.011 

.036 

.14

Number of 

comparisons

4 

7 

5

of shale in laboratory A by the gasometric method 

described. The ranges of concentration for carbon 

were <0.05 percent (31 samples), 0.05 to 0.5 percent 

(31 samples), 0.5 to 5 precent (15 samples), and >5 

percent (3 samples). The lowest range is not included 

in calculations because of the 0.02 percent carbon 

cutoff level generally used with the method. The percentages of carbon dioxide reported on the shale by 

laboratories A, C, and D, calculated to carbonate 

carbon, are given in tables 42, 43, and 44. The results 

of replicate determinations are given in table 42, those 

on the hidden splits in tables 43, and those on the check 

sample in table 44. The results of A on the check 

samples are compared with those of AI and those of 

C+D in figure 16.

zlO

CARBONATE CARBON, IN PERCENT 

LABORATORY A,

CARBONATE CARBON, IN PERCENT 

LABORATORY C + D

FIGURE 16. Comparison of carbonate carbon determinations of A with those of AI 

and of C+D. Plots that coincide are indicated with the number involved.

A. Gasometric method described; Edward Fennelly, analyst.

C. Absorption tube-gravimetric method, (Hillebrand and others, 1953, p. 768-770); Marguerite Seerveld and Vertie Smith, analysts.

D. Gasometric method (Shapiro and Brannock, 1956); Leonard Shapiro, Paul Elmore, Samuel Botts, and Marvin Mack, analysts.

TABLE 43. Determinations 1 of carbonate carbon, in percent, in 

hidden splits

[Add 259500 to all sample numbers, except 00 to 05 to which add 259600, to form serial 

numbers. Groups indicate the samples that were duplicates]

Sample

33 

97 

49 

96 

99.. .

03. 

53 

04 

65 

98 

A

1.5 

1.5

<.02 

<.02 

<.02

<.02

4.8 

4.8

.08 

.10

C

1.5

!oi

4.8

.09

D

1.5

.02 

.02

4.8

.11

Sample

68

01

80

00

82

02.

86

05

A

0.34 

.33

.66 

.65

.21 

.21

.02 

.02

C

0.35

.67

.23

<.01

D

0.30

.65

.14

.02

1 Precision and reliability of determinations:

A ............... ...

A, C.... ..... 

A, D.. .......... 

Range

0. 05 to 0. 5

Standard 

Deviation

0.0024 

.012 

.028

Number of 

comparisons

3

6 

6

0. 5 to 5

Standard 

deviation

0.005 

.008 

.005

Number of 

comparisons

3

6 

6

A. Gasometric method described; Edward Fennelly, analyst.

C. Absorption tube-gravimetric method (Hillebrand and others, 1953, p. 768-770); 

Marguerite Seerveld and Vertie Smith, analysts.

D. Gasometric method (Shapiro and Brannock, 1956); Leonard Shapiro, Paul Elmore, Samuel Botts, and Marvin Mack, analysts.
-CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-37

TABLE 44. Determinations l of carbonate carbon, in percent, in 

check samples

[Add 259500 to each sample number to form serial number]

Sample

28

33 -..--.....-. ..

37......................

39 ...................

46 .... .............

48.. .............. ...

49 -.._-.... -

63 .................

92....... _ ............

94.. _ .................

A

7.9 

1.5 

.04 

.04 

.02 

<.02 

<.02 

<.02 

<.02 

.67

A,

7.7 

1.5 

.13 

.07 

.02 

<.02 

<.02 

<.02 

<.02 

.66

C

1.5

II

D

7.4

.11

.11 

.08

.02 

.65

Mean

7.7 

1.5 

.09 

.07 

.04 

<.02

<.02

<.02

<.02 

.66

Difference (max 

min)

0.5 

0 

.09 

.07 

.06

.02

Standard deviation

0.24 

0 

.043 

.034 

.029

.010

i Precision and reliability of determinations:

A, AI.............. .......

A, C+D ..................

Range

0. 05 to 0. 5

Standard 

Deviation

0.048 

.048

Number of 

comparisons

2 

2

0.5to5

Standard 

deviation

0.005 

.010

Number of 

comparisons

2 

2

A. Gasometric method described; Edward Fennelly, analyst.

Ai. Gasometric method described; Irving Frost, analyst.

C. Absorption tube-gravimetric method (Hillebrand and others, 1953, p. 768-770);

Marguerite Seerveld and Vertie Smith, analysts. 

D. Gasometric method (Shapiro and Brannock, 1956); Leonard Shapiro, Paul

Elmore Samuel Botts, and Marvin Mack, analysts.

