Rapid Analysis of 

Silicate Rocks

GEOLOGICAL SURVEY BULLETIN 1036-C

Revised from Circular 165
Rapid Analysis of 

Silicate Rocks

By LEONARD SHAPIRO and W. W. BRANNOCK

A CONTRIBUTION TO GEOCHEMISTRY

GEOLOGICAL SURVEY BULLETIN 1036-C

Revised from Circular 165

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1956
UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

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

Washington 25, D. C. - Price 20 cents (paper cover)
CONTENTS

Page

Abstract______ ____-_-_-_-__ __-___-_-___.t _-__-_----__---_-_--_--___ 19

Introduction._____-____-__-----_____-_--____________--____-_____-_ 19

Apparatus and instruments___________________________.__.__________ 22

Water-repellent coated pipets___________________________________ 22

Spectrophotometer__ _ ________________________________________ 23

Flame photometer._______--_____--______-_---_-_---_-_-_-_-_-_ 24

Automatic photometric titration apparatus _______________________ 26

Carbonate tube___ ____________________________________________ 30

Preparation of sample solutions-____________________________________ 31

Discussion.___________________________________________________ 31

Reagents._ ___________-__--_--_--.-__--___-_____-_____-_-_-_-_ 32

Solution A____________-_-___-_________-____--___._-_____ 32

Solution B_____________--____-__-__--___-_-_-_._________ 32

Methods. ____________________________________________ 33

SiO2 _________________________________________________________ 33

Al2O3 ___________-________--__________--___-_-___-_____-.______ 34

Total iron as Fe2O3_--_--_----------_-----------------_-_____ 35

TiO2 ____-.___________________________________________________ 36

PjO«____.__________-________ _____________-_-----_-___---___-_ 37

MnO___._-________-_____-_-___________--_-_--__-_-_-_---____- 38

CaO___-_-___-___________-___-___-_______-_---_-__--_-_____-- 39

MgO-__-__ ______ __-__-- _- __- _-_-_ __----_-- _-- 41

K2Oand Na,O____ -_ - _---_- __ -- -_---_-__-__ 43

FeO_________________________________________________________ 45

H2O_________________________________________________________ 45

CO2 __________________________________________________________ 46

Experimental results.___________________-__-__-_--.-----_-_---_-_-- 48

References cited,________________________..-______-_-_--___-_-__-__- 49

ILLUSTRATIONS

Page 

FIGURE 4. Flow diagram for rapid analysis of silicate rocks.____________ 21

5. Cell and cell adapter for the spectrophotometer-____________ 23

6. Special glass atomizer for the flame photometer.____________ 25

7. Titration assembly,_____________________________________ 27

8. Titrator front removed_______________-_-_---_-_-_-___-_ 29

9. Circuitry of titrator_____-_-__-____--___-______--_----_--_ 30

10. Carbonate tube___-----_-----_---_-_-_-__------_-----__- 31

11. Titration curve_________________-______-____-_----_-__- 40

12. Water tube being heated on a support-____________________ 47

m
IV CONTENTS

TABLES

Page 

TABLE 1. Conversion of percent transmission (T) to absorbance (A)_____ 50

2. Concentration ranges of test samples.______________________ 51

3. Results obtained for National Bureau of Standards mixture

samples.______________________________________________ 52

4- Results obtained for two National Bureau of Standards standard

clay samples__--_---_---------------------------------- 55

5. Comparison of results obtained by rapid and conventional

analysis of two carefully studied rock samples _________ 56
A CONTRIBUTION TO GEOCHEMISTRY

RAPID ANALYSIS OF SILICATE ROCKS

By LEONARD SHAPIBO and W. W. BRANNOCK

ABSTRACT

Rapid methods are described for the determination of the major constituents 

in silicate rocks. Silica and alumina are determined spectrophotometrically on 

aliquots of a solution prepared by fusion of the sample with NaOH; a molybdenum 

blue method is used for Si02 ; and alizarin red-S is used in the determination of 

A12 03. A second solution prepared by digestion of the sample with HF and H2S04 

is used for the determination of TiOj, total iron, MriO, and P2 0s, by spectrophotometric methods. Ti02 is determined with tiron, total iron with orthophenanthroline, MnO as the permanganate, and P2 0s as molybdivanadophosphorie acid. 

Additional aliquots of the second solution are taken to determine CaO and MgO 

with an automatic photometric titrator using Versene (disodium ethylenediamine 

tetraacetate), the CaO being first precipitated before titrating the MgO. Another 

aliquot of the same solution is used for the determination of K2 0 and Na2 0 by 

flame photometer. FeO is determined by titration with K2Cr2 0? after decomposition of a separate portion of sample with HF and HaSO*. Total H2O is 

determined by a modified Penfield method, and C02 is determined by measuring 

the volume of gas released by boiling a portion of sample powder with acid. 

Results of rapid analysis of twelve synthetic mixtures, two National Bureau of 

Standards standard samples, and two carefully studied silicate rocks are compared with the reported values.

INTRODUCTION

The greatly expanded program of the Geological Survey, following 

World War II, was accompanied by a greatly increased need for 

chemical analysis of rocks and other geological materials. At that 

time sufficient personnel and laboratory facilities were not available, 

or practicably obtainable to keep pace with the growing need.

The classical methods of rock analysis, essentially unchanged since 

they were described by Hillebrand (1900) are by their nature slow 

and complicated. They cannot readily be adapted for rapid analysis 

of large numbers of samples, and they must be used by highly skilled 

analysts.

For many geological problems approximate analyses are suitable. 

Accordingly a program of research was begun in 1950 aimed at the 

development of economical methods for making approximate analyses.

19
20 CONTRIBUTIONS TO GEOCHEMISTRY

The first satisfactory scheme developed was for the rapid analysis of 

silicate rocks. It is described in U. S. Geological Survey Circular 165 

(Shapiro and Brannock, 1952).

Application of the procedures in day to day analysis of a large number 

of rock samples indicated that it might be possible to improve and 

expand the methods of the original scheme of analysis so that by 

duplicate analyses results could be obtained at a rapid rate, which 

would be as accurate as those usually reported for analyses by classical 

methods. The procedures have been improved and expanded by 

refinement of the original ones as well as by substitution and addition 

of new ones. The present state of these methods for silicate rocks is 

described in this bulletin. The scheme described here provides for 

the determination of SiO2 , A12O3, Fe2O3, FeO, MgO, CaO, Na20, 

K2O, TiO2, P2O5, MnO, H2O, and C02 , the constituents commonly 

determined in silicate rocks. From 1951 to March 1955, 952 samples 

of silicate rocks have been analyzed by these rapid procedures. In 

addition, the procedures have been modified in various ways for the 

analysis of 871 samples of nonsilicate rocks in the same period.

The methods are rapid, simple, direct, and are less subjective than 

conventional methods. They can be easily learned and carried out 

by analysts with considerably less training than that required for 

analysis by classical methods. The rate of production for complete 

analyses can be as much as 7 times that of the conventional methods 

or, if done in duplicate, results of comparable accuracy can be obtained 

at a rate of 2 to 3 times that of the conventional methods.

There are several inherent advantages. The determination of all of 

the constituents except two are direct and are not based on quantitative 

separations or corrections. For example when MgO is determined 

an aliquot is taken from a stock solution of the sample and just this 

single constituent is run. In contrast, when conventional procedures 

are used, a long series of careful separations must be made. The two 

cases in which there remains some dependence on other determinations 

are ferric oxide and alumina. The Fe2O3 result is based on the 

difference between total iron and FeO as it is in the conventional 

methods. The A1203 value requires only a small correction based on 

the TiO2 concentration in the sample.

By virtue of the independence of the individual determinations a 

summation of the results by rapid analysis has more significance than 

a summation in conventional procedures. With conventional procedures a constituent may be incompletely precipitated at one stage 

and subsequently precipitated with another constituent and yet 

provide a good summation.

The methods described, with appropriate modifications, have been 

used in the analysis of numerous samples of diverse materials such as
RAPID ANALYSIS OF SILICATE ROCKS 21

salines, waters, iron ores, bauxites, chromites, alunites, and carbonate 

rocks.

For the sake of simplicity, the procedures for the preparation of 

sample solutions and for the various determinations describe the 

analysis of a single sample. Large numbers of samples can be most 

efficiently analyzed in batches of ten to twenty samples at a time.

Sample 

NaOH

FezOs-f VOrthophenanthroline 

CaO

PPt / Automatic

photometric titrator

Flame photometer

K2Cr20

FeO H20 C02

FIOUEE 4. Flow diagram for rapid analysis of silicate rocks.
22 CONTRIBUTIONS TO GEOCHEMISTRY

The actual number of samples per batch should be based on the amount 

of apparatus available. Unless specific instruction to the contrary is 

given, the operation described for each step in a procedure should be 

completed for all the samples in a batch before proceeding with subsequent steps.

APPARATUS AND INSTRUMENTS

Most of the apparatus used in the procedures described is available 

in laboratories making silicate rock analyses. In addition to commonplace items such as beakers, volumetric flasks, Pyrex bottles, burets, 

pipets, funnels, analytical balance, and filter paper, several more 

specialized types of apparatus are needed. They are a spectrophotometer, a flame photometer, an automatic photometric titrator, 

and a carbonate tube.

; In the preparation of solutions for determination of SiO2 and 

AJkOa, the samples are fused in covered nickel crucibles of approximately 75-ml capacity.

Platinum crucibles of about 100 ml, with covers, are used in the 

preparation of the solution (solution B) from which aliquots are taken 

for the determination of total iron, TiO2 , P2O6, MnO, CaO, MgO, 

K2O, and Na^O. These crucibles are also used in the determination 

ofFeO.

WATBB-BBPELLANT COATED PIPETS

The use of water-repellent coated pipets makes possible a substantial 

saving of time. Rinsing between samples is eliminated as coated 

pipets retain only negligible quantities of liquid. With a coated 

pipet, aliquots from 20 samples (without intermediate rinsing) are 

made easily in 5 minutes. The precision is at least as good as for 

conventional pipets, but as the accuracy may be slightly off it is 

necessary to pipet both the samples and the standard with the same 

pipet, or to use pipets known to deliver essentially equal volumes of 

solution.

Delivery tune can be as little as 6 to 10 seconds without loss of 

accuracy. Pipets for all uses except those involving strongly alkaline 

solutions should be treated as follows: Cut approximately %* in. 

from the tip of a regular transfer pipet and carefully fire-polish the cut 

edge slightly to round the edges. Allow the pipet to cool and check 

the delivery tune which should be between 6 and 10 seconds, regardless 

of pipet capacity. If necessary, fire-polish a little more, or dip the 

tip into HF solution for a few minutes depending on whether the delivery time is more than 10 seconds or less than 6 seconds. Recheck 

and repeat until within this range. Clean the pipets thoroughly 

in cleaning solution and rinse well with water. Allow to dry thoroughly.
RAPID ANALYSIS OF SILICATE ROCKS 23

Coat the pipet with water-repellent according to the directions of 

the manufacturer. Dimethyl dichlorosilane is very convenient to 

use as it is necessary only to flow it in and out of the clean pipet, 

then allowed to dry.

