GEOLOGICAL SURVEY CIRCULAR 165

RAPID ANALYSIS OF SILICATE ROCKS

By Leonard Shapiro and W. W. Brannock

UNITED STATES DEPARTMENT OF THE INTERIOR 

Oscar L. Chapman, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

GEOLOGICAL SURVEY CIRCULAR 165

RAPID ANALYSIS OF SILICATE ROCKS

By Leonard Shapiro and W. W. Brannock

Washington, D. C.. 1952

Free on application to U. S. Geological Survey, Washington 25, D. C.

ABSTRACT

Rapid methods are described for the determination of the 

major constituents in silicate rocks. SiOg and AlgC^ are 

determined spectrophotometrically on aliquots of a solution prepared by fusion of the sample with NaOH. A molybdenum blue 

method is used for SiOg and f err on is used in the determination 

of A^OS. A second solution prepared by digestion of the sample 

with HF and HgSC^ is used for the determination of TiOg," total 

iron, MnO and PgO5> by spectrophotometric methods. TiO2 is 

determined as the peroxide, total iron as ferric chloride, MnO 

as permanganate, and FgOg as molybdivanado phosphoric acid. 

Additional aliquots of the solution prepared after digestion with 

HF plus H2SO4 are used for the determination of CaO and MgO 

by titration methods, using versene. Another aliquot of the 

same solution is used for the determination of KgO and NagO by 

flame photometer. FeO is determined by titration with KgCrgOY 

after decomposition of the sample with HF and HgSO^.. Loss on 

ignition is determined so that a summation may be obtained and 

used as an aid in checking the reliability of the results. A 

schedule for rapid complete analysis of silicate rocks in sets of 

eight samples is given. Results of rapid analysis of twelve 

synthetic mixtures prepared from National Bureau of Standards 

standard samples are compared with values based on those reported by the Bureau of Standards.

RAPID ANALYSIS OF SILICATE ROCKS

CONTENTS

Page

Abstract...................... ii

Introduction .................... 2

Special apparatus ................. 3

Spectrophotometer ............. 3

Flame photometer ............. 3

Preparation of sample solutions ......... 5

Discussion ..... ............. 5

Reagents . ........ ......... 5

Solution A ............. ..... 7

Solution B ............... ... 7

Determination of SiO2 ........... ... 7

Determination of Al2Os .............. 8

Determination of total iron as Fe0Oo ....... 9

Page

Determination of TiO£ .............. 9

Determination of p£0§ ............. 10

Determination of MnO .............. 10

Determination of CaO .............. 11

Determination of MgO .............. 11

Determination of K^O and Na£O ......... 12

Determination of FeO .......... .... 13

Determination of loss on ignition ....... . 14

Experimental results ............. . 14

Suggested schedule for rapid analysis of

eight silicate rock samples .......... 16

References cited ........ ........ 17

ILLUSTRATIONS

Page

Figure 1. Flow diagram for rapid analysis of silicate rocks ........................... 2

2. Test tube adaptor for the spectrophotometer ............................. 4

3. Special glass atomizer for the flame photometer ........................... 6

TABLES Page

Table 1. Conversion of percent transmission (T) to absorbance (A) ..................... . 5

2. Percentage composition of National Bureau of Standards standard

samples in the mixture samples .................................. . 14

3. Results obtained for National Bureau of Standards mixture samples ................. 15

4. Concentration ranges covered and deviations for National Bureau of Standards mixture

samples ................................................ 16

INTRODUCTION

It is well known that chemical analysis of silicate 

rocks by classical methods is costly and time consuming. In order to increase the applicability and use 

of chemical analyses of silicate rocks, a program of 

research aimed at reducing the cost and the time required for analysis is being carried out in the 

Washington analytical laboratory of the U. S. Geological 

Survey.

As a first approach to this problem we have 

selected and developed procedures for the major constituents, SiO2,Al2O3, total iron as Fe2Og, TiOg, 

MnO, FgOs, CaO, MgO, Na2O, and K«jO. (See fig. 1.) 

The accuracy and precision of the results obtained by 

the methods described are less than that which would 

be expected to be obtained by competent analysts 

carefully using the classical or conventional methods.

Nevertheless, the rapid methods of analysis should 

be applicable to the analysis of a large number of 

samples which would ordinarily be analyzed by 

classical methods.

The methods describee! in this paper are rapid, 

simple, direct, and are less subjective than conventional methods. For these reasons it is easy to 

establish the reliability of the Results obtained.

The rapid procedures can be easily learned and 

carried out by personnel with considerably less 

training than that required for analysis by classical 

methods. IMs practicable for one person using the 

schedule suggested below, to analyze approximately 

sixteen silicate rock samples each five day week.

For the sake of simplicity, the procedures for 

preparation of sample solutions and for the various
amm. 

molybdate

etc.

Fuse

SOLUTION A

Sample

HF-H2S04

Fume

SOLUTION B

Vanadomolybdate

etc.

PH

Figure 1. --Flow diagram for rapid analysis of silicate rocks.
determinations describe the analysis of a single sample. 

Large numbers of samples can be most efficiently 

analyzed in batches of six to twelve samples at a time. 

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.

SPECIAL APPARATUS

Most of the apparatus used in the procedures 

described in this paper is usually 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, together with the spectrophotometer and flame photometer described below.

In the preparation of solutions for determination 

of SiC>2 and.AL>O3, ^ne samPles are fused in covered 

nickel crucibles of approximately 75 ml capacity.

In some procedures the use of polyethylene 

bottles or vycor beakers or flasks is advised for 

storing solutions, to avoid contamination which might 

result from use of ordinary glassware.

Spectrophotometer

All spectrophotometric measurements were 

made with a Beckman Model B Spectrophotometer. 

Nevertheless the methods can be readily adapted to use 

other good quality spectrophotometers. Only one 

phototube was employed for the measurements, all of 

which were made in the range, 320 to 700 m mu.

To insure the stability of the source of illumination 

a storage battery is used. The amplifier circuit of the 

instrument is fed by a - c line current.

As it is desirable to measure colors of low intensity accurately, test tubes having a diameter of 

about 27; 5 mm are used instead of tubes of smaller 

diameter which are more commonly used. The simple 

adaptor shown in figure 2 was built to support these tubes 

in the instrument. Care must be taken to insure that the 

adaptor is rigidly fixed in the Spectrophotometer, as 

slight shifts in position cause large changes in the 

fraction of incident light reflected from the test-tube 

surface, The comparison tubes should be carefully 

matched using a colored solution, and marked so that 

they can always be placed in the carrier in the same 

position. A commercial adaptor which accommodates 

tubes of smaller diameter may be purchased for the 

instrument, but the adaptor described here in which 

comparison tubes with longer path length can.be used 

is more satisfactory.

The Spectrophotometer is operated as follows: 

Insert a comparison tube containing a reference blank 

solution in the tube adaptor. Set the wave-length 

selector to the desired wave length, the sensitivity 

switch to position 1, and open the phototube shutter. 