TOTAL CARBON, QASOMETRIC DETERMINATION

[Range in shale: 0.2 to 9 perceut total carbon]

PRINCIPLES

Organic matter is oxidized and converted to sodium 

carbonate by heating with sodium peroxide in a Parr 

microbomb in the presence of small amounts of potassium perchlorate and magnesium powder that act as 

combustion aids. The fused sample is leached from 

the bomb, and the peroxide is decomposed by removal 

of excess oxygen by gently heating the solution while 

covered to avoid absorption of carbon dioxide from the 

air. The carbon dioxide is liberated with hydrochloric acid and determined gasometrically, as described 

previously under the determination of carbonate carbon. A blank run is made to correct for the carbonate 

content of the sodium peroxide used. The method is 

that of I. C. Frost (written communication, 1955).

The method is applicable to carbonaceous materials 

that can be reduced to fine powder. Samples of coal, 

asphaltites, graphite, and unidentified carbonaceous 

materials have all been satisfactorily analyzed by using 

this method.

APPARATUS AND REAGENTS

Apparatus for the liberation, measurement, and absorption of 

carbon dioxide: Described under determination of carbonate 

carbon.

Complete Parr microbomb assembly with sodium peroxide 

measure.

Air-gas blast burner adjustable to a fine-pointed flame.

Additional fusion cups with a sufficient number of covers for

several oxidations to be made in sequence. 

Sodium peroxide: Fresh, dry sodium peroxide must be used.

After use, the reagent should be stored in a tightly closed bottle

in a desiccator. 

Magnesium powder, reagent grade: The metal is washed with

acetone to remove traces of organic matter and then dried

before use.

PROCEDURE

1. Accurately weigh a sample of 0.050 to 0.50 g, depending on 

the apparent organic-matter content, and transfer to the 

fusion cup of a Parr microbomb. A 0.50-g sample is the 

maximum that can be oxidized in the parr microbomb, but 

a smaller sample size must be used when much organic 

matter is present because the oxidation is rapid and the 

reaction is difficult to control. A 0.050-g sample yields 

sufficient carbon dioxide for the determination and minimizes the hazard of the fusion.

2. Add 1 measure (about 1.25 g) of sodium peroxide, about 50 

mg of potassium perchlorate, and 75 mg of magnesium 

powder to the fusion cup.

3. Place cover on the fusion cup and fasten in place. Shake the 

cup vigorously for several minutes to insure complete mixing of reagents. Open the cup and add sufficient additional 

sodium peroxide to just cover the fusion mixture. Clamp 

the lid on the fusion cup securely.

4. Heat the fusion cup and contents over an air-gas blast 

flame behind a safety shield, until oxidation occurs. Oxidation is generally shown by a dull redness or a noticeable 

blue coloring of the fusion cup.

5. Cool the fusion-cup assembly by immersion in cold water. 

Transfer the lid and cup to a reaction flask and slowly add 

sufficient water to cover the fusion cup. It is essential 

that the bomb be cooled immediately after the fusion, 

otherwise the lead gasket in the lid may be destroyed.

6. Place the reaction flask upright in a beaker containing water, 

cover the flask by inverting a small beaker over it, and heat 

the solution on a water bath for at least an hour to decompose the peroxide and remove excess oxygen from the 

solution.

7. Wash down the sides of the reaction flask with a small stream 

of water and attach it to the gas-liberation apparatus.

8. Liberate and measure carbon dioxide, as described in the 

method for determination of carbonate carbon.

9. Determine carbon dioxide in the reagents in a similar manner 

to obtain the reagent blank.

10. Calculate the total carbon content of the sample as follows: 

Convert the observed volume of gas to 0°C (273°K) and 

760 mm pressure by substituting determined values in the 

formula given for this purpose in step 13 of the gasometric 

determination of carbonate carbon (p. A-35). Calculate the 

volume of carbon dioxide due to the reagent blank to standard conditions. The difference between the two volumes is 

the volume of carbon dioxide due to the sample.

Percentage of total carbon

VsX 12.01X100

Vs

18.542XTP

where Vs= volume of CO2 corrected for reagent blank 

and corrected to standard conditions; 12. 01 = atomic 

weight of carbon, in grams; 22, 269 = volume of 1.0 mole of 

CO2 , in milliliters, at standard temperature and pressure; 

and W= weight of sample, in grams.
A-38 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALE

PRECISION OF TOTAL CARBON DETERMINATIONS

Total carbon was determined on the 80 samples of 

shale in laboratory A by use of the gasometric method 

described. The ranges of concentration for total carbon 

were <0.2 to 0. 5 percent (27 samples), 0. 5 to 5 percent 

(38 samples), and >5 percent (15 samples). Because 

0.2 percent total carbon is the threshold limit of the 

determination, no deviations have been calculated for 

determinations below this level of concentration. The 

results on replicate determinations are given in table 

45, those on the hidden splits in table 46, and those on 

the check samples in table 47.