SPECTROPHOTOMETER

All spectrophotometric measurements were made with a Beckman 

model B spectrophotometer. Nevertheless, the methods can readily 

be adapted to use other good quality spectrophotometers. Only one 

phototube was employed for the measurements, all of which were 

made in the range 320-700 m/z.

To insure the stability of the source of illumination a storage 

battery was used. The amplifier circuit of the instrument was fed by 

an a-c line. In place of a set of large matched test tubes previously 

used as absorption tubes, a single fixed tube with a drain at the bottom 

was found more satisfactory.

The simple adapter, shown in figure 5, was built to hold the absorption cell, in a fixed position in the cell compartment. Care must 

be taken to insure that the adapter and cell compartment are rigidly

Absorption tube, glass

32

All joints butt-soldered 

Pinch clampFace plate of 

spectrophotometer

Rubber tube

FIOUEB 5. Cell and cell adapter for the spectrophotometer.
24 CONTRIBUTIONS TO GEOCHEMISTRY

fixed in position in order to maintain a constant light path. The 

absorption cell should be treated with a water-repellent to eliminate 

the necessity of rinsing between additions of solutions. The-spectrophotometer must be raised on a platform approximately 5 in. to allow 

access to the absorption tube outlet.

The spectrophotometer is operated as follows: After the instrument 

has been allowed to warm up for about 20 minutes, pour at least 25 ml 

of the reference blank solution into the absorption cell, taking care to 

avoid the formation of bubbles on the cell walls. This can be done 

simply by using a water-repellent treated funnel with a short stem 

bent at an angle so that the tip touches the side of the absorption cell. 

Set the wave length selector to the desired wave length, adjust the 

"dark current" reading to zero, set the sensitivity switch to position 1, 

open the phototube shutter and adjust the meter to read 100 percent 

transmittance by varying the slit width. Close the shutter and allow 

the reference blank solution to drain from the absorption cell back into 

the original container. Carefully pour at least 25 ml of sample solution 

into the absorption cell. Open the shutter and observe the meter 

reading. If the percent transmittance reading is less than 31.5 percent, turn the sensitivity switch to a position which gives a reading 

greater than 31.5 and record the meter reading and sensitivity setting. 

Should the reading still be less than 31.5 percent after turning the 

sensitivity switch to position 4, the reading at position 4 is used. It 

is preferable to make the readings on the percent transmittance scale 

rather than the absorbance scale because readings made on the percent 

transmittance scale, which is graduated uniformly, are less subject 

to error.

For those determinations in which the spectrophotometer is used, 

percent transmittance readings are first converted to absorbance by 

interpolation of the values in table 1 (p. 50) which was derived by the 

use of the equation: A (absorbance) = 2 log T (transmittance). All 

calculations are then made with the absorbance values. Absorbance 

values are easier to use in making calculations than percent transmittance values because, when Beer's Law is followed, the absorbance 

is proportional to the concentration of the constituent imparting the 

color to the solution being analyzed and percent transmittance is not.

FLAME PHOTOMETER

The procedures described for the determination of Na^O and K^O 

have been worked out specifically for the Perkin-Elmer Model 52C 

flame photometer. Other types of flame photometers can be substituted for this instrument if the characteristics of a particular instrument are studied, and specific procedures are devised.

When the Model 52C flame photometer is used it is set up as suggested in the instruction manual, except for several minor changes.
RAPID ANALYSIS OF SILICATE ROCKS 25

A special glass atomizer, shown in figure 6, is substituted for the 

atomizer furnished by the manufacturer, and two pressure regulators 

are installed in series between the propane supply and the instrument. 

The capillary aspirator type of atomizer shown has certain advantages over the funnel-type atomizer when used with the flame photometer in the determination of Na2O and K2O in silicate rocks. It atomizes solution into the flame at the relatively slow fixed rate of 

approximately 4 ml per minute so that a maximum of approximately 

10 ml of each sample and standard solution is consumed for each 

complete determination. This atomizer draws solution up through

Avoid enlarging ID of 

capillary at this joint

Tube for air 

(capillary or regular tubing) Tube for liquid 

(capillary tubing)

ID3mm±.25mm

eo

<M

3cm

r Fire polished

Orifice 1.0mm±.2mm 

Orifice .20mm ±.02mm 

OD at tip l-2mm

Tip beveled and 

fine-ground

FIOTTOE 6. Special glass atomizer for the flame photometer.
26 CONTRIBUTIONS TO GEOCHEMISTRY

the capillary intake tube from a small beaker. When the beaker is 

withdrawn, the capillary tube empties in a moment. The outside of 

the tube can then be wiped clean with a piece of lintless tissue, another 

solution can be passed in, and almost immediately the capillary is 

flushed clean of the previous solution. There is no waiting for solutions to clear, and the deliberate rinsing and flushing, needed in using 

the funnel type of atomizer, is unnecessary.

Two pressure regulators, installed in the gas line, produce a relatively steady burner flame by reducing fluctuations in the gas pressure.

To start the operation of the flame photometer for the determination 

of Na^O and K2O, first turn the electric switch on the panel of the 

instrument to the "on" position. Then adjust the air pressure to 10 

pounds per square inch, open the main valve on the propane tank, 

set the gas regulator which is nearest the main valve to 10 pounds 

per square inch, and allow propane to pass to the burner by opening the 

valve on the second regulator. Light the burner and adjust the 

pressure, using the second gas valve, so that the flame is steady and 

blue with small sharply defined bright blue inner cones, which do not 

jump irregularly from the burner grid. The burner chimney should 

be shifted until the flame passes up through its center. The instrument 

is then allowed to warm up for about 30 minutes before readings are 

taken.

AUTOMATIC PHOTOMETRIC TITRATION APPARATUS

The methods described in Circular 165 for the determination of 

CaO and MgO in silicate rocks by Versene (disodium ethylenediamine 

tetraacetate) titrations have been successfully used by many analysts, 

nevertheless some analysts have had difficulty in discerning titration 

end points. These difficulties have been overcome by the use of an 

automatic photometric titration apparatus, shown in figure 7. With 

this apparatus Versene is allowed to flow at a constant rate into the 

magnetically stirred solution containing the calcium or magnesium 

and appropriate reagents, in a beaker within the photometer. As the 

titration proceeds the pen-and-ink recorder plots the effect of the 

change in absorption, as the result of the color change of the solution, 

on a chart. The end point is taken as the position on the recorder 

chart at which change in absorption ceases. By comparing the time 

in seconds taken for the titration of a solution containing a known 

amount of calcium or magnesium with the time taken for the titration 

of a sample solution the amount of calcium or magnesium in the 

sample can be calculated.

The spectrophotometer used in the rest of the work can be adapted 

with an interchangeable unit to carry the titration vessel, described 

below, by removal of the plate below the cell compartment of the 

spectrophotometer. The pen-and-ink recorder described below can
RAPID ANALYSIS OF SILICATE ROCKS 27

be connected to pins 11 and 13 at the rear of the instrument. If this 

is done the titrator is replaced by the spectrophotometer, all other 

circuitry remaining the same. However, where there is a substantial 

amount of work it is more convenient to have a separate apparatus for 

CaO and MgO leaving the spectrophotometer available for other 

work. An inexpensive titrator was designed and built for the purpose 

along the lines suggested by Barredo and Taylor (1947). The entire 

set-up is as follows (see fig. 7).

Pressure-equalizer tube^ 

Air-inlet tube 

 Down-flow tube

Electromagnetic 

hosecock

RECORDER TITRATOR

FIOTJBE 7. TItration assembly.
28 CONTRIBUTIONS TO GEOCHEMISTRY

A Mariotte bottle provides a simple means for delivery of Versene 

solution to a titration beaker at a constant flow rate. A 20-liter 

bottle is mounted on a shelf or support about 4 feet above the work 

bench. It is fitted with a rubber stopper through which pass three 

glass tubes. The air inlet tube starts at a point near the bottom of 

the bottle, goes through the stopper, and opens into the air. The 

pressure equalizer tube starts in the air space above the liquid, goes 

through the stopper, and is connected to a vacuum line. Somewhere 

along this tube is placed a rubber section with a pinchcock so that 

vacuum may be applied or shut off conveniently. The downflow 

tube starts close to the bottom of the bottle, passes through the stopper, and down to the electromagnetic hosecock which is part of the 

titrator. A few inches below the electromagnetic hosecock extends 

a capillary tube with a tip so constricted that the flow rate is maintained at 4 to 5 ml per minute.

By this arrangement when liquid is flowing through the downflow 

tube the hydrostatic head is from the bottom of the air inlet tube 

(essentially the bottom of the bottle) to the top of the liquid in the 

beaker which is in the titrator. A constant head will be maintained 

as the liquid in the bottle is used up so long as the air pressure within 

the bottle is such that, as liquid is flowing out, air is entering through 

the air inlet and bubbling through the Versene solution. If the temperature in the room changes from day to day it may be necessary to 

reduce the air pressure above the liquid before the titrator is used. 

Vacuum is applied until air starts to bubble through the Versene 

solution and then the vacuum is turned off. The rubber stopper must, 

of course, provide an airtight seal to maintain the slight vacuum.

A pen-and-ink recorder which provides full scale deflection for 1 

milliampere is used. It should have an internal resistance not exceeding 2,000 ohms. The chart drive should be geared to a feed of 

about 3 inches per minute at a constant rate.

The titrator shown in figure 7 is ready to use and in figure 8 the 

front panel is removed. The wiring diagram is given in figure 9. 

There are four simple circuits: the stirrer circuit (a), the titrate 

circuit (b), the light circuit (c), and the photocell circuit (d). The 

stirrer circuit consists merely of a magnetic stirrer with an on-off 

switch connected directly to the line current. The titrate circuit is a 

double-throw single-pole switch which is connected in such a way that 

line current is allowed to go either to the electromagnetic hosecock, 

or, when thrown to the opposite position, to the chart drive of the 

recorder. By this means coordination is achieved between the opening of the hosecock, which starts the flow of Versene, and the start of 

movement of the chart. The light circuit is fed from the line, through 

a voltage stabilizer, to the primary of a 6- 8-volt transformer. The
RAPID ANALYSIS OF SILICATE ROCKS 29

secondary of the transformer is in series with a 50-candlepower automobile light bulb and a 50-watt 5-ohm rheostat.

The photocell circuit is a series circuit involving a barrier layer 

selenium photocell, a l^-volt dry-cell battery, and the galvanometer 

of the recorder. In this application, advantage is taken of the decrease 

in resistance of the photocell as the light intensity is increased rather 

than the output of the photocell itself. The polarity of the units 

must be correct, as shown in the diagram, or the circuit will not 

function. A few minutes of experimenting at this point will yield 

the proper arrangement. A carrier for two 2-in. by 2-in. niters is

Electromagnetic 

hosecock

Collimating lenses 

Reflector

Photocell with 

mountings for two 2" x 2" 

glass filters

I

6-8 volt 

transformer

FIGURE 8. Titrator, front removed.
30 CONTRIBUTIONS TO GEOCHEMISTRY

Electromagnetic 

hosecock

B-Titrate circuit

50 cp bulb

Voltage stabilizer

C-Light circuit

Photocell

Recorder pen 

L5v movement

D-Photocell circuit

FIOUEK 9. Circuitry of titrator.

mounted in front of the photocell. An orange filter (Corning 3480) 

is used in titrating MgO, and this plus a green filter (Corning 4015) 

are used in titrating CaO.