Adjust the meter to read 100 percent transmittance by 

varying the slit width. Then replace the comparison 

tube containing the reference-blank Solution with one 

containing the sample solution. Open the shutter and 

observe the meter reading. If the reading is less than

31. 5 percent, turn the sensitivity switch to the position 

which gives a reading greater than 31. 5 percent 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.

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 which was derived by use of the 

equation: A = 2 - log T. All calculations are then 

made with the absorbance values. Absorbance values 

are easier to use than percent transmittance values 

because, when Beers' 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 the 

particular instruments 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 changes. A special glass atomizer 

shown in figure 3 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 atomizer shown 

has certain advantages over the funnel-type atomizer 

when used with the flame photometer in the determination of Na^O and K>>O 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 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 deliberate 

rinsing and flushing, needed in using the funnel type of 

atomizer, is unnecessary.

Two pressure regulators, installed in the gas 

line, give a more steady burner flame by reducing 

fluctuations in the gas pressure.

To start operation of the flame photometer for 

the determinations Na£O and KoO, first turn the 

electric switch on the panel of the instrument to the 

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

in 2, open the main valve on the propane tank, set the 

gas regulator which is nearest the main valve to 10 Ibs 

in^, 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
Notes:

All joints butt-soldered 

Entire piece to be painted

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Figure 2. --Test tube adaptor for the spectrophotometer.

4
Table 1. Conversion of percent transmission (r) to absorbance (A)

T

50.0

50-5

51.0

51-5

52.0

52.5

55.0

53.5 

54.0

54.5

55-0

55-5

56.0

56.5

57-0

5g!o

58.5

59.0

59-5

40.0

40.5

41.0

41.5'

42.0

42.5 '

45.0

45.5

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

0.525

.516

 509

.502

.482

.475 

.469

.462

.456

.450

.444

.458

.452

.426 

.420

.415

.409

.405

.598

.595

.582

.577

.572

* 567

.562

.557

 552

.547

.542

.557

 553

.528

 525

.519

.514

.510

.505

T

50.0 50.5

51.0 51.5 -

52.0 52.5

55.0 '

55.5 54.0 '

54.5

55.0

55-5

56.0

56.5

57.0

57-5 5§.0

58.5

59.0

59-5

60.0

60.5

.61.0

61.5

62.0

62.5

65.0

65.5

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

0.501

.297

 !288

.284

.280

.276

.272 

.268

.264

' .260

.256

.252

.248

.244

.240 

.257

 235

.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

75.0 '

75-5 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

85.0

85.5

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

.145

.140

.137

.134

!l28

.125

.122

.119

.116

.114

.111 

.108

.105

.102

.100

.097

.094

.092

.089

.086

.084

.081

. .078

.076

.073

.071

.068

.066

.065

.060

.058

. .056

-055

.051

.049

T

90.0 90.5

91.0 91.5

92.0

92.5

95-0 95.5 - 

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

.045

.041

.059

.036

.034

.032

.029 

.027

.025

.022

.020

.018

.016

.013

.011 

.009

.007

.004

.002

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 min before readings are taken.

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. 1. ) Solution A is used in the determination of SiO2 and A12O3. It is prepared by fusing 

0. 1000 g of the sample, with NaOH in a nickel crucible. 

In this way complete decomposition of the sample 

is obtained very quickly at a comparatively low 

temperature. The nickel crucible is only slightly 

attacked, and the nickel taken into solution does not 

interfere with the subsequent determination of SiO2 

and

K2O. To prepare this solution, a 1.000 g sample is 

digested, with HF and H2SO4 in a large platinum 

crucible, over night, on a steambath. HF is removed 

by heating until copious fumes of SOg 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 

KoO, should be withdrawn immediately after preparation of the solution. Na^O and K2O should then be 

determined immediately, or the aliquots should be 

stored in plastic, vycor, or platinum containers.

Solution B is used in the determinations of 

TiO2 , total iron, MnO, F2O5, Mg, CaO, Na2O, and

Reagents

NaOH, pellets, A.C.S. grade. Store in 

plastic bottle to prevent contamination 

that might result from attack on the 

glass of the reagent bottle when pellets 

absorb moisture from the air.

HF, 48 percent 

H2SO4, 1+1
Tube for liquid 

(capillary tubing)

Avoid enlar^in^ I.D. of 

capillary at this joint

Tube for air 

(capillary or regular tubing)

I.D. 3mm ±.25mm

fire polished

rorifice I.Omm ±.2mm

orifice 20mm ± .02mm

O.D. at tip l-2mm

tip bevelled and 

fine-ground

3cm

Figure 3. --Special glass atomizer for the flame photometer.

6
Solution A DETERMINATION OF

1. Weigh accurately 0.1000 g of sample, ground 

to pass a 100 mesh screen. Transfer to a nickel 

crucible of approximately 75 ml capacity.

2. Add 10 pellets (approximately 1. 5g) of NaOH.

3. Cover the crucible and heat to dull red for 

3 to 5 min. Remove from the heat and swirl the melt 

around the sides of the crucible. Allow to cool.

4. Add approximately 50 ml of distilled water 

and allow to stand at least 15 to 20 min, stirring 

occasionally with a platinum rod.

5. Transfer the contents of the crucible to 

a 600 ml beaker containing approximately 400 ml of 

distilled water and 6 ml of HC1. Scrub the crucible 

with a rubber policeman and wash any remaining 

solution or residue into the beaker.

6. Transfer the solution to a 1 liter volumetric 

flask, make up to volume with distilled water and mix 

well.

Solution B

1. Transfer a 1. 000 g sample to a platinum 

crucible of approximately 100 ml capacity.

2. Add 10 ml of 1+ 1 H2SO4.

3. Add approximately 20 ml of HF.

4. Cover the crucible and digest overnight on a 

steambath.

5. Remove the cover, rinse and allow the 

crucible to heat on the steambath until the volume of 

the solution is reduced to approximately 5 ml.

6. Place the crucible over an electric heater 

or gas burner and heat until strong SOo fumes evolve.

7. Allow the crucible and contents to cool.

8. Fill the crucible with distilled water.

9. Cover the crucible and digest on the steambath until the residue dissolves. If a residue remains 

after digesting for approximately one-half hour, 

transfer solution and residue to a 400 ml vycor 

beaker and boil gently for 10-15 min. If a small 

amount of insoluble material still remains, it may be 

barium sulfate, zircon, or possibly tourmaline. This 

may be filtered off and discarded, because BaO and 

ZrOo are not determined. Tourmaline is found, but 

rarely in more than trivial quantities.

10. Transfer the solution to a 200 ml volumetric 

flask, make up to volume and mix well.

11. Immediately withdraw 50 ml of the solution 

with a pipet and transfer tp a 200 ml volumetric flask 

if K^O and Na£O can be determined the same day or, 

if K2O and NagO cannot be determined the same day, 

transfer the aliquot to a plastic, platinum, or vycor 

container to eliminate the possibility of alkali contamination from the container.