The determinations of total carbon on the check 

samples by A, using the gasometric method, are plotted 

in figure 17 against those of A2 , using the same method.

TOTAL CARBON, IN PERCENT 

LABORATORY A2

FIGURE 17. Comparison of total carbon determinations of A with those of A».

TABLE 45. Replicate determinations : of total carbon, in percent, 

by laboratory A

[Analysis by gasometric method described; Edward Fennelly, analyst. Add 259500 

to all sample numbers, except 00 to 05 to which add 259600, to form serial numbers]

42

65

67

50

05

30

35

29

90

34.

80

 .26 .27

 ----- .28 .29

 .28 .47

. - .30 .37

 - .40 .43

 - .41 .48

 .41 .49

... .49 .51

... - .67 .69

 .. .75 .810.84 

 .76 .79

.88 .91

85 

45- 

43 

75. 

55__ 

70 -

47 

63-. -

7Q

26 

95_

1 Precision and reliability of determina

Range 

0.05 - 0.5- _____________

.5-5 ... ... ...

5 - 50 _ ....... _

.89 .94 

. 94 1. 1 

.96 1.1 

1.0 1.1 

1.0 1.1 

1.1 1.1 

1.1 1.2 

1.8 2.0 

i.l 2.2 

3.0 3.1 3.3 

3.3 3.3 

4.4 4.7 

4.8 5.2 

4. 9 4. 9 5. 0 

lions:

01

02 

60 

82 

04 -. 

03 - 

28 - 

98 -

49

Standard 

deviations 

n ftf.fi

 ..__. .16

 .... _ .. .57

.... 5.7 5.7

 . 6.6 6.8

8.4 8.5 

6.6 6.6

 . 6.6- 6.8

7

O 7 Q

77 7 Q

8.0 8.3

8

1 Q I

 - 8.2 8.3 

 . 8.4 8.5

Number of 

comparisons 

8 

42 

20

TABLE 46. Determinations 1 of total carbon, in percent, in 

hidden splits by laboratory A

[Analysis by gasometric method described; Edward Fennelly, analyst. Add 259500. 

to all sample numbers, except 00 to 05 to which add 259690, to form serial numbers 

Groups indicate the samples that were duplicates]

0.84 

.88

6.7 

7.4

.45 

.42

33 

97 

49

Qfi

99 

03. 

... 1.8

 1.9

 ... ... 8.5

8

0

 8.2

 8.0

53 

04 

65. 

98. - _ .

68 

01 

 7.4

 7.3

 .... .29

 .27

94

... .99

80. 

00 

82- . .

02. 

Sfi

05 

i Precision and reliability of determinations:

Range

0.50 -0.5.

.5 - 5 .

5 - 50..

Standard Number of

deviations comparisons

0.018 2

.048 3

.20 8

TABLE 47. Determinations J of total carbon, in percent, in check 

and other samples

[Add 259500 to each sample number to form serial number]

Sample

26 

28 . 

31 - 

32 

33 

37- __ - _

39 _ - - 

46

47 

48 . _ - _ 

49 . ___ - _

60 

63 

97

O9

94

A

4.8

8.1

.8

1.0

1.8

<.2

<-2

.5

2.0

<-2

8.5

6.6

3.1

.9

5.7

.8

1.5

Ai

0.8

1.0

........

2.2

.8

A,

7.6

2.4

.2

<.2

.4

<-2

8.3

3.2

1.0

1.3

A3

4.9

.9

1.1

2.4

6.6

.8

5.8

Mean

4.9

7.9

.8

1.0

2.1

.2

<.2

.5

2.4

<.2

8.4

6.6

3.2

.8

5.8

.9

1.4

Difference (max 

min)

0.1

.5

.1

.1

.6

.2

. .... ...

.4

 .....

0

.1

.1

.1

.2

.2

Standard deviation

0.06

.30

.06

.06

.35

.12

"""06

.24

 -..-.

0

.06

.06

.06

.12

.12

1 Precision and reliability of determinations in the range 0.5 to 5:

Standard Number of 

deviation comparisons

All dataAll methods.

0.17 

.24

17

9

A. Gasometric method; Edward Fennelly, analyst.

Ai. Gasometric method; Wayne Mountjoy, analyst.

Aj. Gasometric method; Irving Frost, analyst.

A». Tube furnace-combustion train; Wayne Mountjoy, analyst.

DETERMINATIONS OF ORGANIC CARBON

[Range in shale: 0.2 to 9 percent organic carbon]

Organic carbon determinations are based on separate determinations of total carbon and carbonate 

carbon, the difference being taken as organic carbon.