It is desirable to have several 400-ml tall-form beakers, with lines 

marked off about 3% inches from the bottom of the beaker so that the 

same hydrostatic head is maintained from the bottom of the air inlet 

tube to the surface of the liquid, from beaker to beaker.

CARBONATE TUBE

The carbonate tube is a simple device designed to catch and measure 

the CO2 evolved from a sample upon treatment with acid. It consists 

of an 18 mm by 150 mm test tube with a side arm attached as shown 

in figure 10.
RAPID ANALYSIS OF SILICATE BOCKS 31

Test tube 18 x 150mm

Oil level 

mark

10. Carbonate tube.

PREPARATION OF SAMPLE SOLUTIONS 

DISCUSSION

The major part of the analysis is made on two solutions, which are 

designated solution A and solution B. (See fig. 4.)

Solution A is used in the determination of Si02 and A1203 . It is 

prepared by fusing approximately 0.0500 g of the sample with NaOH 

in a nickel crucible. In this way decomposition is obtained very 

quickly and at a comparatively low temperature. The nickel crucible 

is only slightly attacked, and the nickel taken into solution does not 

interfere with the subsequent determinations of Si02 and A1203.

Two reference standard solutions and a reference blank solution 

are prepared simultaneously with solution A. National Bureau of 

Standards standard sample no. 99 (feldspar) is used in the preparation 

of the reference standard solutions. The reference blank solution is 

prepared in the same way as solution A except that sample powder is 

omitted.

355887 55 3
32 CONTRIBUTIONS TO GEOCHEMISTRY

Solution B is used in the determinations of TiO2 , total iron, MnO, 

P2O5} MgO, CaO, Na2O, and K2O. To prepare this solution, a 0.400 

g sample is digested overnight with HF and H2SO4 in a large covered 

platinum crucible on a steam bath. HF is then removed by heating 

until copious fumes of SO3 are given off, and the residue is dissolved 

in water and made to volume.

To minimize contamination from glass, the aliquots of solution B 

used for determining Na2O and K2O should be withdrawn immediately 

after preparation of the solution. Na2O and K2O should then be 

determined immediately, or the aliquots should be stored in plastic 

bottles.

REAGENTS

NaOH solution, 15 percent: Prepare 1 liter and store in a plastic bottle. 

HF, 48 percent. 

H2SO4, concentrated.

SOLUTION A

1. Transfer 10 ml of NaOH solution, measured with a plastic graduated cylinder, to a nickel crucible of about 75-ml capacity. (The crucible should be cleaned 

with dilute HC1 before using.)

2. Transfer 10 ml of NaOH to each of three additional clean nickel crucibles 

for preparation of two reference standard solutions and a reference blank solution.

3. Evaporate the solutions to dryness over gas burners or electric heaters. A 

slight amount of spattering can be ignored.

4. Accurately weigh (to the nearest 0.1 mg) approximately 0.0500 g of sample 

powder (ground to pass a 100-mesh screen) and two portions of National Bureau 

of Standards standard sample no. 99. Transfer each portion of powder to an 

individual crucible containing NaOH. Exactly 0.0500-g sample portions can be 

weighed if desired. In this way the ultimate calculation of percent SiO2 and 

percent Al2Os can be simplified, but in so doing the total time required for the 

determinations may be increased appreciably.

5. Cover and heat all of the crucibles to dull redness for about 5 minutes. 

Remove each crucible from the heat and swirl the melt around the sides. Allow 

the melts to cool.

6. Add approximately 50 ml of water to each crucible, cover, and allow to 

stand overnight.

7. Transfer the contents of the crucibles to beakers containing about 400 ml of 

distilled water and 20 ml of 1 +1 HC1. Scrub each crucible with a rubber policeman and wash any remaining solution or residue into the appropriate beaker. 

(Do not allow the nickel crucibles to come in contact with the acid solutions.)

8. Transfer the solutions to individual 1-liter volumetric flasks, dilute to 1 liter 

with distilled water, and mix well. (The flasks should be cleaned with 1+1 HC1 

before use.)

SOLUTION B

1. Transfer a 0.400-g sample to a platinum crucible of about 100-ml capacity.

2. Add 10 ml of HF.

3. Add 3 ml of H2SO4.

4. Cover the crucible with a platinum cover and digest overnight on a steam 

bath.

5. Remove the cover, allow the crucible to heat on the steam bath until thevolume of liquid is reduced to about 3 ml, and add about 1 ml of
RAPID ANALYSIS OF SILICATE ROCKS 33

6. Place the crucible over an electric heater or gas burner and heat until strong 

80s fumes evolve.

7. Allow the crucible and contents to cool.

8. Pill the crucible with distilled water, cover, and digest on the steam bath 

until the residue dissolves. If a residue remains after digesting for about half an 

hour, transfer solution and residue to a 400-ml Vycor beaker and boil gently for 

10 to 15 minutes. If a small insoluble residue remains, it may be barium sulfate, 

zircon, or possibly tourmaline. This may be filtered off and discarded because 

BaO and Zr02 are not determined. Tourmaline is usually not found in more 

than trivial quantities.

9. Transfer the solution to a 200-ml volumetric flask, dilute to volume, and 

mix well.

10. Immediately withdraw 25 ml of the solution with a pipet and transfer to a 

150-ml Pyrex beaker or Pyrex bottle if NazO can be determined the same day, or, if 

Na20 cannot be determined the same day, transfer the aliquot to a plastic bottle 

to eliminate the possibility of alkali contamination from the container.

METHODS

Si02

In the determination of SiO2 (Bunting, 1944) the yellow silicomolybdate complex is reduced to molybdenum blue and the transmission of light is measured at 650 m /*. As silica is the predominant 

constituent in silicate rocks, relatively more precise values are desired 

for SiOs than for the constituents present in lower concentrations. 

For this reason sample weighings, volume measurements, and spectrophotometer readings must be made very carefully.

REAGENTS

Ammonium molybdate reagent solution: Dissolve 7.5 g of ammonium molybdate

in 75 ml of water. Add 10 ml of 1+1 H2S04 and dilute to 100 ml. Store

in a plastic bottle. 

Tartaric acid solution, 10 percent: Prepare 500 ml and store in a plastic bottle.

Discard and prepare fresh solution when an appreciable amount of sediment

forms. 

Reducing solution: Dissolve 0.7 g of sodium sulfite in 10 ml of water. Add 0.15

g of l-amino-2-napthol-4-sulfonie acid and stir until dissolved. Dissolve

9 g of sodium bisulphite in 90 ml of water and add this solution to the

solution above and mix. Store in plastic bottle.

PROCEDURE

1. Withdraw 10 ml of sample solution A, 10 ml of each reference standard 

solution, and 10 ml of the solution A blank solution (see Preparation of sample 

solution, Solution A, step 8) with a pipet, and transfer each aliquot to a separate 

100-ml volumetric flask which has been cleaned with 1+1 HC1.

2. Add 1 ml of the ammonium molybdate reagent solution with a pipet, swirling the flasks during the additions. Mix well and allow to stand for 10 minutes.

3. Add 4 ml of the tartaric acid solution with a pipet, swirling the flasks while 

adding and mix well.

4. Add 1 ml of the reducing solution with a pipet, while swirling the flasks, 

dilute to volume, mix well, and allow to stand at least 30 minutes.
34 CONTRIBUTIONS TO GEOCHEMISTRY

5. Determine the percent transmission for each solution at 650 m M using the 

solution prepared from the solution A blank solution as the reference blank 

solution.

CALCULATIONS

1. Convert each of the values obtained for percent transmission to absorbance 

using table 1.

2. Calculate all of the absorbance values to a 50-mg sample-weight basis 

using the original sample weights (Solution A, step 4):

50 AbsorbanceX ; = ci=absorbance on a 50-mg sample-weight basis, sample weight or o

3. Compute a factor for each of the two comparison standards:

______Percent SiO2 of comparison standard______. ,

Absorbance of comparison standard (on 50-mg basis)

4. Calculate an average from the two factors.

5. Compute the percent SiO2 in the sample:

(Average factor) X (absorbance of sample solution, on 50-mg basis) = per cent SiOa

A12O3

Alumina (A12O3) is determined by measuring the transmission of 

light at 475 m M of a solution containing the complex of aluminum, 

calcium, and alizarin red-S (Parker and Goddard, 1950). This 

complex has been found to have a much greater absorption, for a 

giver amount of aluminum, than the complex formed by aluminum 

and alizarin red-S alone. Complexes, which absorb light at 475 

m n, are also formed by iron and titanium with calcium and alizarin 

red-S. The effect of iron is eliminated by the formation of ferrous 

ferricyanide prior to adding alizarin red-S solution to the sample 

solution. The effect of titanium is found empirically and a comparatively small correction, based on the determined TiO2 value, is 

subtracted from the apparent value for percent A12O3 obtained from 

the total absorption at 475 m /x.

It has been empirically determined that for each percent TiO2 

in the sample an apparent increase of 0.5 percent A12O3 results. The 

correction for TiO2 can then be made simply by subtracting one-half 

the percent of TiO2 , as determined under Determination of TiO2 , from 

the apparent percent A12O3 .

REAGENTS

Hydroxylamine hydrochloride solution, 10 percent: Prepare 500 ml.

Calcium chloride solution: Transfer approximately 7 g CaCOs to a 250-ml beaker.

Add about 50 ml of water. Add dilute HC1, dropwise, with stirring, until

the CaCO3 is dissolved. Boil the solution for 1 to 2 minutes. Cool and dilute

to about 500 ml. 

Potassium ferricyanide solution, 1 percent: Prepare 100 ml. Do not store for more

than 1 day.
RAPID ANALYSIS OF SILICATE ROCKS 35

Buffer solution: 70 g of sodium acetate and 30 ml of glacial acetic acid diluted to

500 ml with distilled water. 

Alizarin red-S solution, 0.1 percent: Prepare 500 ml.

PROCEDURE

1. Withdraw 20 ml of sample solution A, 20 ml of each reference standard solution, and 20 ml of the solution A blank solution (Preparation of sample solution, 

Solution A, step 8), with a pipet and transfer to individual 100-ml volumetric flasks 

which have been cleaned with 1+1 HCl and subsequently rinsed with water.

2. Add 1 ml of the CaCl2 solution to each of the flasks and mix.

3. Add 1 ml of the hydroxylamine hydrochloride solution to each flask and mix.

4. Add 1 ml of the potassium ferricyanide to each flask, mix, and allow to stand 

for 5 minutes.