In the determination of SiO^ (Bunting, 1944) the 

yellow silicomolybdate complex is reduced to molybdenum 

blue and the transmission of light is measured at 

650 m mu. As silica is the predominant constituent 

in silicate rocks, relatively more precise values are 

desired for SiOo than for the constituents present in 

lower concentrations. For this reason sample weighing, 

volume measurements, and spectrophotometer 

readings must be made very carefully.

REAGENTS

Ammonium molybdate reagent solution: Dissolve 75 g. 

ammonium molybdate in 750 ml of water. Add 

100 ml of 1+1 HgSO4 and make up to one liter 

volume. Store in a plastic bottle.

Tartaric acid solution, 10 percent: Water solution 

stored in a plastic bottle, 500 ml.

Reducing solution: Dissolve 7 g of sodium sulfite in 

water. Add 1. 5 g of l-amino-2-naphthol-4- 

sulfonic acid and stir until dissolved. Dissolve 

90 g of sodium bisulfite in 800 ml of water and 

add this solution to the solution above and mix.

Reference standard solution: A solution is prepared 

by the method described above under "Preparation of sample solution, Solution A" using the 

National Bureau of Standards standard sample 

no. 70 or no. 99. The nickel crucible should 

be carefully cleaned with dilute HC1 before use 

to remove any iron which may have been left 

on the crucible from the previous fusion. The 

standard solution should be stored in a plastic 

bottle and should be prepared fresh if more than 

one week old.

PROCEDURE

1. Withdraw 50 ml of sample solution A, and 

50 ml of the reference standard, with a pipet, and 

transfer each aliquot to separate 500 ml volumetric 

flasks. Make the solutions, up to volume with distilled water and mix well.

2. Withdraw 50 ml of each solution from step 1 

with a pipet and transfer to separate 100 ml volumetric 

flasks.

3. Add approximately 50 ml of distilled water 

to another 100 ml flask to be used for preparation of 

the reagent blank solution.

4. Add 1 ml of the ammonium molybdate reagent 

to each flask, swirling the flasks during the additions. 

Mix well and allow to stand for 10 min.

5. Add 4 ml of the tartaric acid solution, 

swirling the flasks while adding.

6. Add 1 ml of the reductant solution while 

swirling the flasks, make to volume, mix well, and 

allow to stand at least 30 min.

7. Determine the percent transmission for 

each solution at 650 m mu using the reagent blank 

solution as the reference blank solution.
CALCULATIONS

1. Convert each of the values obtained for 

percent transmission to absorbance using table 1.

2. Compute the factor:

Percent SiOg of comparison standard 

absorbance of comparison standard Factor

3. Compute percent SiOg in samples:

Factor x absorbance of sample solution ~ Percent SiOz

DETERMINATION OF A12O3

AlpOq is determined by measuring the transmission of light, at 370 m mu of the complex of 

aluminum with ferron (8-hydroxy-7-iodo-5-quinoline 

sulfonic acid, (Davenport, 1949).

Iron and titanium also form complexes with 

ferron which affect the absorbance at 370 m mu. The 

effects are proportional to their respective concentrations and are additive so it is possible to apply 

corrections for them. The correction for TiOo is 

based on the concentration of TiOg in the sample as 

determined in the section "Determination of TiOg". 

The correction for iron is based on the determination 

of the effect of the iron actually present in the solution 

used in the determination of AloOo. This is necessary 

because of the partial retention of iron by the nickel 

crucible used for the NaOH fusion. The effect of the 

iron actually present in the solution can readily be 

determined because it is the only common ion complexed by ferron which has appreciable absorbance 

at 600 m mu and the relationship of concentration 

of iron to absorbance is linear at both 3YO m mu and 

600 m mu.

REAGENTS

Ferron (8-hydroxy-Y-iodo-5-quinoline sulfonic acid) 

solution, . 2 percent: water solution, 1000 ml.

Ammonium acetate solution, 10 percent: water 

solution, 1000 ml.

HC1, 1+9 solution:

Standard Fe solution: Prepare a solution in which 1 ml 

contains 0. 01 mg of FeoO3 by diluting 10 ml, 

of the standard iron somtion, FegOg = 0. 5 mg/ml 

described under "Determination of total iron as 

FeoOg, Reagents", to 500 ml with water.

Standard TiO2 solution: Dilute 10 ml of the standard 

)o solution described under "Determination of 

" ?, Reagents" to 500 ml with water. The 

)g concentration is equivalent to that of a 

solution prepared from sample containing 2 percent TiOp when the procedure below is followed.

Reference standard solution: The "reference standard 

solution", prepared for the "Determination of 

SiOo" and described under "Reagents", is used.

PROCEDURE

1. Transfer 10 ml of solution A , 10 ml of the 

reference standard solution, and 10 ml of the standard 

solution to separate 100 ml volumetric flasks.

For the first set of samples, and occasionally thereafter, 10 ml of the standard TiOg solution is also 

carried through the procedure.

2. Dilute the solutions in the flasks to approximately 70 ml. Add approximately YO ml of distilled 

water to another 100 ml volumetric flask to be used 

for the preparation of a reagent blank solution.

3. Add 1 ml of HC1 (1+9) to each flask and mix.

4. Add 10 ml of the ammonium acetate solution 

to each flask while swirling the flask.

5. Finally, add 10 ml of the ferron solution 

while swirling the flask. Make up to volume, mix well, 

and allow the solutions to stand at least 1 hr.

6. Transfer 50 ml of each solution to comparison 

tubes and determine percent transmission at 3YO m 'mu, 

using the reagent blank solution as the reference blank.

7. Determine percent transmission at 600 m mu 

for each solution, except the reference standard 

solution and the solution containing the standard TiOg, 

using the reagent blank solution as the reference blank.

CALCULATIONS

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

2. Calculate the factor for the iron correction:

absorbance af standard FeaQ3 at 370 m mu . Ft>iQg correction facter. 

absorbance af standard FejOs at 600 m mu

3. Calculate the corrections for iron effect:

The iron correction - Fe 20a correction factor x absorbance of sample 

solution at 600 m mu * absorbance at 370 m mu due to iron.

if standard TiOp solution was run:

4. Calculate the correction factor for TiOg, 

solu

2.00 factor for TiO

absorbance of standard TiOs solution at 370 m mu

5. Calculate the corrections for TiC^ effect 

using the factor (step 4) or use the factor previously 

determined:

TiOa - concentrotion of TiOg in sample solution 

correction factor

6. Subtract the sum of the FeoO3 and TiOo 

corrections from the absorbance values obtained for 

the sample solution at 370 m mu.