Organic carbon was calculated for the 80 samples of 

shale by using the data obtained in laboratory A for 

total and carbonate carbon. The lower cutoff limit of 

0.2 percent for the determination of total carbon 

applies also to organic carbon; 16 samples contained 

less than 0.2 percent organic carbon. The ranges of 

concentration for organic carbon in the other 64 samples 

were from 0.2 to 0.5 percent (21 samples), 0.5 to 5 

percent (34 samples) and > 5 percent (9 samples). 

The results of replicate determinations are given in 

table 48t those on the hidden splits in table 49, 

and those on the check samples in table 50. The 

results of A and AI on the check samples, using the 

same method, are compared in figure 18.
CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-39

10

o 

cr

LU 

Q_

cc 

o

GO <

<o 

o

o

0

10

ORGANIC CARBON, IN PERCENT 

LABORATORY Ax

FIGURE 18. Comparison of organic carbon determinations of A with those of At.

TABLE 48. Replicate determinations l of organic carbon, in percent, 

made in laboratory A by one chemist

[Calculated from total carbon minus carbonate carbon, using data of Edward 

Fennelly, analyst. Add 259500 to all sample numbers, except 00 to which add 

259600, to form the serial numbers]

TABLE 49. Determinations l of organic carbon, in percent, in 

hidden splits by laboratory A

[Calculated from total carbon minus carbonate carbon, using data of Edward 

Fennelly, analyst. Add 259500 to all sample numbers except 00 to 05 to which add 

259600, to form serial numbers. Groups indicate the samples that were duplicates]

TABLE 50. Determinations 1 of organic carbon, in percent, in 

check samples

[Add 259500 to each sample number to form serial number]

Sample

28

33

37

39

46

48

49

63

9?

94

A

<0.2 

.3

!4

sis

3.1

.8 

.8

A1

<0.2 

.9

J4

s!s

3.2 

1.0 

.7

Mean

<0.2 

.6

J4

&4 

3.2 

.9

.8

Difference 

(max min)

0.6

0

.2 

.1 

.2 

.1

Standard 

deviation

0.53

6

.18 

.09 

.18 

.09

1 Precision and reliability of determinations in the range of 0.5 to 5: standard 

deviation, 0.10; number of comparisons, 3.

A. Calculated from total carbon minus carbonate carbon, using data of Edward 

Fennelly, analyst. 

At. Calculated from total carbon minus carbonate carbon, using data of Irving Frost, 

analyst.

40 

00 

30 

75 

29. _

60 

85 .

45. 

90. 

43

 0.2 0.3

 .2 .3

 .4 .5

 .4 .6

 .5 .6

 . .6 .7

 .6 .7

 .7 .8

 .7 .7

. _ _ 1.0 1.1

47. 

55 

Sees. 

73 

26 

95 

61 

91 

i Precision and reliability of determinations:

Range 

0.05- 0.5 . _ ___________ - _

.5-5 . ......

5 -50 ...... .

Standard 

deviations 

...... 0.093

 .12

 .34

 1.0 1.4

 1.1 1.1

 2.8 2.9

 3.0 3.3

 3.3 3.3

 4.4 5.2

 4.9 5.0

 5.3 5.6

 5.7 5.7

Number of 

comparitons 

3 

13 

3

33. __ - ________ 0.3

97. __ .... .5

49. _ .... 8.5

96 8.2

99 8:2

no O A

1 Precision and reliability 

0. 05- 0. 5

53--. - 2.6 

04 .. 2.4

65 .2

98 <-2 

68. . .6

01 7

80 <0.2

00 .2 

82 __ 6.5

02.. 7.2 

86 .4

Ofi _. .4

of determinations: 

Standard Number of 

Range deviations comparisons 

. _ __ n 12 4

.5-5 .11 2

5 -50 -.. _ .25 7

ORGANIC MATTER

{Range in shale: 0.2 to 15 percent organic matter] 

PRINCIPLES

Organic matter in shale is generally believed to 

consist of a complex substance that is about 90 percent 

kerogen. This substance is slightly soluble in common 

organic solvents to the extent of about 5 percent and 

is intimately mixed throughout the shale making it 

difficult to separate from the inorganic constituents 

of shale.

In the chemical separation of organic matter, the 

shale is treated with hydrochloric and hydrofluoric 

acids, which do not appreciably alter or dissolve the 

organic matter. The acids decompose and dissolve 

most of the inorganic constituents of shale, with the 

exception of pyrite and related mineral compounds. 

The residue from the acid treatment is heated to constant weight at 80°C and then ignited at 1000°C; the 

loss on ignition is taken as a measure of the organic 

matter. Loss of water from hydrated materials in 

the residue during the ignition may cause errors in the 

results. Pyrite is substantially unattacked by the 

acid treatment and is corrected for by determining iron 

in the residue after ignition. The method is empirical 

and is not used to determine any specific type of organic 

matter. Similar separation procedures have been used 

by others (Guthrie, 1938) to separate organic matter 

from large samples for organic analysis and identification.
A-40 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALE,

APPARATUS AND REAGENTS

Platinum crucibles, 30- and 50-ml capacities, with lids.