5. Add 10 ml of the buffer solution measured with a graduate to each flask, 

mix, and allow to stand 10 minutes.

6. Add 5 ml of the alizarin red-S solution to each flask, dilute to 100 ml with 

distilled water, mix, and allow to stand for 1 to 2 hours.

7. Determine the percent transmission at 475 m ft for the sample solution and 

the two comparison standard solutions using the solution prepared from the solution A blank solution as the reference blank solution.

CALCULATIONS

1. Convert each of the values obtained for percent transmission to absorbance 

using table 1.

2. Calculate the absorbance values to a 50-mg sample-weight basis:

50 Absorbance X ; . , . , r= absorbance on a 50-mg Weight basis, sample Weight (mg)

3. Compute a factor for each of the two comparison standards:

_______Percent Al2Os of comparison standard_______ __, 

Absorbance of comparison standard (on 50 mg Weight basis)

4. Calculate an average factor from the two factors.

5. Compute the apparent percent A12O3 in the sample:

Average factor X absorbance of sample solution (on 50-mg weight basis) = apparent percent AljOa.

6. To obtain the percent AljOa in the sample, subtract the correction for TiOg 

effect:

(Apparent percent A12O3) % (percent TiO2 in the sample) =pereent A12O3.

Note: The procedure described above for the determination of A^Os tends to 

give low results for samples containing more than 20 percent A^Os. For samples 

of this type, which are rare, the difficulty can be overcome by using 10 ml of solution A plus 10 ml of solution A blank solution in the same flask, instead of the 

usual 20-ml aliquot of solution A. The 10 ml of the solution A blank solution is 

added so that the correct pH will be maintained.

TOTAL IRON AS Fe2O3

Total iron is determined by measuring the transmission of light at 

560 m M of a solution containing the orange ferrous orthophenanthroline complex (Bandemer and Schaible, 1944). This procedure is 

simple and highly reliable.
36 CONTRIBUTIONS TO GEOCHEMISTRY

REAGENTS

Hydroxylamine hydrochloride, 10 percent: Prepare 500 ml.

Orthophenathroline solution, 0.1 percent: Prepare 500 ml.

Sodium citrate solution, 10 percent: Prepare 500 ml.

Standard iron solution: Weigh 0.491 g FeSO4-(NH4) 2SO4 -6H2O and transfer to a 

500 ml volumetric flask. Add 3 ml of 1+1 H^SO* and about 300 ml of water. 

Stir until completely dissolved, then add water to the mark, and mix. The 

FegOg concentration in this solution is 0.2 mg per ml, which is equivalent to 

that in a solution prepared from a sample containing 10.00 percent Fe2Os, as 

directed under Preparation of sample solution, solution B.

PROCEDURE

1. To a set of 100-ml volumetric flasks, add nothing to the first flask (to serve 

as a blank), 5 ml of the standard iron solution to the second flask, and 5 ml of 

sample solution B to the third flask. (The aliquots should be measured with a 

pipet.)

2. Add 5 ml of the hydroxylamine hydrochloride solution to each flask with a 

graduated cylinder and allow to stand for 10 minutes.

3. Add 10 ml of the orthophenanthroline solution with a graduated cylinder.

4. Add 10 ml of the sodium citrate solution with a graduated cylinder.

5. Dilute to 100 ml with distilled water and mix.

6. After one hour determine the percent transmission at 560 m p, for the 

sample and standard solutions using the reagent blank as the reference blank 

solution.

CAI^CUIiATIONS

1. Convert each of the values obtained for percent transmission to absorbance 

using table 1.

2. Compute the factor for the standard solution:

10 -=factor.

Absorbance of the standard solution 

3. Compute percent total iron as Fe2Os :

(Factor) X (absorbance of sample solution) = percent total Fe as Fe2Os.

Note: Percent Fe2Os in the sample is calculated in the usual way by subtracting 

the Fe2 (>3 equivalent of FeO (separately determined) from the value for total 

Fe as Fe2O3 :

(Percent total Fe as Fe2Os) (percent FeO X 1.1)== percent Fe2O3 .

TiO2

To determine TiC>2 measure the transmission of light at 430 m ^ by 

solutions containing the yellow complex produced by the reaction of 

titanium with tiron (disodium-1, 2-dihydroxybenzene-3, 5-disulfonate) 

(Yoe and Armstrong, 1947).

REAGENTS

Tiron (disodium-1, 2-dihydroxybenzene-3, 5-disulfonate): Dry reagent powder. 

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

to 1 liter with distilled water. 

Sodium dithionite, Na2S2O4 (sometimes sold as sodium hydrosulphite): Dry

reagent powder.
RAPID ANALYSIS OF SILICATE ROCKS 37

Standard TiO2 solution: Weigh 0.1013 g of National Bureau of Standards standard 

sample no. 154 (titanium dioxide) or the appropriate amount of reagent 

TiO2 of known composition. Transfer to a small platinum crucible. Add 

2 g of sodium bisulphate, cover, and heat until the sample is completely 

fused. Allow to cool and place the crucible into a beaker containing 50 ml 

of 1+1 H2SC>4. Heat and stir until the melt is completely dissolved. Cool, 

dilute the solution to 250 ml in a volumetric flask, and mix well. Transfer 

50 ml of the solution with a pipet to a 1-liter volumetric flask, dilute to the 

mark, and mix. Store the solution in a glass-stoppered bottle. The concentration of Ti02 is 0.02 mg per ml which is equivalent to that in a solution 

prepared from a sample containing 1.00 percent TiO2, as directed under 

Preparation of sample solution, solution B.

PROCEDURE

1. To the first of a series of dry 100-ml beakers add 5 ml of water, to the second 

add 5 ml of the standard TiO2 solution, and to the third add 5 ml of sample solution 

B. Use a pipet for the measurements.

2. With a small scoop add about 130 mg of dry tiron powder to each beaker.

3. With a pipet add 50 ml of the buffer solution to each solution and mix.

4. Set the spectrophotometer to 430 m /*. Add about 10 to 20 mg of sodium 

dithionite powder to the solution to be used as a reagent blank solution and mix 

gently by rotating the beaker two or three times. Do not overmix.

5. After about 1 minute pour the solution into the absorption cell and adjust 

the slit width to give 100 percent transmission.

6. Repeat with each solution, adding dithionite, waiting about 1 minute, and 

reading percent transmission.

CALCULATIONS

1. Convert each of the values obtained for percent transmission to absorbance 

using table 1.

2. Compute the factor for the standard solution:

- = factor. Absorbance of standard solution 

3. Compute percent TiO2 :

(Factor) X (absorbance of sample solution) = percent TiO2.

P2 06

The phosphate content of a sample is determined by measuring the 

light transmitted at 430 m p by a solution containing the yellow 

molybdivanadophosphoric acid complex (Kitson and Mellon, 1944).

REAGENTS

Molybdivanadate solution: Dissolve 1.25 g of ammonium metavanadate in 400 ml 

of 1+1 HNOj. Dissolve 50 g of ammonium molybdate in 400 ml of water. 

Mix the solutions and make up to 1 liter with water.

Standard PzOg solution: Transfer 0.0849 g of National Bureau of Standards 

standard phosphate rock no. 120 to a 150-ml beaker and add 25 ml of 1 + 1 

HNOj. Digest on a steam bath until solution is essentially complete. 

Cool and make up to 2 liters in a volumetric flask. Store in a glass-stoppered 

bottle. The concentration of P2C>6 is 0.015 mg per ml which is equivalent to 

that in a solution prepared from a sample containing 0.75 percent PaOg as 

directed under Preparation of sample solution, solution B.
38 CONTRIBUTIONS TO GEOCHEMISTRY

PROCEDURE

1. With a pipet transfer a 15-ml aliquot of sample solution B to a 100-ml 

beaker. At the same time transfer 15 ml of water and 15 ml of the standard 

solution to two additional beakers, for a blank and standard.

2. Add 10 ml of the molybdivanadate solution to each solution with a pipet, 

swirling the solutions during the additions. Add 25 ml of water with a pipet, 

mix. and allow to stand for at least 5 minutes.

3. Determine the percent transmission, at 430 m /* for each solution using the 

reagent blank solution as the reference blank solution.

CALCULATIONS

1. Convert the readings for percent transmission to absorbance using table 1.

2. Compute a factor:

0.75 , ,

 = factor. Absorbance of standard solution 

3. Calculate percent PjOj:

(Factor) X (absorbance of sample solution) = percent PjOg.

MnO

Manganese oxide is determined by measuring the light transmitted 

at 525 m /* by a sample solution in which the manganese has been 

oxidized to permanganate with KIO* (Willard and Greathouse, 1917).

REAGENTS

KI04: Dry powder.

Acid mixture: Water solution containing 10 percent H8P04 and 25 percent 

H2SO4 by volume, 2 liters.

Standard MnO solution: Transfer 0.0531 g of National Bureau of Standards 

standard sample no 25b (manganese ore) to a 250-ml beaker. Add 25 ml of 

1 + 1 HN03 and 2 to 3 ml of 3 percent H2 02. Digest on a steam bath until 

no black residue remains. Cool and add 50 ml of HaSO*. Evaporate and 

continue heating until fumes of SOs are evolved. Cool and dilute to approximately 200-ml volume. If necessary warm to dissolve. Cool and dilute 

to 2 liters. Store in glass-stoppered bottle. The MnO content is 0.02 mg 

per ml which is equal to that in a solution prepared from a sample containing 

1.0 percent MnO as directed under Preparation of sample solution, solution B.

PROCEDURE

1. Transfer a 20-ml aliquot of solution B to a 250-ml beaker. To two additional beakers transfer 20 ml of water and 20 ml of standard MnO solution to 

serve as a reagent blank solution and standard solution.

2. Add 50 ml of acid mixture.

3. Add approximately 0.2 g of KI04.

4. Cover the beakers, and bring to a boil. Keep at the boiling point for 5 

minutes.

5. Cool the solutions to room temperature in a water bath.

6. Transfer the solutions to 100-ml volumetric flasks, dilute to volume and 

mix well.

7. Measure the percent transmission at 525 m /* using the reagent blank solution 

as the reference.
RAPID ANALYSIS OF SILICATE ROCKS 39 

CALCULATIONS

1. Convert each of the values for percent transmission to absorbance using 

table 1.

2. Compute the factor:

__________LO__________

Absorbance of the standard solution

3. Calculate percent MnO:

(Factor) X (absorbance of sample solution) = percent MnO.

CaO

Calcium oxide is determined by titration with disodium ethylenediamine tetraacetate (Versene) using murexide (ammonium pupurate) 

as an indicator (Betz and Noll, 1950). Iron and aluminum are 

complexed with sodium potassium tartrate and do not interfere. 

The titration is carried out automatically; the change in color of the 

indicator solution is recorded with a pen-and-ink recorder as the 

titration proceeds. The apparatus used is described under Apparatus 

and instruments.

REAGENTS

Versene solution: Dissolve 20 g of disodium ethylenediamine tetraacetate in

20 liters of water and transfer to the Mariotte bottle. 