7. Calculate the factor for AlgOg:

Concentrotion AlgOa in reference standard a faffa 

absorbance at 370 m mu

8. Calculate percent A12O3

factor x corrected absorbance (step 7} = percent A1 2 03

9. Should the AlgOs be greater than 25 percent, the determination should be repeated using 

5 ml of solution A and calculations should be 

made accordingly.
DETERMINATION OF TOTAL IRON AS FegOg

Total iron is determined by measuring the transmission of light at 440 m mu of the yellow ferric 

chloride complex in 1+ 1 HC1 (Finsl, 1944). The 

color intensity is appreciably affected by temperature 

and acid concentration. Errors due to these effects 

can be satisfactorily controlled by running standard 

solutions of ferric iron simultaneously with each set 

of sample solutions and using aliquots of the same 

1+ 1 HC1 for both sample and standard solutions. 

The procedure is very simple and rapid.

REAGENTS

1+ 1 HC1: Mix 1 liter of HC1 and 1 liter of distilled 

water and allow to come to room temperature 

before using.

Standard iron solution, FegOg = Q. 5 mg/ml: Weigh 

0. 699 g of pure iron wire. Dissolve in 50 ml 

of 1+ 1 HC1. Add 50 ml of HgSO4. Evaporate 

and heat to fumes of SOg, adding approximately 

1 ml of HNOo as the fuming point is approached. 

Cool, dilute to 200 ml, and heat until solution is 

clear. Cool and make up to 2 liters with distilled water. The iron concentration in this 

standard is equal to that of a solution prepared 

as directed under "Preparation of sample solution, 

Solution B " from a sample containing 1.0 percent 

total iron as FegOg.

Standard iron solution, Fe^Oo = 0. 25 mg/ml: Make 

500 ml of the standara iron solution containing 

0. 5 mg Fe20g/ ml to 1 liter with 2. 5 percent 

112804. The iron concentration in this standard. 

is equal to that of a solution prepared as directed 

under "Preparation of sample solution, Solution B" 

from a sample containing 5 percent total iron as 

Fe203.

PROCEDURE

1. Add exactly 25 ml of the 1+ 1 HC1 to a comparison tube for the sample, to two tubes for standards, 

and to another tube for the reagent blank solution.

2. Add 5 ml of solution B to one of'the tubes 

containing the 1+1 HC1 and mix well.

3. Add 5 ml of standard iron solution, Fe2Og = 

0. 5 mg/ml and 5 ml of standard iron solution, 

Fe2Og = 0. 25 mg/ml to tu6es containing the 1+ 1 HC1 

and mix well.

4. Add 5 ml of distilled water to another of the 

tubes containing 1+1 HC1. This will be the reagent 

blank solution.

5. Determine the percent transmission at 

440 m mu for the sample and standard solutions using 

the reagent blank as the reference blank solution.

CALCULATIONS

1. Convert the readings obtained for percent 

transmission to absorbance using table 1.

CALCULATIONS-Continued.

2. Compute a factor for each standard solution:

TO

absorbance ol 0.5 mg/m |) " facto

absorl 0.25 ma/m|) facto

3. Compute percent total iron as FeoOq using 

the average of the factors (step 2) .for the factor:

Factor X absorbance of sample solution ~ percent total iron as Fe 2 0 3.

If percent Fe2Og in the sample is desired it is calculated in the usual way by subtracting the Fe2Oo 

equivalent of FeO (separately determined) from percent 

total iron as Fe2Og.

DETERMINATION OF TiO2

TiO2 is determined by an adaptation of the wellknown peroxide procedure. It is common practice 

in conventional procedures to determine TiO2 on the 

R2Og group precipitate. In the method described 

here the determination is made without separations by 

developing the yellow titanium peroxide on ah aliquot 

of a solution of the original sample and measuring 

the transmission of light at 400 m mu.

REAGENTS

TiO2 reagent solution: Add 100 ml 1+ 1 H2SO4, 100 ml 

H3PO4, and 100 ml of 30 percent H2O2 to 700 ml 

of water, mix and store in a brown bottle.

Standard TiOr, solution: Weigh 0. 1013 g of National 

Bureau of Standards standard titanium dioxide 

no. 154 in a small platinum crucible. Add 1 g 

of sodium bisulfate and fuse. Allow to cool and 

place crucible in a beaker containing 50 ml of 

1+1 HVjSO^.. Heat until melt completely dissolves. 

Cool and make the solution to 1 liter, with distilled water, in a volumetric flask. Store in a 

1 liter glass-stoppered bottled. The TiO2 

concentration is equal to 0. 1 mg per ml or to 

that of a solution prepared as directed under 

"Preparation of sample solution Solution B", 

from a sample containing 2. 00 percent TiOr,.

PROCEDURE

1. Transfer a 15 ml aliquot of solution B to a 

comparison tube. A 15 ml aliquot of the standard TiO2 

solution is run with the first set of sample solutions 

and occasionally thereafter to determine the factor 

for

Percent TiOg 

absorbance

2. Transfer 15 ml of distilled water to a 

comparison tube for use in preparing a reagent blank 

solution.

3. Add 15 ml of TiOr, reagent solution to each 

tube and mix well.
4. Determine the percent transmission of each 

solution at 400 m mu, using the reagent blank solution 

as the reference solution.

CALCULATIONS

1. Convert each of the values for percent 

transmission to absorbance using table 1.

2. Compute the factor if a standard solution was

run:

2.00

absorbance of standard solution factor

3. Compute percent TiC>2 using the factor 

calculated (step 2) or use the factor as previously 

determined:

factor x absorbance of sample solution = percen

DETERMINATION OF P2O5

Pr>O5 is determined by measuring the light 

transmitted, at 430 m mu, by the yellow molybdivanodphosphoric acid complex (Kitson and Mellon, 1944). 

The simplest conventional procedures involve precipitation as phosphomolybdate, filtration, and either 

titrating or drying and weighing the precipitate. The 

procedure employed here, which is much simpler, 

requires only the mixing of reagent and sample 

solutions and determination of percent transmission.

REAGENTS

reagent solution: Dissolve 1. 25 g of ammonium 

metavanadate in 400 ml of 1+1 HNOg. Dissolve 

50 g of ammonium molybdate in 400 ml of water. 

Mix the solutions and make up to a liter volume 

with distilled water.

Standard ?2O5 solution: Weigh 0. 0849 g of National 

Bureau of Standards standard phosphate rock 

sample no. 120. Transfer to a 150 ml beaker 

and add 25 ml of 1+1 HNOs. Digest on a steambath until solution is essentially complete. Cool 

and make up to 1 liter volume in a volumetric 

flask. Store in a glass -stoppered bottle. The 

concentration of P^^^ is equal to that of a 

solution prepared, as directed under "Preparation 

of sample solution, Solution B, " from a sample 

containing 50 percent PO^RPROCEDURE

1 . Transfer a 25 ml aliquot of sample solution 

B to a comparison tube. A 25 ml aliquot of the standard 

p£C5 solution is run with the first set of sample 

solutions and occasionally thereafter to determine the 

factor for

Percent P g Q 8 

absorbance

2. Transfer 25 ml of water to a comparison 

tube. The resulting solution, after being treated the 

same as the sample solutions, will be used as a reference blank solution.