Platinum dishes, 100-ml capacity.

Hard rubber or plastic funnels and beakers.

Hydrochloric acid, analytical grade.

Hydrofluoric acid, analytical grade.

PROCEDURE

1. Regrind a portion of the prepared sample pulp to pass a 

200-mesh sieve.

2. Weigh 1.0 g of the finely ground sample and transfer it to a 

50-ml platinum crucible.

3. Moisten the sample with water and add 20 to 30 ml of hydrofluoric acid slowly and cautiously to prevent spattering. 

Cover the crucible tightly and digest on the steam bath 

over night.

4. Cool the hydrofluoric acid solution in the crucible and filter 

it through an 11-cm hardened paper, using a plastic funnel 

and beaker. Work under a fume hood and guard against 

exposure to hydrofluoric acid or its vapor.

5. Transfer the residue from the filter paper back to the original 

crucible with a stream of water. Add hydrochloric acid 

equal to about one-half the volume of the solution in the 

crucible, cover, and digest for about 4 hours on the steam 

bath.

6. Filter the solution on hardened paper and thoroughly wash the 

residue with hot water.

7. Transfer the residue from the paper with a stream of water to 

a tared 30-ml platinum crucible. Carefully dry the residue 

on the steam bath and finally in an oven to constant 

weight at 80° C. Cool and weigh.

8. Ignite the organic matter for 1 hour at 1000°C. Cool and 

re weigh.

9. Examine the residue for Fe2O3 , shown by a brown color. 

Generally shale contains some pyrite, FeS2 , and correction 

must be made for its conversion to Fe2O3 on ignition. 

If FejOs is present, weigh a portion of the residue, transfer 

to a platinum dish, fume with a mixture of nitric, perchloric, and hydrofluoric acids, dissolve in hydrochloric 

acid, and determine Fe2O3 colorimetrically. 

Calculate the percentage of organic matter in the sample 

as follows, correcting for pyrite if iron has been found in 

the residue:

Percentage of organic matter =1 00 X

10.

11

Sw

where RI= weight of residue, in grams, after drying at 

80°C; R2 = weight of residue, in grams, after ignition at 

1000°C; 0.5= loss in weight of FeS2 , in grams, when converted to 1 g of Fe2O3 ; Fe2O3 = weight of Fe2O3 in residue, 

in grams, calculated from the colorimetric determination; 

and Sw= sample weight, usually 1.0 g.

PRECISION OF ORGANIC MATTER DETERMINATIONS

Organic matter was determined in laboratory E on 

40 samples selected by H. A. Tourtebt after organic 

carbon had been reported. The other 40 samples were 

not analyzed for organic matter, because the organic 

carbon determinations indicated that the organic 

matter would probably be <0.5 percent. The concentration ranges for organic matter were 0.5 percent, 

(45 samples); from 0.5 to 5 percent (25 samples); and 

from 5 to 13 percent (10 samples). The results on 

replicate determinations are given hi table 51, those on 

the hidden splits in table 52, and those on the check 

samples in table 53.

Results of laboratory E on the check samples are 

compared with those of A in figure 19.

15

O 

cc

LU 

Q_

LU

O 

CD

<

O

z

O 

O

0

ORGANIC MATTER, IN PERCENT 

LABORATORY A

15

FIGURE 19. Comparison of organic-matter determinations of E with those of A.

TABLE 51. Replicate determinations l of organic matter, in percent, 

made in laboratory E

[Analysis by method described; Sarah Berthold, analyst. Add 259500 to all sample 

numbers except 00 to which add 259600, to form serial numbers]

36. 

00

31 

52 

77. 

60 

07

55

 0.2 0.2

______ .2 .2

 ... .4 .4

 .5 .6

 .7 .8

 .9 .8

 .9 .9

 .9 .9

_ ___ __ 1.1 1.1

43 

74 

56 

63. -

26 

82 

99. 

03 

1 Precision and reliability of determination:

Range 

05-5 -

5 -50--- 

. 1.5 1.5

 _ 2.5 2.4

 ...... ...... _ 3.1 3.2

 .... .... ...... . 3.7 3.8

 5.0 4.9

 . 8.4 8.4

 . 12.2 12.1

 12.2 12.1

Standard Number of 

deviations comparisons 

...... 0.056 11

 ... .57 3

TABLE 52. Determinations l of organic matter, in percent, in 

hidden splits by laboratory E

[Analysis by method described; Sarah Berthold, analyst. - Add 259500 to all sample 

numbers, except 00 to 05 to which add 259500, to form serial numbers. Groups 

indicate the samples that were duplicates]

33 

97 

49 

96 . 