NaOH solution, 15 percent: Prepare 1 liter and store in a plastic bottle. 

Murexide indicator solution approximately 0.2 percent: Prepare 50 ml.

This solution should not be kept for more than three days. 

Sodium potassium tartrate, 20 percent: Prepare 500 ml. 

Standard CaO solution: Transfer 1.000 g of Bureau of Standards standard

sample no. 88 (dolomite) to a 250-ml beaker. Add 20 ml of HC1 1 + 1, 

cover, and boil 3 to 5 minutes. Cool to room temperature and dilute to 1 liter 

in a volumetric flask. The solution contains the equivalent of 0.305 mg of CaO 

per ml. Store the solution in a plastic bottle.

PROCEDURE

1. Transfer 1 ml of the standard CaO solution to a 400-ml tall form titration 

beaker.

2. Fill the beaker to the mark with distilled water.

3. Place the titration vessel into the titrator in position for titration, add a 

plastic coated magnet, and start the stirrer.

4. Add 3 ml of the sodium potassium tartrate solution.

5. Add 10 ml of the NaOH solution.

6. Add 1 ml of the murexide indicator solution.

7. Insert the delivery tip into the beaker, check to see if both the orange and 

green filters are in front of the photocell, and close the cover. (If a spectrophotometer is used, set to 590 m M-)

8. Adjust the light to maximum intensity and then reduce it slightly so that the 

last movement of the pen of the recorder is from right to left.

9. Throw the toggle switch permitting the electromagnetic hosecock to open 

and the recorder to start.
40 CONTRIBUTIONS TO GEOCHEMISTRY

10. As the titration proceeds the pen which is tracing out the curve moves to 

the left as the color changes. (See fig. 11.) When sufficient Versene solution has 

flowed into the beaker to react completely with the calcium the pen will no longer 

move to the left but will trace a line parallel with the chart movement. Allow 

the chart to move about 1 inch past this point, turn all switches to "off" and 

remove the beaker.

11. Transfer 10 ml of the standard CaO solution to a 400-ml titration beaker 

and repeat steps 2 through 10.

12. Transfer 10 ml of solution B to a 400-ml beaker and repeat steps 2 through 

10.

13. The curves are used to obtain the end point of the titrations as illustrated 

in figure 11. A ruled line is extended from the last portion of the curve (the flat 

portion) and another ruled line is extended along the portion of the curve immediately in front of the sudden change of direction. The intersection of the 

ruled lines is the end point. The time, in seconds, required for the titration is 

measured from starting line to the end point. If the chart has lines every % in., 

then the distance between lines represents 15 seconds. Each titration is expressed 

in seconds.

15 

second

End-point

$

\

I- ^

* s

01 

o

V v 

v

S (

s,

f-

§

 

s "s 

S,

 ^ 

. 

^. 

Start

FIOTIRE 11. Titration curve.
RAPID ANALYSIS OF SILICATE ROCKS 41

CALCULATIONS

1. Obtain the blank correction:

r/o f 1 i j.j \ /sees, for 10-mlstd.\~I . ., ,, , ,. [(Sees, for 1-mlstd.) f ^ ) X 1.1= blank correction.

This is a better method of obtaining the blank correction than one in 

which the correction is obtained by direct titration of a reagent blank solution 

because the curve for a reagent blank solution, which usually contains very 

little calcium, will be more poorly defined than one for a solution containing an 

appreciable amount of calcium.

2. Compute the factor:

__________ 3-05 X 100 __________ -factor. 

(Sees, for 10-ml std. blank correction) X 20

3. Calculate percent CaO:

(Factor) X (sees, for sample blank correction) =percent CaO.

MgO

Magnesia (MgO) is determined by titration with, disodium ethylenediamine tetraacetate (Versene) using Eriochrome Black T as an indicator (Betz and Noll, 1950) after the rapid separation of the R203 

group and precipitation of calcium as the tungstate.

REAGENTS

NH*OH, 1+1.

Versene solution: The same solution as used for Determination of CaO.

Buffer solution: Dissolve 66 g of NH*C1 in 1 liter of 1 + 1 NE^OH and store in

plastic bottle.

Sodium tungstate solution, 20 percent: prepare 500 ml. 

Eriochrome Black T indicator solution, approximately 0.2 percent: Prepare 50

ml. This solution should not be kept more than three days. 

CaCl2 solution: Dissolve 500 mg of CaCOs in a few milliliters of HC1 and dilute

to 500 ml with water. 

NH*C1 methyl red solution: Add 10 ml of 0.05 percent methyl red solution to

1 liter of 15 percent NEUCl. 

Standard MgO solution: Transfer 0.752 g of magnesium ribbon or wire to a 250-

ml beaker. Add 10 ml of 1+3 HC1, cover, and boil gently 1 to 2 minutes.

Cool to room temperature and dilute to 200 ml in a volumetric flask. Transfer 50 ml to a 1-liter volumetric flask, dilute to volume, and mix. The solution contains the equivalent of 0.250 mg MgO per ml. Store solution in a

plastic bottle.

PROCEDURE

1. Transfer 25 ml of solution B (equivalent to 50 mg of original sample) to a 

250-ml volumetric flask.

2. Add about 200 ml of water, 15 ml of the NIBUCl-methyl red solution and 

then add 1+1 NIUOH dropwise, until the indicator turns yellow.

3. Dilute to volume, mix, and let stand 15 minutes.

4. Pour through a dry filter paper, or a dry funnel, catching 200 ml of the 

filtrate in a dry 200-ml volumetric flask. The 200 ml of filtrate contains the 

equivalent of 40 mg of original sample.

5. Transfer the contents of the flask to a 400-ml beaker and rinse the flask with 

distilled water.

6. To two additional 400-ml beakers add 1 ml and 10 ml of the standard MgO 

solution. Then add 200 ml of water to each.
42 CONTRIBUTIONS TO GEOCHEMISTRY

7. To each beaker add 5 ml of the CaCl2 solution, 10 ml of the buffer solution, 

and 10 ml of the sodium tungstate solution.

8. Bring the solutions to a boil and allow to boil 2 minutes. Then cool them to 

room temperature in a water bath.

,9. Decant the solutions into 400-ml titration beakers without rinsing. .The 

major portion of the precipitated calcium tungstate will adhere to the sides of the 

beaker. The amount of solution left on the walls is inconsequential and extensiye 

transfer of the tungstate precipitate is undesirable because the resulting clou'dy 

solution diminishes the quality of the titration. Transfer of small quantities of 

precipitate is of no consequence.

10. Add 5 ml of the buffer solution, 1 ml of the Eiiochrome Black T indicator 

solution and fill the beakers to the mark with distilled water.

11. Put a magnetic stirrer in the beaker containing the solution prepared from 

the 1-ml standard, place it in the titrator, and check to see that only the orange 

filter is in front of the photocell. (If a spectrophotometer is used, set at 670 m /».)

12. Adjust the light to maximum intensity and then reduce it slightly so that 

the last movement of the recorder pen is from right to left.

13. Throw the toggle switch permitting the electromagnetic hosecock to open 

and" the recorder to start.

14. As the titration proceeds, the pen which is tracing out the curve moves to the 

left as the color changes (fig. 11). When sufficient Versene solution has flowed 

into the beaker to react completely with the magnesium, the pen will no longer 

move to the left but will trace a line parallel with the direction of the chart movement. Allow the chart to move about 1 inch past this point, turn all switches to 

"off" and remove the beaker. «

15. The curve is used to obtain the end point of the titration as illustrated in 

figure 11. A ruled line is extended from the last portion of the curve (the flat 

portion) and another line is extended along the portion of the curve immediately 

in front of the sudden change of direction. The intersection of the ruled lines is 

the end point. The time, in seconds, required for the titration is measured from 

the starting line to the end point.

16. Repeat steps 11 through 15 for the solution prepared from the 10-ml aliquot 

of the standard solution (step 10).

17. Repeat steps 11 through 15 for the solution prepared from the sample 

solution (step 10).

CALCULATIONS

1. Obtain the blank correction:

ryc, , , i xj N /sees, for 10-ml std.\~L,, ,1.11 __ * I (Sees, for 1-ml std.) ( r^ ) Xl.l=blank correction.

Note: This is a better method of obtaining the blank correction than one in 

which the correction is obtained by direct titration of a reagent blank solution 

because the curve for a reagent blank solution, which usually contains very little 

magnesium, will be more poorly defined than one for a solution containing an 

appreciable amount of magnesium.

2. Compute the factor:

2.5X100 or_

(Sees, for 10-ml std. blank correction)X40

3. Calculate percent MgO:

(Factor) X (sees, for sample blank correction)=percent MgO.
RAPID ANALYSIS OF SILICATE ROCKS 43

K2O AND Na2O

Potassium oxide and sodium oxide are determined by a flame 

photometer method in which lithium is used as an internal standard 

(Brannock and Berthold, 1953). The use of an internal standard 

reduces the effects due to differences in concentration of dissolved 

salts and differences in viscosity between standard and sample solutions and also reduces deviations in readings brought about by changes 

in the character of the flame resulting from small variations in air 

and gas pressures.

Satisfactory results for the alkalies are obtained by comparing 

each sample solution with two standard solutions one in which the 

concentration of the alkali being determined is higher than in the 

sample solution, and the other in which it is lower. The concentration 

interval of the standard solutions used is relatively small and as a 

result the relationship between concentration of KaO or Na-sO in the 

standard and sample solutions is essentially linear.

REAQENTS

KC1, NaCl, Li2S04 .H2O, all A. C. S. grade.

Stock solution of KCl: Prepare 2 liters of solution in which the concentration of 

K2O is 0.5 mg per ml, using 1.584 g of dry KCl and distilled water. Store 

in a Pyrex or plastic bottle.

Stock solution of NaCl: Prepare 2 liters of solution in which the concentration of 

Na^O is 0.5 mg per ml, using 1.886 g of dry NaCl and distilled water. Store 

in a plastic bottle.

Stock solution of Li2SO4 : Prepare 10 liters of solution in which the concentration 

of lithium is 2,000 ppm, using 184.4 g of Li2S04 .H2O and distilled water. 

Store the solution in a Pyrex bottle.

Standard K20 solutions: Prepare solutions so that the concentration of K2 0 

and lithium will be the same as that in sample solutions prepared, as described 

below in step 3 of Procedure, for samples containing exactly 0.5, 1, 2, 4, 6, 8, 

and 10 percent K2 0, by diluting 5, 10, 20, 40, 60, and 100 ml of the stock 

solution of KCl and 50 ml of the stock solution of Li2S04 to 1 liter with distilled water.

Standard Na2O solutions: Prepare solutions so that the concentration of Na^O 

and lithium will be the same as that in sample solutions prepared, as described 

below in step 3 of Procedure, for samples containing exactly 0.5, 1, 2, 4, 6, 

8, and 10 percent K2 0, by diluting 5, 10, 20, 40, 60, and 100 ml of the stock 

solution of NaCl and 50 ml of the stock solution of Li2SO4 to 1 liter with water.