3. Add 10 ml of reagent solution to each comparison tube, swirling the tube during the addition. 

Mix and allow to stand for at least five minutes.

4. Determine the percent transmission, at 

430 m mu, 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 if the standard solution was

_______0.50_______ 

absorbance of standard solution 'actor

run:

3. Compute percent Fo^S usin9 tne 

calculated above (step 2) or use the factor previously 

determined:

foctor x absorbance = percent PS Os 

DETERMINATION OF MnO

MnO is determined by measuring' the light 

transmitted at 525 m mu, by an aliquot of sample 

solution in which the manganese has been oxidized 

to permanganate with KIO4.

REAGENTS

H2SO4 1+9, H3PO4 , KIO4.

Standard MnO solution: Weigh 0. 0552 g of National 

Bureau of Standards standard manganese ore 

no. 25b. Transfer to a 250 ml beaker and add 

25 ml of 1+ 1 HNOg and 2 to 3 ml of 3 percent 

^2^2' Digest on a steambath until no black 

residue remains. Cool and add 50 ml of H2SO4. 

Evaporate and continue heating until fumes of,. 

SOo evolve. Cool and dilute to approximately 

200 ml volume. Cool and make up to 2 liter 

volume. Store'a liter of the solution in a glass 

stoppered bottle. The MnO concentration is 

equal to that of a solution prepared as directed 

under "Preparation of sample solution solution B" 

from a sample containing 0. 50 percent MnO.

PROCEDURE

Transfer a 20 ml aliquot of solution B to a 100 ml 

beaker. For the first set of. determinations and 

occasionally thereafter 20 ml of the standard MnO 

solution is run with the sample solutions to determine 

the factor .

percent Mno 

absorbance

2. Add 25 ml of 1+ 9 HgSO4.

3. Add 0. 5 ml HgFO4.

4. Add approximately 0. 2 g of KIO4.

5. Heat the solutions and keep at near boiling 

temperature for at least 10 min.

10
6. Cool the solutions to room temperature in a 

water bath.

7. Transfer the solutions to 100 ml volumetric 

flasks, make up to volume, and mix well.

8. Determine the percent transmission for each 

solution at 525 m mu, using water as the reference.

CALCULATIONS

1. Convert each of the values for percent 

transmission to absorbance using table 1 above.

2. Compute the factor if a standard was run: 

0.50

absorbance of standard solution facto

3. Compute percent MnO using the factor calculated (step 2), or use the factor as previously 

determined:

factor x absorbance of sample solution - percent MnO.

DETERMINATION OF CaO

CaO is determined by titration with sodium 

versenate solution (disodium ethylenediamine 

tetraacetate) using murexide (ammonium purpurate) 

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

aluminum in appreciable quantities interfere with the 

determination and must be removed.

REAGENTS

NaOH, 10 percent: 500 ml water solution stored in 

a plastic bottle.

Murexide or ammonium purpurate reagent: A small 

scoop which holds approximately 0. 2 g of 

indicator is used for measuring the reagent.

Standard CaClg solution: Weigh 0. 8925 of dry Ca.CO%. 

Transfer to a 150 ml beaker. Add 50 ml of 

water and then add dilute HC1 slowly until all 

of the CaCOs is dissolved. Boil for a few 

minutes. Cool and transfer to 1 liter volumetric 

flask and make up to volume. One ml contains 

CaClg equivalent to 0. 5 mg CaO.

Standard versenate solution: Weight 2. 5 g of disodium 

ethylenediamine tetraacetate and 0. 1 g 

MgCl2. 6H2O. Dissolve in 2 liters of distilled 

water. Standardize the versenate solution by 

titrating several 10 ml aliquots of the standard 

CaClg solution using the procedure described 

below. (Steps 6 and 7.)

PROCEDURE

1. Transfer a 50 ml aliquot 

a 250 ml beaker.

of solution B to

2. Dilute to approximately 200 ml with distilled 

water.

3. Insert the electrodes of a pH meter and add 

NH4OH (1+ 1) dropwise from a buret until the meter 

reads pH 4. 8 to 5. 1.

4. Wash the contents of the beaker into a 250 ml 

volumetric flask. Do not police the beaker. Make 

to volume and mix.

5. Four the contents of the flask through a dry 

filter paper, in a dry funnel, into a dry beaker using 

Whatman no. 40 12. 5 cm paper. Filter approximately 

200 ml of the solution. The filtrate is used for both 

CaO and MgO determinations.

6. Transfer 50 ml aliquots from the beaker to 

2 porcelain 350 ml casseroles. Into a 150 ml beaker 

place approximately 100 ml of water, 10 ml of 10 percent NaOH and 2 scoops (0. 4g) calcium indicator. 

Transfer 50 ml of this mixture to each of the 2 

casseroles, with a graduate.

7. Titrate as follows: Use two 50 ml burets 

side by side filled with standard versenate solution. 

A daylight fluorescent lamp supported over the 

casseroles'is a good source of illumination. Add 

the versenate solution to one casserole, which serves 

as the color reference, until the end point is clearly 

passed. The color does not change beyond the end 

point so the solution in the second casserole can now 

be titrated carefully to match the color of the first. 

The second titration is recorded.

CALCULATIONS

1. Calculate the percent CaO:

Volume of titration (ml) x CaO equivalent (mg CaO per ml versenage) x 2 = 

percent CaO.

DETERMINATION OF MgO

MgO is determined by titration with sodium 

versenate solution using Eriochrome Black T (Betz 

and Noll, 1950). By this method the total calcium 

plus magnesium is titrated and MgO is calculated 

after subtracting the volume of sodium versenate 

solution equivalent to the calcium.

REAGENTS

Eriochrome Black T reagent: Water solution, 0. 1 g 

of the pure dye in 50 ml. This solution should 

be prepared fresh each day.

Titration buffer solution: Dissolve 70g of NH^Cl in

600 ml of concentrated NH4OH and dilute to 1 liter 

with distilled water.

Standard sodium versenate solution: Titrate 10 ml 

of the standard calcium chloride described 

under "Determination of CaO, Reagents" with 

the standard sodium versenate solution also 

described under "Determination of CaO, Reagents" 

using the Erischrome Black T reagent, by the 

method described below. Compute the CaO 

equivalent per ml of solution. Titrate 25 ml 

of the standard MgClo solution described below 

with the same standard sodium versenate 

solution by the method described below. 

Calculate the MgO equivalent per ml of solution.

Standard MgClg solution: Weigh 0.1206 jpure magnesium 

ribbon. "Dissolve in a few ml'of dilute HC1 in

11
a beaker. Evaporate to dryness. Dissolve in 

distilled water and make up to 2 liters in a 

volumetric flask. Store in a pyrex bottle. One 

ml contains MgCl2 equivalent to 0. Img MgO.

PROCEDURE

1. Transfer a 50 ml aliquot of the solution from 

which R2Og 'aas been removed ("Determination of 

CaO, step 5") to a 400 ml beaker.