99 

1 Precision and relia 

0.5-5-.- . 

5 -50- 

0.9

.9

12.2 

12.2

12.1

bility

53 

04 .

65 

98 

68 

01. 

of determinations: 

Range

3.5 80. 0.2

3.3 00 .2

.2 82. ____________ 8.4 

.2 02. _________ . 8.4

1.0 86. .3

1.0 05 .2

Standard Number of 

deviations comparisons 

........ 0.081 3

 .046 7
CHEMICAL ANALYSES FOR SELECTED MINOR ELEMENTS IN PIERRE SHALE A-41

TABLE 53. Determinations l of organic matter, in percent, in 

check samples

[Add 259500 to each sample number to form serial number]

Sample

28. __ - __ ........

33 .

37 . .

39. ......

46- _.....

48 . _ ..

49 

63 

92. _ ...

94- ____ ... 

E

0.9

12 2

3.8

1.3

1.2

A

<0.2

<

o

<.2

.4

1.2

12.6

4.2

1.3

1.1

Mean

O n

0.4

1.2

12 4

4.0

1.3

1.2

Difference (max 

mln)

0

0.4

.4

0

.1

Standard 

deviation

0

0.18

.18

0

no

i Precision and reliability of determinations in the range 0.5 to 5: standard deviation, 0.15; number of comparisons, 4.

E. Method described; Sarah Berthold, analyst. 

A. Method described; Edward Fennelly, analyst.

SUMMARY

Methods for the chemical determination of minor elements in Pierre shale, comprising 26 different procedures 

are given in detail. Standard deviations of the various determinations covering the predominant concentration ranges of each element are reported with the 

methods. The very narrow, low range of 1.0 to 5.0 

ppm included selenium, 50 samples; molybdenum, 33 

samples; and uranium, 48 samples. The concentration 

range 5 to 50 ppm included cobalt, 80 samples; lead, 80 

samples; copper, 57 samples; nickel, 46 samples; and 

arsenic, 64 samples. Elements predominantly in the 

range 50 to 500 ppm were vanadium, 61 samples; zinc, 

76 samples; chromium, 71 samples; and manganese, 59 

samples. All 80 samples of shale contained from 0.05 to 

0.5 percent titanium, whereas less than 2 ppm of tungsten were found in 48 of the samples analyzed .for this 

element.

Determinations and methods, for carbon and organic 

matter, are included in this report not only because of 

their importance to the study of shale but because of the 

general paucity of data for these substances in the literature. The ratio of organic matter to organic carbon in 

the shale is 1.36. The correlation of certain minor 

elements with organic matter warrants further study.

A summary of the average minor-element content of 

the check samples and the standard deviations calculated from data reported by all analysts and laboratories 

are given in table 54. The standard deviations were 

calculated, using the maximum difference in the determinations as a measure of the dispersion for a very small 

number of observations (Dixon and Massey, 1951, p. 

239). The large range of concentration covered by the 

10 selected samples point out some of the problems in 

calculating the precision.

A final summary of the precision and reliability of all 

the results for the various elements according to concentration range is given in table 55. These data are to be 

used with discretion when camparing the precisions of 

the determination of one element with those of another.

In general, duplicate determinations made by one 

analyst, or made in one laboratory, have smaller standard deviations than determinations made in different 

laboratories or with different methods. Very frequently, differences have no statistical significance. Where 

limited data were available, standard deviations were 

calculated largely to be consistent and with the attitude 

that some data are possibly better than no data at all.

TABLE 54. Mean element content and standard deviation of 10 check samples

[Standard deviation calculated according to Dixon and Massey, 1951. Mean determinations of the upper group are given in percent, those of the lower group are given in

parts per million]

Carbonate carbon.

Organic matter. . . .

Vanadium

Nickel ..

Selenium...... ....

M olybdenum ...... Uranium

2

Mean

7.7 

7.9

<-2

<-2

.15

43

70

64

4n

20

58

16

5

<1

1 

1.7

8

Standard deviation

0.24 

.30

030

.012

5.0

9.2

2.6

2.4

2.4

9 0

1.8

1.7

0 

.2

3

Mean

1.5

2.1

.6

.9

.20

3.5

200

52

15

94

33

ion

15

1 1

1

3 

1.3

3

Standard deviation

0 

0.35

.53

0

nio

.059

10

4.4

5.6

3.5

6.3

1.5

9 A

1 f\

.6

.9 

.1

3

Mean

0.09 

.2

<.2

<-2

.15

.020

20

<4

4

OQ

5

o/v\

30

<1

<1

10

7

Standard deviation

0.043 

.12

.013

0034

15

O 0

1 9

2.4

2.8

ft SI

3.0

.5

.9

3

Mean

0.07 

<-2

<

o

<

o

OE

flOQ

210

72

10

CO

27

ion

27

7

1

4 

5.6

9

Standard deviation

0.034

.022

(VUQ

15

ia

2

O

4.7

2.4

9 7

1 ft

.5

.6

2.7 

.6

4

Mean

0.04

.5

.4

.4

.38

AOQ

230

100

O1

140

38 i fin

27

10

1

2 

5.1

6

Standard deviation

0.029 

.06

0

.039

.0058

10

7.8

3 0

5 0

2.4

15

1 S

.5

.6

.9 

.2

4

Mean

<0.02 

<o

<

<)