Internal standard solution: Prepare 2 liters of solution in which the concentration 

of lithium is 200 ppm, by diluting 200 ml of the stock solution of Li2S04 with 

distilled water.

PROCEDURE

1. Light the burner of the flame photometer and adjust the flame as described 

under Apparatus and instruments Flame photometer.

2. Turn the electric switch on the panel of the flame photometer to the "on" 

position.

3. To 25 ml of solution B in a Pyrex beaker or bottle add 25 ml of distilled 

water and 50 ml of the internal standard solution, containing 200 ppm lithium, 

and mix. (Reservoir-type automatic pipets can be used to advantage in the 

addition of the water and the internal standard solutions.)
44 CONTRIBUTIONS TO GEOCHEMISTRY

4. If the approximate concentration of potassium in the sample solution can 

be estimated, omit steps 4 through 7 and proceed with step 8. If the approximate 

concentration of potassium in the sample solution cannot be estimated, pour 25 

to 30 ml of the standard K2O solution, in which the concentration of K2 O is 

equivalent to that of a solution prepared from a sample containing 10 percent 

K2O, into a 50-ml beaker. Place the beaker containing the standard solution in 

position on the beaker stand so that the atomizer inlet tube is immersed in the 

solution. As the solution atomizes into the flame, set the element selector to the 

position of maximum response for potassium.

5. With the same solution (step 4) atomizing into the flame set the internal 

standard dial to approximately 95 and adjust the coarse and fine gain controls 

so that the meter reads 50. Remove the beaker containing the standard solution 

and with no solution atomizing set the meter to read 50 with the zero adjusting 

knob. Replace the beaker with the same standard solution and while the 

solution atomizes adjust the internal standard dial so that the meter reads 

exactly 50. Record the setting of the internal standard dial. Remove the 

beaker and wipe the outside of the liquid inlet tube of the atomizer with a clean 

lintless tissue.

6. Put 25 to 30 ml of the sample solution (step 3) into a 50-ml beaker and place 

in position so that it atomizes into the flame. Adjust the internal standard dial 

so that the meter reads exactly 50. Remove the beaker, wipe the atomizer tube 

with a tissue, and record the setting of the internal standard dial.

7. Assume the recorded reading to be proportional to the concentrations of 

potassium in standard and sample solutions, and calculate the approximate 

concentration of potassium as K2O.

8. Repeat step 5 using the standard solution with the nearest higher concentration to the estimated concentration of potassium in the sample solution.

9. Repeat step 6.

10. Repeat step 6 using the standard solution with the nearest lower potassium 

concentration to the estimated concentration of potassium in the sample solution.

11. With the same solution (step 10) atomizing, shift the position of the 

internal standard dial and then reset it so that the meter again reads 50. Record 

the setting of the internal standard dial, remove the beaker and solution and wipe 

the atomizer tube.

12. Repeat step 6.

13. Repeat step 6 using the higher standard instead of the sample solution.

14. Na-jO is determined on a portion of the same sample solution which waa 

used for the determination of K2O (step 4). The element selector is set to the 

position of maximum response for sodium and the Na^O is determined in the 

same way as K2O.

CALCULATIONS

1. The two-point equation below is used to calculate the concentration of K2O 

and Na2O in the sample solution after averaging the readings obtained for each 

standard and the sample solution.

_ y 2/1 ,

2/2-2/1

x = concentration of K2O in the sample solution 

y =dial reading for the sample solution 

Xi = concentration of K2 O in the lower standard solution 

yi = dial reading for the lower standard solution 

x2 =concentration of K2O in the higher standard solution 

?/2=dial reading for the higher standard solution
RAPID ANALYSIS OF SILICATE ROCKS 45 

FeO

Ferrous iron is determined by the conventional titrimetric method 

using standard dichromate solution with diphenylamine sulfonic acid 

as the indicator (Sarver, 1927). When decomposition is carried out 

on batches of about eight samples simultaneously the time consumption per sample is small.

REAGENTS

H2S04 , 48 percent HF, K2Cr2 07 , all A. C. S. grade.

H2S04 , 1 + 3.

Diphenylamine sulfonate indicator: Dissolve 0.2 g of sodium diphenylamine 

sulfonate in 1 liter of water. Add 1 liter of 85 percent H3P04 and mix well.

Standard dichromate solution: Weigh 2.728 g of dry National Bureau of Standards potassium dichromate or other pure dry potassium dichromate and 

dilute to 2 liters in a volumetric flask. The solution contains the equivalent 

of 2.000 mg FeO per ml.

PROCEDURE

1. Weigh 0.500 g of sample and place in platinum crucible of approximately 

100-ml volume.

2. Add 20 ml of 1 + 3 H2S04 to the crucible, cover, and carefully bring to a boil 

over a gas burner or an electric heater.

3. Add about 10 ml of HF. Cover and again bring to a boil. Boil gently for 

15 minutes.

4. While the solution in the crucible is boiling, add 400 ml of water and approximately 10 g of boric acid to an 800-nil beaker. Stir the liquid in the beaker to 

aid in solution of the boric acid.

5. After the solution in the crucible has boiled for 15 minutes, remove the 

crucible from the heat with tongs, hold the cover on the crucible with a stirring 

rod, and immediately immerse the covered crucible and contents in the boric acid 

solution. The crucible should be kept covered after immersion, until just before 

the titration.

6. Add 10 ml of the indicator solution and titrate the solution with standard 

dichromate solution to a purple end point which persists for 20 to 30 seconds.

CALCULATIONS

1. Compute percent FeO in the sample:

Dichromate (ml) X2.000 ^ ._. , ,, n 

 ~: - X 100=percent FeO. 

ouu

Dichromate (ml) X 0.4 = percent FeO. 

H2O

Water is determined by a modification of the Penfield method 

(Shapiro and Brannock, 1955b). The modified procedure is simpler 

and less time consuming than the conventional method.

REAGENTS

Sodium tungstate, anhydrous powder: Fuse several hundred grams of reagent 

Na2WO4 - 2H2 0. Allow to cool, grind to a fine powder, and store in a jar with 

a tight-sealing cap.
46 CONTRIBUTIONS TO GEOCHEMISTRY

PROCEDURE

1. Transfer 1.000 g of sample powder to a dry 18 mm by 150 mm Pyrex test 

tube by means of a funnel. (For samples containing appreciable amounts of 

sulfur, mix 3 g of anhydrous sodium tungstate with the sample powder before 

placing into the tube.)

2. Cover the fingers of the hand which is easier to use in manipulation with 

finger stalls or a rubber glove. Roll a piece of 2 in. by 2 in. filter paper into a 

cylinder, slip it into an 18 mm by 65 mm tube, stopper the tube with a solid 

stopper and weigh. (To avoid absorption of moisture from the fingers, the paper 

should be handled only with covered fingers.)

3. Quickly transfer the paper cylinder from the weighing tube to the upper 

part of the 18 mm by 150 mm test tube which contains the sample powder and 

stopper with a one-holed stopper.

4. Place a 2 in. by 3 in. piece of wet paper around the outside of the upper 

portion of the ignition tube to cool the tube.

5. Place the tube in a horizontal position in a holder at a height that will allow 

the tube to get maximum heat from a Fisher burner (fig. 9).

6. Heat the closed end of the tube, gently at first, then at full heat of the burner 

for 5 minutes. Finally play the flame along the tube below the filter paper for 1 

to 2 seconds to drive the water into the upper part of the tube. Allow to cool for 

at least 1 minute.

7. Remove the stopper and with the aid of a narrow spatula quickly wipe the 

walls of the tube surrounding the paper by gently pressing and rotating the filter 

paper cylinder one full rotation. With the fingers covered, quickly transfer the 

paper from the test tube to the weighing tube and replace the stopper in the 

weighing tube.

8. Weigh the tube containing the filter paper plus the absorbed water.

CALCtHLATIONS

1. Subtract the weight obtained in step 2 from the weight obtained in step 8 to 

obtain the weight of absorbed water.

2. A small part of the expelled water is not condensed and caught by the filter 

paper strip. A simple rule, which has been derived empirically, is used to get the 

value for total water in the sample from the value for water absorbed. If the 

amount of absorbed water is 20 mg or less, increase the value by 10 percent. If 

the amount of absorbed water is over 20 mg, add 2 mg to the value obtained.

3. Calculate percent water:

(Absorbed water, mg + correction, mg) ± -a r\ - ' ^ '- =percent H2O.

CO2

Carbon dioxide is determined by measuring the volume of gas 

evolved when powdered sample is heated with acid in a simple tube 

designed for the purpose (Shapiro and Brannock, 1955a). The carbonate tube is described under Apparatus and instruments and is 

shown in figure 10. In the method described below for Calibration 

of the carbonate tube, National Bureau of Standards standard 

sample 79 (fluorspar), which contains 0.97 percent CO2 , is used. Any 

other material containing about 1 percent CO2 for which an accurate 

value is known can be used if the standard sample is not available.
RAPID ANALYSIS OF SILICATE ROCKS 47

Wet paper for cooling 

Paper absorber

FmuEE 12. Water tube being heated on a support. 

REAGENTS

HC1, 1+1.

HgCl2, 3 percent: Prepare 100 ml. This solution is used to prevent the evolution

of hydrogen which would otherwise occur as the result of the reaction between

hydrochloric acid and "tramp iron" which may have been introduced as a

contaminant by the sample-grinding apparatus. 

Motor oil, S. A. E. no. 10. Addition of a small amount of antifoaming agent is

desirable, although not essential.

CALIBRATION OP THE CARBONATE TUBE

1. Weigh 1.03 g of National Bureau of Standards standard sample no. 79 and 

transfer it by means of a dry funnel to the bottom of the carbonate tube.

2. Add 2 ml of the HgCl2 solution and tap the tube to free entrapped air 

bubbles.

3. Add oil to the oil level mark.

4. Tilt the tube to allow all the air to escape from the side arm. Then return 

the tube to a position such that the main part of the tube is vertical.
48 CONTRIBUTIONS TO GEOCHEMISTRY

5. Add 2 ml of 1 + 1 HC1 and tilt the tube so that the side arm is vertical to 

allow any COa produced to enter the side arm.

6. Heat the aqueous phase in one of two ways, either with a small gas flame 

or by means of an electrical heater so that it boils gently for 2 to 2}^ minutes.

7. Allow cool tap water to flow down the outside of the side arm for 5 seconds. 

Remove from the stream of tap water and after 30 seconds mark the position of 

the meniscus on the side arm. This is the 1 percent mark.

8. Repeat steps 1 through 7 using 0, 0.206, 0.412, 1.54, 1.85 and 2.06 g of the 

standard sample to obtain the calibration marks for 0, 0.2, 0.4, 1.5, 1.8, and 2.0 

percent CO2, respectively.

9. The tube can now be marked off by interpolation to give marks for each 0.1 

percent CO2 .

PROCEDURE

1. Transfer 1.000 g of sample powder to the bottom of the carbonate tube by 

means of a dry funnel.

2. Proceed as described in steps 2 to 6 under Calibration _of the carbonate tube.

3. Allow cool tap water to flow down the outside of the side arm for 5 seconds. 

Remove from the stream of tap water and after 30 seconds estimate the percent 

CO2 from the scale on the side arm.