2. Add approximately 250 ml of distilled water.

3. Add 10 ml of the titration buffer solution.

4. Add 0. 5 ml of Eriochrome Black T indicator.

5. Titrate with standard sodium versenate until 

the red color of the solution changes to blue. A 

titration illuminator and electric stirrer as described 

under apparatus are very helpful in this titration.

CALCULATIONS

1. To obtain the volume of standard versenate 

consumed by the CaO for the sample solution, multiply 

the ratio of the CaO equivalent obtained for the 

versenate solution using murexide indicator ("Determination of CaO, Reagents, Standard versenate 

solution") to the CaO equivalent for the same versenate 

solution when Eriochrome Black T indicator was used 

("Determination of MgO, Standard versenate solution") 

by the volume of versenate used in the determination 

of CaO in the sample ("Determination of CaO", step 4):

CaO equivalent with Murexide______

CaO equivalent with Eriochrome Black T x *«"pl« titration with murexide =

volume of versenate consumed by 

CaO in sample solution

2. Calculate the volume of versenate consumed 

by MgO:

(sample titration, Eriochrome Black T indicator) - (volume of versenate 

consumed by CaO) = volume of versenate consumed by MgO.

3. Calculate percent MgO in samples:

volume of versenate consumed by MgO x MgO equivalent (mg Mgo per 

ml versenate x 2) = percent MgO

DETERMINATION OF KgO AND Na20

K20 and Na2O are determined by a flame photometer method in which lithium is used as an internal 

standard (Brannock and Berthold, U. S. Geol. Survey 

Bull., in press). Iron, aluminum, and calcium, 

which affect the results, are removed before introduction of the internal standard.

The use of an internal standard reduces the 

effect on results for KoO and Na^O due to differences 

in concentration of dissolved salts and differences in 

viscosity between standard and sample solutions as 

well as reducing 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 K20 or NarjO in the standard and sample 

solutions is essentially linear.

REAGENTS

K2S04 , Na2S04 , Li2SO4 , (NH4) 2SO4, all A. C. S. 

grade.

Stock solution of KpSO. containing 1. 156 g of dry

K2SO4/1 which is^ equivalent to 0. 25 g K20/400 ml. 

Prepare 2 liters.

Stock solution of NagSO4 containing 1. 432 g of dry 

Na9SO4/l which is equivalent to 0. 25 g Na20/ 

400 ml. Prepare 2 liters.

Stock solution of Li2SO4 containing 15. 84 g of

Li2SO4/l which is equivalent to 2000 ppm lithium 

concentration. Prepare 8 liters or more.

Standard solutions equivalent to . 5, 1, 2, 4, 6, 8, 10 

and 12 percent K20 respectively each containing 

100 ppm lithium and 2 percent (NH4)pSO4 are 

prepared by diluting 5, 10, 20, 30, 40, 60, 80, 

120 ml of stock solution of KoSO/ plus 50 ml 

of stock LigSO4 and 20 g of (NH4)2SO4, in each, 

to I liter with distilled water in a volumetric 

flask.

Standard solutions of similar concentrations to those 

for K2O are prepared, for Na2O, in the same way 

using the stock Na2SO4 solution and the stock 

Li2SO4 solution.

Internal standard solution in which the concentration 

of lithium is 200 ppm is prepared by diluting 

200 ml of the stock solution of LigSO4 to 2 

liters with distilled water.

Solution of (NH4)£SO4, 25 percent, prepared by

dissolving 4bO g of (NH4) 2SO4 and making up to 

2 liters with distilled water.

PROCEDURE

1. Light the burner of the flame photometer and 

adjust the flame as described under special apparatus, 

Flame photometer.

2. Turn the electric switch on the panel of the 

flame photometer to the "on" position.

3. Transfer 50 ml of solution B above to a 

200 ml volumetric flask.

4. Add 20 ml of 25 percent ammonium sulfate 

solution to the flask and dilute to 150 to 175 ml with 

distilled water.

5. Add NH4OH (alkali free) to the solution in 

the flask until a slight excess is present as indicated 

by the color change of a small piece of litmus paper.

12
6. Then add approximately 1 ml of freshly prepared concentrated ammonium carbonate solution.

7. Make the solution up to 200 ml with distilled 

water and mix well.

8. Filter 75 to 100 ml of the solution through 

dry 12. 5 cm Whatman no. 40 dry filter, in a dry 

funnel, into a dry pyrex bottle or beaker.

9. Withdraw 50 ml of the filtrate with a pipet 

and mix with 50 ml of lithium sulfate solution, 

containing 200 ppm lithium, in a pyrex beaker or 

bottle. The solution is now ready for determination 

of K>>O and Na2O by the flame photometer.

10. If the approximate concentration of potassium 

in the sample solution can be estimated, omit steps 

10-13 and proceed with step 14. If the approximate 

concentration of potassium in the sample solution 

cannot be estimated, pour 15 to 20 ml of standard 

potassium sulfate solution, in which the potassium 

sulfate concentration is equivalent to 12 percent K^O, 

into a 30 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.

11. With the same solution (step 10) 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 

facial tissue.

12. Put 15 to 20 ml of the sample solution (step 9) 

in a 30 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.

13. Assume the recorded readings to be proportional to concentration of potassium in standard and 

sample solutions and calculate the approximate concentration of potassium as KgO.

14. Repeat step 11 for the sample solution using 

the standard solution with the nearest higher concentration to the estimated concentration of potassium 

in the sample solution.

15. Repeat step 12.

16. Repeat step 12 using the standard solution 

with the nearest lower potassium concentration to the 

estimated concentration of potassium, in the sample 

solution, instead of the sample solution.

17. With the same solution (step 16) 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.

18. Repeat step 12.

19. Repeat step 12 using the higher standard 

instead of the sample solution.

20. NaoO is determined on a portion of the same 

sample solution which was used for the determination 

of K2O (step 10). The element selector is set to the 

position of maximum response for sodium and the 

NaoO is determined in the same way as K^O.

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.

x = concentration of K 20 in the sample solution

y = dial reading for the sample solution 

xi = concentration of KaO in the lower standard solution 

yi - dial reading for the lower standard solution 

x2 = concentration of K 20 in the higher standard solution 

y2 ~ dial reading for the higher standard solution

DETERMINATION OF FeO

Ferrous iron is determined by -the conventional 

titrimetric method using standard dichromate solution 

with diphenylamine sulfonic acid as the indicator. 

When decomposition is carried out on batches of 

approximately eight samples simultaneously the time 

consumption per sample is small.

REAGENTS

H2SO4, 48 percent HF, all A. C. S. grade.

H2SO4 1 + 3

Diphenylamine sulfonate indicator: Dissolve 

0. 2g of sodium diphenylamine sulfonate in 1 

liter of water. Add 1 liter of 85 percent H3PO4 

and mix well.