1.2

.14

.025

12

14

72

40

9QA

31

34

6

11

2

0

8

Standard deviation

 

.013

.0024

19

9.2

3 0

3.5

2.8

34

3.0

3

e

1.8

2.7 

.3

4

Mean

<0.02 

8.4

8.4

12.4

.27

.016

Ann

130

17

66

71

no

36

AQ

110

340

8.3

9

Standard deviation

"6."i2"

.18

.18

.056

.0039

92

4.9

3.0

6.5

.8

45

15

5

12

27

.7

6

Mean

<0.02 

3.2

3.2

4.0

.44

.008

370

150

4

14

71

45

18

38

24

21 

25

3

Standard deviation

Toe"

.09

.18

.022

.0034

24

15

1.9

3.0

4.0

9.2

3.5

0

1.8

4.4 

1.5

9

Mean

<0.02 

.9

.9

1.3

.41,

.012

230

120

13

23

41

170

25

44

2

4 

10

2

Standard deviation

"6." 12"

.18

0

.017

.0034

10

15

2.2

1.2

2.4

9.7

3.0

.9

.6

2.7 

.8

9

Mean

0.66 

1.4

.8

1.2

.42

.017

220

120

9

39

27

120

23

11

2

1 

3.9

4

Standard deviation

0.01 

.12

.09

.09

.022

.0029

15

29

1.7

2.4

4.0

4.9

.6

.9

1.2

1.8 

.2
A-42 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALE 

TABLE 55. Summary of the precision and reliability of the determinations for various elements

0.00005 to 0.0005

Standard deviation

Number of comparisons

0.0005 to 0.005

Standard deviation

Number of comparisons

0.005 to 0.05

Standard deviation

Number of comparisons

0.05 to 0.5

Standard deviation

Number of comparisons

0.5 to 5

Standard deviation

Number of comparisons

5 to 50

Standard deviation

Number of comparisons

Titanium

Replicates: 

B, C-............-...._________._.______

B, D_...__._..___._______._________..___

Hidden splits: 

B.. ......... __ .......................

B, C+D. ...............................

Check samples: 

B, A....... ..........................

B.C....................................

B, D....... .............................

B.F.. ..................................

B, 0.............. ......................

All data _______________ .

0.015 

.020

.013 

.030

.024 

.025 

.008 

.051 

.058 

.029 

.026

14 

40

13

18

10 

4 

6 

10 

10 

10 

100

Vanadium

Replicates: 

A.- __ _ _ _ .....

Hidden splits:

Check samples: 

A, Au. .................................

A, Aj.. .................................

A, B. ...............................

AU data.... ...........................

0.0015 

.0019

.0016 

.0019 

.0009 

.0018

11

7

8 

8 

8 

48

0.0098

.0097 

.0032 

.0025 

.0064

6

2 

2 

2 

12

Chromium

Replicates: 

B. _________ . __ . . _ _

Hidden splits: 

B.. .....................................

Check samples: 

B, A....................................

B.F.. ..............................

B, G......_....._... ....................

0.0005 

.00034

.0008 

.0007 

.0013

8 

13

10 

10 

10

Manganese

Replicates:

A, C............... .....................

A, D.............. ......................

Hidden splits: 

A.. .....................................

A, C+D............................ .

Check samples: 

A, B. ...................................

A, C+D................................

A,F....................................

0.0014 

.0021 

.0037

.0013 

.0034

.0020 

.0031 

.0040

20 

18 

46

11 

36

8 

8 

8

0.0032 

.0050 

.0025

.0021

6 

4 

17

4

0.043 

.079 

.025

.086

3 

4 

2

4

Cobalt

Hidden splits: 

B ___________ . ___ . _____ ..

Check samples: 

B, A....................................

B,Ai.. .................................

B, F.. _ . __ ....................

B,O .................................

AU data.......... .......................

0.00010

.00043 

.00029 

.00016 

.00026 

.00031

13

10 

10 

10 

8 

92

Nickel

Replicates:

Hidden spUts:

Check samples: A, B..:.................................

A, F.. .............................