EXPERIMENTAL RESULTS

The methods described have been tested by analyzing 12 synthetic 

samples, 2 clay samples, a granite sample, and a diabase sample.

The synthetic samples were prepared by mixing National Bureau of 

Standards standard samples of limestone, dolomite, iron ore, bauxite, 

flint clay, plastic clay, feldspar, silica brick, and phosphate rock. 

These mixtures were prepared to include constituents which might be 

expected to be found in typical silicate rocks in appropriate concentration ranges. In several of the samples the concentration of CC>2 was 

much higher than is found in typical silicate rocks. The concentration ranges are shown in table 2.

Table 3 shows the results obtained by two rapid analyses, made at 

widely different times, of the National Bureau of Standards mixture 

samples, compared with values computed from the analyses reported 

for the original samples by the Bureau of Standards.

The carbon dioxide concentrations in typical silicate rocks usually 

do not exceed several percent. The precision of the rapid procedure 

for CO2 , which was designed for typical silicate rocks, falls off appreciably for samples containing abnormally high concentrations of this 

constituent. Better results can be obtained for samples in which 

CO2 exceeds 10 percent by calculations based on ignition loss determinations.

Table 4 shows the results obtained by two rapid analyses also made 

at widely different times of two clay samples, National Bureau of 

Standards standard samples 97 (flint clay) and 98 (plastic clay).

The National Bureau of Standards certificates do not supply information on some of the constituents for which data are shown for
RAPID ANALYSIS OF SILICATE ROCKS 49

rapid analyses. In these cases the results for the rapid analyses are 

shown to indicate precision only.

A comparison of results obtained by rapid and conventional analysis 

for two rock samples that were used in an extensive collaborative study 

of precision and accuracy of silicate rock analysis (Fairbairn and others, 

1951) is shown in table 5.

The averages of the values for double runs shown in tables 3, 4, and 

5 are comparable to results obtainable by conventional means as 

demonstrated in Geological Survey Bulletin 980 (Fairbairn and others, 

1951). The indicated accuracy for single runs would be satisfactory 

for many purposes where great saving in time and cost is important.

REFERENCES CITED

Bandemer, Selma L., and Schaible, P. J., 1944, Determination of iron: Indus.

and Eng. Chemistry, Anal. Ed., v. 16, p. 317-319. 

Barredo, J. M. G., and Taylor, J. K., 1947, Automatic recording of titrations:

Electrochem. Soc. Trans., v. 92, p. 437-440. 

Betz, J. B., and Noll, C. A., 1950, Total-hardness determination by direct colorimetric titration: Am. Water Works Assoc. Jour., v. 42, p. 49-56. 

Brannock, W. W., and Berthold, Sarah M., 1953, The determination of sodium

and potassium in silicate rocks by flame photometer: U. S. Geol. Survey

Bull. 992, pt. 1, p. 1-14.

Bunting, W. E., 1944, The determination of soluble silica in very low concentration: Indus, and Eng. Chemistry, Anal. Ed., v. 16, p. 612-615. 

Fairbairn, H. W., and others, 1951, A cooperative investigation of precision and

accuracy in chemical, spectrochemical and modal analysis of silicate rocks:

U. S. Geol. Survey Bull. 980. 

Hillebrand, W. F., 1900, Some principles and methods of rock analysis: U. S.

Geol. Survey Bull. 176.

Kitson, R. E., and Mellon, M. G., 1944, Colorimetric determinations of phosphorus as molybdivanadophosphoric acid: Indus, and Eng. Chemistry, Anal.

Ed., v. 16, p. 379-383. 

Parker, C. A., and Goddard, A. P., 1950, The reaction of aluminum ions with

alizarin-3-sulphonate, with particular reference to the effect of calcium ions:

Anal. Chem. Acta., v. 4, p. 517-524. 

Sarver, L. A., 1927, The determination of ferrous iron in silicates: Am. Chem.

Soc. Jour., v. 49, p. 1472-1477. 

Shapiro, Leonard, and Brannock, W. W., 1952, Rapid analysis of silicate rocks:

U. S. Geol. Survey Circ. 165.

 1955a, Rapid determination of CO2 in silicate rocks: Anal. Chemistry, v. 

27, p. 1796 97.

1955b, Rapid determination of water in silicate rocks: Anal. Chemistry,

v. 27, p. 560-564. 

Willard, H. H., and Greathouse, L. H., 1917, The colorimetric determination of

manganese by oxidation with periodate: Am. Chem. Soc. Jour., v. 39, p.

2366-2377. 

Yoe, J. H., and Armstrong, A. R., 1947, Colorimetric determination of titanium

with disodium-1, 2-dihydroxbenzene-3, 5-disulfonate: Anal. Chemistry, v.

19, p. 100-102.
50 CONTRIBUTIONS TO GEOCHEMISTRY

TABLE 1. Conversion of percent transmission (T) to absorbance (A).

T

30. 0

30. 5

31.0

31. 5

32.0

32.5

33. 0

33. 5

34. 0

34. 5

35. 0

35. 5

36.0

36.5

37.0

37.5

38. 0

38.5

39.0

39.5

40.0

40. 5

41. 0

41. 5

42.0

42. 5

43. 0

43. 5

44. 0

44. 5

45.0

45. 5

46.0

46. 5

47. 0

47. 5

48.0

48. 5

49. 0

49. 5

A

0. 523

. 516

. 509

. 502

.495

.488

.482

. 475

. 469

. 462

.456

. 450

. 444

.438

.432

.426

.420

. 415

. 409

. 403

. 398

. 393

.387

. 382

. 377

.372

. 367

. 362

. 357

. 352

. 347

. 342

.337

.333

.328

. 323

. 319

.314

. 310

. 305

T

50. 0

50. 5

51.0

51. 5

52.0

52. 5

53.0

53.5

54.0

54. 5

55.0

55. 5

56.0

56. 5

57. 0

57. 5

58.0

58.5

59.0

59. 5

60. 0

60. 5

61. 0

61. 5

62. 0

62. 5

63.0

63. 5

64. 0

64. 5

65. 0

65.5

66. 0

66. 5

67. 0

67. 5

68. 0

68. 5

69. 0

69. 5

A

0. 301

.297

.292

. 288

. 284

. 280

. 276

.272

. 268

. 264

.260

. 256

. 252

. 248

. 244

. 240

. .237

. 233

. 229

. 226

.222

.218

. 215

.211

. 208

. 204

. 201

. 197

. 194

. 190

. 187

. 184

. 180

. 177

. 174

. 171

. 168

. 164

. 161

. 158

T

70. 0

70. 5

71.0

71. 5

72.0

72. 5

73.0

73. 5

74. 0

74.5

75. 0

75. 5

76. 0

76. 5

77. 0

77. 5

78. 0

78. 5

79.0

79.5

80. 0

80. 5

81. 0

81. 5

82. 0

82. 5

83.0

83.5

84.0

84. 5

85. 0

85. 5

86. 0

86. 5

87. 0

87. 5

88.0

88. 5

89.0

89.5

A

0. 155

. 152

. 149

. 146

. 143

. 140

. 137

. 134

. 131

. 128

. 125

. 122

. 119

. 116

. 114

. Ill

. 108

. 105

. 102

. 100

.097

. 094

.092

.089

.086

. 084

.081

.078

.076

. 073

. 071

.068

.066

.063

.060

. 058

.056

.053

. 051

.049

T

90. 0

90.5

91.0

91. 5

92.0

92. 5

93. 0

93. 5

94.0

94. 5

95.0

95.5

96.0

96. 5

97.0

97.5

98.0

98.5

99.0

99. 5

A

0.046

.043

.041

.039

.036

.034

.032

.029

.027

.025

.022

.020

.018

. 016

.013

.011

.009

.007

.004

.002
RAPID ANALYSIS OF SILICATE ROCKS 51

TABLE 2. Concentration ranges of the test samples.

Constituent _ Range

SiOj__________________________________________«________ 24 -80

AljO,.__..._____________________________________________ 9 -36

Total Fe, as FejO......____________________:__ 0. 8 -16

FeO.._________ _-__________________________________ .06-8.7

TiOj____.______________________________________________ . 01- 2. 5

MnO______________________________________________ . 00- 0. 28

P2O6 _____________________________________________ .04-2.4

CaO_____________._____________________________________ . 10-15

MgO________________________________________________ .04-8.1

Na_O__________________________________________________ .09-7.0

KjO_________________________________________________L_ .19- 8.3

COj__._________________________________________________ . 00-17. 6

HjO_._________________________________________________ .34-14 2

TABLE 3. Results obtained for National Bureau of Standards (NBS) mixture

samples (A to L)

[Asterisk indicates determination based on ignition loss]

Si02 ________________

A12O3 ---------------

FeO________________

Fe2O3 __ ._.__-_....

TiO2 __-_--_______.__

MnO___.___________

P206 ________________

CaO____-___________

MgO_-._. __________

Na_O_---_--____-__.

K2O_-_-_-_-___-__-_

H2O________-_____._

CO2 ________________

Total Fe as 

Fe2 03 ----_-

1

24.6

24.8

.05

1.9

.87

.00

.26

10.4

6.9

. 76

4. 1

9.5

2.0

1

Rapid

2

24. 7

24.0

.07

1.8

. 90

.00

.25

10.4

7.0

.77

4. 1

9. 7

1.9

i

Av.

24. 6

24.4

.06

1.8

.88

.00

.26

10.4

7.0

. 76

4. 1

9.6

*16. 1

100.0

2.0

"vruQ

24.2

24.2

. 92

.27

10.5

7. 1

.81

4.2

2.0

1

37. 1

37. 1

.06

2.8

1.3

.00

.80

1.2

.02

5.4

. 19

14.3

. 16

2.9

I

Rapid

2

36.9

36.3

2.8

2.8

1.3

.01

.77

1.2

.06

5.4

.21

14.2

.18

2.9

5

Av.

37.0

36. 7

2.8

2.8

1.3

.00

.78

1.2

.04

5.4

.20

14.2

. 17

99.8

2.9

"vruc!

36.8

36.3

1.4

.80

1.3

.04

5.3

.20

2.9
CONTRIBUTIONS TO GEOCHEMISTRY

TABLE 3. Results obtained for National Bureau of Standards (NBS) mixture 

samples (A to L) Continued

SiO2 __-----_--______

A12O3 ---------------

FeO-----_- -.._....

Fe2O3 ----_ -._-_-_

TiO2 .__ .-_-..._..___

MnO__-__. __-...__.

P2 06 .-_--.-._.__

CaO ---_-__-_____

MgO -._._.-......_

Na2O_----__-_______

K2O.___ _..__._.____

H2O..___ __....__

C02 _-______-_______

Total Fe as 

Fe2O3 _______

SiO2 -__ 

A12O,_ ___________

FeO___ __________

Fe2O3 --_-_-_-______

Ti02 -------------

MnO---_----_-_____

P2 05 _____________

CaO____. .____-____.