Standard dichromate solution: Weigh 2. 808 g of 

dry National Bureau of Standards potassium 

dichromate or other pure dry potassium 

dichromate and make up to 2 liters in a volumetric 

flask. 1 ml = 2. 000 mg FeO.

PROCEDURE

1. Weigh 0. 5000g of sample and place in 

platinum crucible of approximately 100 ml volume.

2. Add 20 ml of 1+3 J^SO^ to the crucible, 

cover and carefully bring to a bou over a gas burner 

or an electric heater.

3. Add 5 to 8 ml of HF. 

boil. Boil gently for 15 min.

Cover and bring to a

13
4. While the solution in the crucible is boiling 

add 400 ml of water and approximately 10 g of boric 

acid to an 800 ml 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 min, 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 

prior to 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 sec.

CALCULATIONS

1. Compute percent FeO in the sample:

ml dichromate x 2.000 inn =

500 

ml dichromate x 4 = Percent FeO

PROCEDURE

1. Ignite, cool, and weigh a platinum or porcelain crucible of 20-30 ml capacity.

2. Add 'approximately 1 g of sample and weigh 

the crucible plus sample.

3. Heat over a low burner flame at first and 

gradually bring to full heat of the burner.

4. Heat at full heat of a Fisher burner for 1 

,hr or transfer to a muffle furnace and heat for 1 hr 

at 1000 C.

5. Allow the crucible and contents to cool in 

a desiccator.

6. Weigh the crucible and contents. 

CALCULATIONS

1. Calculate the percent loss on ignition:

Loss in weight x 1QQ = Percent loss on ignition, 

sample weight

DETERMINATION OF LOSS ON IGNITION

The results obtained for loss on ignition can be 

used, after applying corrections for the oxidation 

of divalent iron, for estimating the amount of CO2 

plus H2O in the samples. Divalent iron is not always 

completely oxidized so, when the sample contains 

appreciable FeO, the value for CO2 plus ^O may be 

in error.

EXPERIMENTAL RESULTS

The methods described have been tested by 

analyzing twelve synthetic samples prepared by mixing selected National Bureau of Standards standard 

samples. The mixed samples have been prepared to 

include as nearly as possible the ranges of concentrations, of the above mentioned constituents, 

which might be expected to be found in typical silicate 

rocks. In table 2 is shown the percentage of each of

Table 2. Percentage composition of National Bureau of Standards (K.B.S.) standard

samples in the mixture samples.

National Bureau 

of Standards 

sample no .

Quartz

la Limestone

26 Crescent 

iron ore

69 Bauxite

70 Feldspar

88 Dolomite

97 Clay

98 Clay

99 Feldspar

102 Silica b.rick

120 Phosphate 

rock

A

U

U

U

1

B

49

49

2

C

10

29

50

10

1

D

58

14

47

1

E

19

9

65

7

P

9

66

19

6

G

5

55

'57

1)

H

50

7

59

4

I

50

50

J

50

50

K

50

50

L

50

50

14
Table 3. Results obtained for National Bureau of Standards (N.B.S.) mixture

samples

.: 

SiOo

A120"*

Fe20"5 *

T102

MnO

P2°£S CaO^

MgO

Na20

K26

Ignition

loss

A

NBS

24.3

24.2

1.9

1.0

.18

.27

10.5

7-1

.87

4.2

Rapid

24.6

24.3

1.7

 90

 17

 25

10.4

7.0

, -77

4.1

26.0

100.2

'24.7

24.2

1.9

.97

.lo

.27

10.5

7-0

.81

4.2

26.0

100.7

B

NBS

36 9

36.4

2.8

1.5

.27

.81

1.2

.04

5.4

.24

Rapid

36.9

36.6

2.8

1.3-

.27

-78

1.3

.02

5-2

.23

14.6

100.0

36.5

36.8

2.8

1.3

.27

1.4

.00

5.4

.28

14.6

100.1

c

NBS

35.5

25-4

10.0

.92

.16

.40

3.8

2.5

1.2

6.2

Rapid

36.2

25.0

10.1

.88

.18

.41

3-9

2.3

1.1

6.2

14.1

ioo.4

35.5

24.6

9.9

.85

47

.42 3.7

2.5

1.2

6.3

14.1

99-2

SiOo

AloQ~*

' Fep03*

Ti&2

MnO

P205

CaO

MgO

Na20

K20

Ignition

loss

D

NBS

71.2

9.2 j.2.0

.02

.25

.49

5.1

.19

Rapid

70.8

9.3

12.0

.06

.02

.50

.87

.50

5.0

.21

. 1.1

100.0

71.5

9-6

12.0

.04

.02

.28

.96

.51

5.0

.25

1.1

101.0 '

E

NBS

46.4

12.7

15.8

.03

2.4

6.8

2.7

7.0

.28

Rapid

46.7

12.3

15. 7 _

.06

.03

2.4

6.9

2.5

6.9

.30

6.0

99.8

46.4

12.8

15-6

.06

.03

2.5

6.9

' 2.5

7.0

.31

6.0

100.1

F

NBS

45.0

12.1

8.0

.01

2,0

8.8

4.4

1.6

8.3

Rapid

44.8

11.8

7.9,

.04

.02

2.0

8.8

4.3

1.5

8.4

9.7

99O

45.3

12.4

8.0

 03

.02

2.0

9.0

4.3

1.6

8.4

9.7

100.8

SiOp 

A12&3 

PepO^*

Ti02

MnO

P205

CaO

MgO

Na20

K20

Ignition

loss

G

NBS 

37-6 

10.1 

4.0

.01

.00

 99

12.8

8.1

1.4

7-0

Rapid

37.4 

10.3 

4.1

.02

.01

1.0

13.0

8.0

1.3

7.0

18.4

100.5

36.8 

10.2 

4.0

.01

.01

 96

13.0

8.2

1.4

7-0

18.4

100.0

H

NBS Rapid

45.6 

12.7 

6.4

.06

 _

1.5

14.6

.' 91

6.5

.46

45.5 

13-0 

6.6

.09

.03

1.5

14.6

1.1

6.4

.51

11.7

100.5

45.9 

13-2 

6.2

.09

.03

1.6

14.8

1.0

6.5

.54

11.7

101.4

I

NBS

79.6 

12.8 

1.0

.72

.00

.04

.10

.36

.14

1.6

Rapid

79.0 

12.7 

1.0

 75

.01

.05

.lo

.34

i9

1.6

4.2

100.0

78.9

12.4 

.96

.80

 

.06

.23

 35

.20

1.6

4.2

99.7

S102

A1203

Pe203*

T102

MnO

P205

CaO

MgO

Na20

K20

Ignition

loss

J

NBS

76.5

13.8

1.4

.80

.00

.05

1.2

.46

 17

1.7

Rapid

76.4

13-3

.80

.01

.04

1.5

 51

.19

1.7

4.2

99-7

76.0

13-3

i«3

.85

_ _

.06

1.3

 50

.21

1.8

4.2 yy.4

K

NBS

68.4

20.4

.82

1-3.