0.00012 

.00019

.00018 

.00025

19

5

5 

5

0.00035 

.00044

.00043 

.00046

26

8

5 

5
CHEMICAL ANALYSES FOB SELECTED MINOR ELEMENTS IN PIERRE SHALE 

TABLE 55. Summary of the precision and reliability of the determinations for various elements Continued

A-43

0.00005 to 0.0005

Standard deviation

Number of comparisons

0.0005 to 0.005

Standard deviation

Number of comparisons

0.005 to 0.05

Standard deviation

Number of comparisons

0.05 to 0.5

Standard deviation

Number of comparisons

0.5 to 5

Standard deviation

Number of comparisons

5 to 50

Standard deviation

Number of comparisons

Replicates: 

B... ____ . ___ .....................

Hidden splits: 

B-. _ . . ..-...._..._.....

Cbeck samples: 

B, A....................................

B, Ai-. ..... _ .......................

B, As ......

B, As...... ..........................

B, Ai-.-. ... ... . ___ ............

0.00027 

.00038

.00034 

.00029 

.00014 

.00034 

.00040

9 

5

8 

8 

8 

8 

8

0.00068 

.00080

.00020 

.00026 

.00016 

.00050 

.00011

4

8

2 

2 

2 

2 

2

Zinc

Replicates: 

B-. ............... ....... ....... _ .....

Hidden splits:

Cbeck samples: 

B, A..... ...............................

B, Ai... ................................

B.Ai.. .................................

Alldata.. _ . .........

0.0010 

.00078

.0014 

.0011 

.0020 

.0013

8 

13

10 

10 

10 

60

Lead

Replicates: 

B..... _ ... __ ........................

Hidden splits: 

B.. .....................................

Cbeck samples: 

B, A ............ ...... ..... ........

B.Ai. ...............................

All data........... ......................

0.00026 

.00053

.00060 

.00026 

.00047

13 

13

10 

10 

30

Arsenic

Replicates: 

A...... ... .............

Hidden splits: 

A.. ........... _ ..... __ ...

Cbeck samples: 

A, B- ............

All data....... __ ......................

0.000056 

.000037

.00057 

.00013

16

7

9 

37

0.00010 

.00055

.00022 

.00057

2 

6

1 

3

Selenium

Replicates:

Hidden splits: 

A- . ...... ..

Cbeck samples: A, B..:........... ........... ...........

A, Bi---. ... ...... ..............

0.000023 

.00012

.00026 

.00003

9 

5

7 

7

0.00032 

.00022

.00020 

.00016

15 

2

2 

2

0.00059 

.00050

.0021

7 

6

1 

1

Molybdenum

Replicates:

Hidden splits

Cbeck samples: 

A, B.....-..... ...... ........

0.00018

.00029

12

2

0.0016 

.00095

6

7

Uranium

Replicates: 

B, Bi. ................................

Hidden splits: 

B......... .. _ .........................

B.............. .........................

B, B,. ....... ...........................

Cbeck samples:

0.000022

000040

.000022

.000010

.000015

ftftnni ft

33

5

5

10

4

24

0.000058

000090

rwv\ofl

.000015

nnnni9

000081

21

36
A-44 ANALYTICAL METHODS IN GEOCHEMICAL INVESTIGATIONS OF THE PIERRE SHALE

TABLE 55. Summary of the precision and reliability of the determinations for various elements Continued

0.00005 to 0.0005

Standard deviation

Number of comparisons

0.0005 to 0.005

Standard deviation

Number of comparisons

0.005 to 0.05

Standard deviation

Number of comparisons

0.05 to 0.5

Standard deviation

Number of comparisons

0.5 to 5

Standard deviation

Number of comparisons

5 to 50

Standard deviation

Number of comparisons

Carbonate carbon

Replicates:

A, C-.-..- .. .- . ..-....

A, D_.. .................................

Hidden splits:

A, O . .......... ............. ........ .

A, D_.__...._.___. _____________ .........

Check samples: 

A, A....................................

A, C+D._ ..............................

0.014

.016

.034

.0024

.012

.028

.048

.048

7

3

99

3

6

6

2

2

0.011

.036

.14

.005

.008

.005

.005

.010

4

7

5

3

6

6

2

2

Total carbon

Replicates:

Hidden splits: 

A... - .

Ckeck samples: 

All data........... ...................

0. 056

.018

8

2

0.16

.048

.17

.24

42

3

17

9

0.57

.20

20

8

Organic carbon

Replicates:

Hidden splits: 

A.......................................

Check samples: 

A, Ai. ..... . . ... 

0.093

.12

3

4

0.12

.11

.10

13

2

3

0.34

.25

3

7

Organic matter

Replicates: 

E.... ____ . _ .......... _ .... ......

Hidden splits: 

E... ...... ..............................

Check samples: 

E, A....................................

0.056

.081

.15

11

3

4

0.057

.046

3

7

NOTE. See table giving determinations of respective element for explanation of letter symbols.

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