MgO-___-___.-_____

Na2O__-_____-______

K2 0_.-_. -._______..

H2 0.-__--________-_

C02 _--_. ___________

Sum __ _____ ___

Total Fe as 

Fe2O3 --_-__

1

35. 7

26.0

. 16

Q 8

.78

.01

.41

3.9

2.3

1.2

6. 1

8.7

4 Q

9.9

1

46. 8

12. 7

.25

15. 4

.00

.01

2. 4

6. 7

2.6

7.0

. 28

. 74

4. 4

15. 6

(

Rapid

2

36.0

25.2

. 14

Q 8

.84

.01

.40

3.8

2.4

1. 1

6. 1

8. 6

5. 1

9.9

I

Rapid

2

46. 5

13. 1

.23

15. 9

.02

. 03

2. 3

6. 9

2.8

6.9

. 28

. 78

4. 6

16. 1

1

Av.

35.8

25.6

. 15

9.8

.81

.01

.40

3.8

2.4

1.2

6. 1

8. 6

5.0

QQ 7

9. 9

:

Av.

46. 6

12. 9

. 24

15.6

.01

.02

2. 4

6. 8

2. 7

7. 0

. 28

.76

4. 5

QQ 8

15. 8

NBS

35.4

25.4

.84

.39

3.9

2.5

1.2

6.2

10. 1

xmc!

46. 4

12. 7

.03

2. 4

6.8

2. 7

7. 0

.28

15. 8

1

71.3

9.3

. 14

11. 6

.02

.01

.29

. 70

.46

5. 1

.20

.46

.53

11.7

1

45.2

12. 1

.22

7. 7

.00

.00

2.0

8. 8

4. 3

1. 5

8.2

. 51

8. 6

7. 9

I

Rapid

2

70.5

9. 6

. 14

11. 7

.05

.01

.28

.84

.50

5.2

.20

.43

.55

11.8

I

Rapid

2

45. 4

12. 3

. 18

7.6

.00

.01

1. 9

8.8

4. 5

1. 5

8. 1

. 48

8.6

7.8

)

Av.

70.9

9.4

. 14

11.6

.04

.01

.28

.77

.48

5.2

.20

.44

.54

100.0

11.8

" 

Av.

45.3

12. 2

.20

7.6

.00

.00

2.0

8.8

4.4

1. 5

8. 2

. 50

8.6

99.3

7.8

NBS

71.0

9.3

.06

.25

.78

.50

5. 1

. 19

12.0

M"RC!

45.0

12. 1

.01

2.0

8. 8

4. 4

1. 6

8.3

8.0
RAPID ANALYSIS OF SILICATE ROCKS 53

TABLE 3. Results obtained for National Bureau of Standards (NBS) mixture 

samples (A to L) Continued

SiOj ..._._. ______

A12O3 - __ ___________

FeO__-._. ..__._____

Fe2O3______. ________

 no, _____________

MnO_--.____.____ _

P_0,_ ____________

CaO________________

MeO

Na2O_______________

K2O-___-___._______

H2O_. __________

CO.---_-___________

Sum __ __ _ _______

Total Fe as 

Fe2O3 _ ______

SiO2 ________________

Al2O3 ----__--_._____

FeO

Fe2O3 .______________

TiO2 -___-.__________

MnCL________ _ _

P205 _____________

CaO-_.____________

MgO_______________

Xa2O---------------

K2O---_____--____-

H2O___.____________

CO2 ---___.___-_____

Total Fe as 

Fe2O3 _.-____

1

37.3

10. 1

.08

^ Q

.00

.02

1.0

12. 6

8.0

1.3

7.0

.40

4 0

1

79, 1

12. 8

00

. 82

. 74

.00

.07

. 16

.36

.20

1. 6

4.0

.00

1.2

(

Rapid

2

37.6

10. 2

. 11

^ Q

.01

no

1.0

13. 1

8. 2

1. 3

6. 9

. 49

4.0

]

Rapid

2

78. 5

12. 6

.35

.62

.74

.00

.05

. 12

. 43

. 22

1. 6

3. 9

.00

1.0

1

Av.

37. 4

10.2

. 10

3. 9

.00

.01

1. 0

12. 8

8. 1

1.3

7.0

. 44

*17. 6

99. 8

4.0

[

Av.

78. 8

12. 7

.36

.72

.74

.00

.06

. 14

. 40

. 21

1.6

4 0

.00

99. 7

1. 1

TVTUCS

37.6

10. 1

.01

1.0

12.8

8. 1

1. 4

7.0

4.0

AT "DO

79. 1

12. 9

.76

.04

. 12

.37

. 14

1.6

1. 1

1

45.0

12. 9

. 32

6.0

.04

.03

1. 5

14. 5

. 94

6. 5

.47

.82

9.2

6.3

1

75. 9

13. 7

. 44

1.0

.78

.00

.07

1.3

. 42

. 17

1. 6

4. 1

.00

1. 4

I

Rapid

2

45. 5

12.7

. 36

6. 1

.07

.03

1.5

14 7

.86

6.7

.44

.88

9.8

6. 4

Rapid

2

76.7

13.6

. 40

1.0

.80

.01

.09

1. 3

. 51

. 17

1. 6

4. 1

.00

1. 4

I

Av.

45. 2

12. 8

.34

6.0

.06

.03

1. 5

14. 6

. 90

6. 6

.46

.85

9.5

98. 9

6.4

]

Av.

76. 3

13. 6

. 42

1. 0

.79

. 00

. 08

1. 3

.46

. 17

1. 6

4 1

.00

99. 7

1. 4

ATTIC!

45. 6

12. 7

.06

1. 5

14. 6

, . 91

6. 5

. 46

6.4

ATUQ

76.5

13. 8

. 80

. 05

1. 2

.46

. 17

1. 7

1. 4
54 CONTRIBUTIONS TO GEOCHEMISTRY

TABLE 3. Results obtained for National Bureau of Standards (NBS) mixture 

samples (A to L) Continued

SiO2~--------- - _--

A12O3 - --- _ ____

FeO... .--_... ....._

Fe_O3-----_--------

TiO2 ..-__._. ________

MnO______.-___-___

P20.__________._____

CaO_-_____________

MgO. _ __

Na2O___. ___________

K_0__----___--____

H.O_-__--_. ________

C02 _-_--_ -_-.-_

Sum_______ _________

Total Fe as 

Fe2 0, .___

1

67. 7

19. 4

. 15

.75

1.3

.40

.06

1.2

.20

.03

.42

fi Q

.00

90

I

Rapid

2

68.0

1Q 4

. 13

. 60

1.3

. 44

.07

1. 1

.27

.06

.41

fi Q

.00

.73

C

Av.

67.8

1Q 4

. 14

.66

1.3

.42

.06

1. 2

. 24

.04

. 42

6 9

.00

98. 6

. 81

NBS

68. 1

20.3

1.3

.42

.05

1.2

.23

.09

.41

.82

1

63.4

21. 7

. 11

1.0

. 70

.26

. 13

.32

.36

5.3

1.7

4.2

.00

1. 1

]

Rapid

2

64.2

21. 7

. 13

1.0

.73

.26

. 13

.30

.28

5.5

1.8

4. 1

.00

1. 1

L

Av.

63. 8

21. 7

. 12

1.0

.72

.26

. 13

. 31

.32

5.4

1.8

4.2

.00

99.8

1. 1

NBS

63.7

22.2

.72

.28

. 11

.28

.38

5.5

1.8

1. 1
RAPID ANALYSIS OF SILICATE ROCKS 55

TABLE 4. Results obtained for two National Bureau of Standards standard clay

samples (97 and 98)

-

SiO__ _--_ _-_

A1_O__- _--____

FeO _._____

Fe2O3 -- ____ -----

TiO2 ------------

MnO ._

P206 -- -_ 

CaO ____ ,_ ._- _

MeO

NaaO------.--.-...-

K_O_ -____- -__

H_O _-___ -_ 

CO__ _ _-___

Sum _ _________ _ _

Total Fe as 

Fe2O3 --_-

1

43.0

38.4

.52

.43

2.4

.00

. 12

. 16

.22

. 18

.53

13.3

.00

.95

9

Rapid

2

43.0

38.2

.51

.40

2.4

.00

. 10

. 12

.26

. 10

.54

13.0

.00

.91

7

A.V.

43.0

38.3

.52

.42

2.4

.00

. 11

. 14

.24

. 14

.54

13.2

.00

99.0

.93

TVT"DC!

42.9

38.8

2.4

.08

.10

.26

. 12

.54

.98

1

58.6

25.5

.58

1.4

1.4

.00

. 13

.21

.68

.32

3. 1

7.5

.00

2.0

9

Rapid

2

58.5

24.9

.60

1.3

1.4

.00

. 11

.25

.71

.31

3. 1

7. 6

.00

1.9

8

Av.

58.6

25.2

.59

1.4

1.4

.00

. 12

.23

.70

.32

3. 1

7.6

.00

99.2

2.0

TVT"DC!

59. 1

25.5

1.4

.08

. 21

.72

.28

3.2

2.0
56 CONTRIBUTIONS TO GEOCHEMISTRY

TABLE 5. Results obtained by rapid and conventional analysis of two carefully studied

rock samples

IResults shown for conventional method are averages of results obtained by five analysts in another laboratory of the Geological Survey. The samples used are described by Fairbairn and others (1951).]

SiO2 ---- _ -___--..

A12O3 ---. ----------

FeO----_----------

Fe2O3 . __ __._---

TiO2 ...__. ----------

MnO..___- _ ------

P2 0S .... --

CaO-_._ -.-_--.--_--

MgO ___ ___ -__

Na2O_. ..... --------

K2O ._.-. .___-_--

H2O-_-__.._-..--_-

C02 -__. -..._. ..----

Sum __ ____ ____ _

Total Fe as 

Fe2O3 _ - _

1

72.4

14.7

.97

. 84

.23

.02

.08

1.3

.34

3.3

5.4

. 30

. 10

1.8

Granit*

Rapid

2

72.5

14.3

. 94

. 87

.24

.02

.07

1.4

.28

3.3

5.4

. 32

. 12

1.8

a(G-l)

Av.

72.4

14. 5

. 96

. 86

.24

.02

.08

1.4

.31

3.3

5.4

. 31

. 11

99.9

1.8

Contional

72.5

14.3

.95

.84

.25

.03

.09

1.3

.36

3.3

5.5

.34

.07

1

52.7

15.3

8. 8

1.2

1.0

.18

. 17

10. 8

6.5

2.2

. 66

.52

.07

10.8

Diabase

Rapid

2

52. 7

14.9

8.8

1.4

1. 1

.20

. 16

10. 6

6.7

2. 1

.62

.56

.05

11.0

5 (W-l)

Av.

52. 7

15. 1

8.8

1. 3

1.0

. 19

. 16

10. 7

6.6

2.2

.64

. 54

.06

100.0

10.9

Contional

52. 6

15.2

8.7

1.4

1. 1

. 16

. 15

10.9

6.6

2. 1

.66

.59

.05

o