.00

.05

1.2

.24

.09

.42

Rapid

69.2

20.2

.78

1-3

.01

.04

1.2

.27

.10

.45

7.1

100. b

69.0

20.8

.82

1.3

.06

1.2

.26

.12

.45

7.1

100.9

L

NBS

63.9

22.3

1.1

 72

.00

.11

.28

 39

5.g

Rapid

64.7

22.0

.95

.72

.01

.11

 32

.46

5-S

1.8

4.3

100. b

64.2

22.0

.98

 79

.12

.40

.44

5.4

1.8

4.3

10O.2

* Total iron as
the National Bureau of Standards standard samples 

used to make up the mixed samples.

Table 3 shows the results obtained by two rapid 

analyses (made at different times) of the National 

Bureau of Standards mixture samples, compared with 

values computed from the analyses reported on the 

original samples by the National Bureau of Standards. 

A single loss on ignition determination was made for 

each mixture sample and the single value for each

sample was used in computing the sum for both rapid 

analyses. FeO values were not reported by the 

National Bureau of Standards and consequently were 

not determined or shown in the table.

The concentration ranges of the tjjixture samples 

and the maximum and average absolute deviations 

based on the 24 values obtained for each constituent 

are shown in table 4.

Table 4. Concentration ranges covered and deviations £or National Bureau of

Standards (N.B.S.) mixture samples.

Constituent

Si02

A1205

Total Fe, as 

Pe2°3

Ti02

MnO

P2°5

CaO

MgO

Na20

K20

Range

24-80

9-36

.8-16

.01-1.5

.00-. 27

.04-2.4

.10-15

.04-8.1

.09-7.0

.19-8.3

Maximum 

deviation

+ 0.8

- .8

- .2

- .2

+ .02

+ .1

+ .2

- .2

- .1

+ .2

Average 

absolute deviation

0.38

 30

.08

.05

.03

.10

.07

.07

.05

SUGGESTED SCHEDULE FOR RAPID ANALYSIS 

OF EIGHT SILICATE ROCK SAMPLES

1st day:

p. m.

3:00- 3:20. Weigh 0. 1000 g samples for 

solutions A.

3:20- 3:30. Fuse samples for solutions A 

with NaOH.

3:30- 3:50. Weigh 1.000 g samplesfor 

solutions B.

3:50- 4:00. Add HF and H2SO4 to crucibles 

containing samples for preparation of solutions B. Place 

on steambath.

4:00- 4:15. Add water to crucibles containing 

samples for preparation of 

solutions A.

2d day:

a, m.

7:45- 7:50. Remove covers from crucibles 

on steambath, solutions B.

7:50- 8:50. Prepare solutions A.

2d day--Continued.

. a. m. 

8:50-10:00, Make solutions and develop the

the color for SiO£, solutions A.

10:00-10:15. Transfer crucibles from the

steambath to a heater and heat 

-until iumes of 803 evolve. 

Solutions B.

10:15-11:00. Take aliquots of Solutions A and 

develop color for

11:00-11:15. Make readings with spectrophotometer for SiO£.

11:15-11:30. Add water to platinum crucibles. 

Place on steambath and allow 

to digest, solutions B.

11:30-12:00. Lunch.

p. m.

12:00-12:05. Remove crucibles from steambath, 

solutions B.

12:05-12:30. Make readings on spectrophotometer for

12:30- 1:00. Prepare solutions B.

16
2d day Continued

p. m.

1:00- 1:15. Withdraw aliquots of solutions B 

for alkalies.

1:15- 1:30. Withdraw aliquots of solutions B

for MnO. Add reagents. Place 

on hotplate.

1:30- 1:55. Withdraw aliquots of solutions B

for TiO2- Add reagents. Make 

readings on spectrophotometer.

1:55- 2.00. Transfer beakers,and solutions 

for MnO to cooling bath.

2:00- 2:30. Withdraw aliquots of solutions B

for P2C>5. Add reagents. Make 

readings on spectrophotometer.

2:30- 2:40. Transfer solutions for MnO from 

beakers to volumetric flasks.

2:40- 3:10. Withdraw aliquots of solutions B 

for total iron. Add to HC1. 

Make readings on spectrophotometer.

3:10- 3:30. Make spectrophotometer readings 

for MnO.

3d day Continued 

a.m.

3:30- 4:15. Calculates^, A^Og, TiO2, 

;, total iron, MnO.

3d day:

a.m.

:45- 8:15. Weigh samples for ignition loss.

8:15- 8:25. Preheat crucibles containing 

samples for ignition loss.

8:25- 8:30. Transfer crucibles containing

samples for ignition loss to the 

muffle furnace.

8:30-9:15. Take aliquots of solutions B for 

CaO and MgO and separate

9:15- 9:55. Titrate CaO.

9:55-10:05. Remove crucibles from muffle and 

transfer to desiccators.

10:05-10:45. Titrate MgO.

10:45-11:00. Weigh crucibles for determination 

of ignition loss.

. 11:30-12:00.

p. m. 

12:00-12:05.

12:05-12:15. 

12:15-12:20.

12:20-12:40. 

12:40- 1:40.

1:40- 2:00. 

2:00- 2:45. 

2:45- 3:30. 

3:30- 4:15.

Weigh samples for FeO. 

Lunch

Add reagents to crucibles for FeO.

Boil solutions for decomposition 

of samples for FeO.

Transfer crucibles containing 

solutions for FeO to beakers.

Titrate FeO.

Transfer solutions for alkalies to 

200 ml volumetric flasks and 

separate RpOo, solutions B.

Mix sample and internal standard 

solutions.

Determine K2O with the flame 

photometer.

Determine Na2O with the flame 

photometer.

Calculate ignition loss, MgO, 

CaO, FeO, K2O and Na2O.

REFERENCES CITED

Betz, J. B., and Noll, C. A., 1950, Total-hardness 

determination by direct colorimetric titration: 

Am. Water Works Assoc. Jour., vol. 42, pp. 49-56.

Brannock, W. W., and Berthold, S. M., The determination of sodium and potassium in silicate rocks 

by flame photometer: U. S. Geological Survey 

Bull, (in preparation).

Bunting, W. E., 1944, The determination of soluble 

silica in very low concentration: Ind. and Eng. 

Chem., Anal. Ed., vol. 16, pp. 612-615.

Davenport, W. H., Jr., 1949, The determination of 

aluminum in the presence of iron: Anal. Chem., 

vol. 21, pp. 710-711.

Kitson, R. E., and Mellon, M. G., 1944, Colorimetric determination of phosphorus as molybdivanodophosphoric acid: Ind. and Eng. Chem., 

Anal. Ed. vol. 16, 379-383.

Pinsl, H., 1944, Photometrische Eisen-Bestimmung 

in Eisen-Erzen und Schlacken mit lichtelektrischer 

Messung: Z. Ver. deut, Chem., Beih, no. 48, 

64-69.

17 INT.-OOP. SEC., WASH., B.C. 11779