The Determination of 

Sulfate and Sulfide Sulfur 

in Rocks or Minerals

By ANGELINA C. VLISIDIS

CONTRIBUTIONS TO GEOCHEMISTRY

GEOLOGICAL SURVEY BULLETIN 1214-D

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1966
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

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

Washington, D.C. 20402 - Price 15 cents (paper cover)
CONTENTS

Page

Abstract_____--__-___-_______-__---____,__-_-__-_---_-_______-_- Dl

Introduction. ______________________________________________________ 1

Preparations. _________._.-.__-_-.__.._-_---__----.________._.._____ 2

Standard samples____________________________________________ 2

Reagents. _______________.-_-___-____-__-_-__-_-___-_______-_- 2

Procedure._______________________________________________________ 2

Results__ __________-______-_____----__--_--_----_-_-_-___-___--_ 3

References.._ _____________________________________________________ 5

TABLE

Page 

TABLE 1. Results of sulfide and sulfate sulfur analyses in which varying

amounts of a sulfate standard were added to sulfide minerals.. _ D4

m

209-517 66

CONTRIBUTIONS TO GEOCHEMISTRY

THE DETERMINATION OF SULFATE AND SULFIDE 

SULFUR IN ROCKS OR MINERALS

By ANGELINA C. VLISEDIS

, ABSTRACT

A method for the determination of sulfate and sulfide sulfur that occur 

together in rocks or minerals is presented. All the sulfate sulfur is converted 

to barium sulfate in an inert atmosphere to prevent oxidation of any sulfide 

sulfur. Cadmium chloride is added to precipitate any sulfide ion that may be 

liberated. The sulfate sulfur is then measured indirectly by the determination 

of the barium and is therefore unaffected by any. subsequent oxidation of the 

sulfide sulfur. Total sulfur is determined on a separate sample, and sulfide 

sulfur is calculated by difference.

INTRODUCTION

A procedure is needed whereby insoluble sulf ates and insoluble sulfides in a rock or mineral can be determined. A rock that contains 

sphalerite, pyrite, barite, and gypsum cannot readily be analyzed for 

sulfide and sulfate by any published method.

Approaches designed to isolate sulfide sulfur followed by the determination of the sulfate sulfur were tried and found wanting. For 

example, attack with tin and hydrochloric acid (Treadwell and Hall, 

1919, p. 368-372) failed to dissolve insoluble sulfides in minerals such 

as chalcocite, bornite, and chalcopyrite. Tin and hydrobromic acid 

(Harding, 1881) or hydriodic and hydrochloric acids and mercury 

(Murthy and others, 1956, 1960), while effective in dissolving sulfide 

.minerals, gave low results for sulfate sulfur, possibly because of partial 

reduction of sulfate ion.

Separation of the sulfate from the sulfide by selective solution of 

the sulfate in ammoniacal or sodium hydroxide solution of versene 

(Pfibil and Maricova, 1952; Belcher and others, 1954; Morris, 1959) 

failed to dissolve barite completely. Prolonged boiling with a sodium 

carbonate-versene solution did dissolve the barite but also attacked 

some of the sulfide minerals.

Dl
D2 CONTRIBUTIONS TO GEOCHEMISTRY

In the method presented in this paper, sulfate sulfur is converted to 

barium sulf ate by digesting the sample with an acidified solution of 

barium chloride in an inert atmosphere to prevent oxidation of any 

sulfide sulfur. Any insoluble sulf ate present remains with the precipitated barium sulfate. Cadmium chloride is added to precipitate any 

sulfide ion that may be liberated in the digestion. This addition 

insures that no sulfide sulfur is oxidized in the initial filtration. The 

sulfate sulfur is then measured indirectly by the determination of 

barium in the barium sulfate precipitate and is, therefore, unaffected 

by any subsequent oxidation of the sulfide sulfur. Total sulfur is 

determined on a separate sample, and sulfide sulfur is calculated 

by difference.

PREPARATIONS

STANDARD SAMPLES

No analyzed standard samples containing both sulfate and sulfide were available for direct evaluation of this method. A sulfate standard was prepared of 

gypsum and barite (each ground to pass a 100-rnesh sieve) mixed in the ratio 

3:1. This was carefully analyzed for sulfate content.

Twelve of the more common sulfide minerals were also prepared as standards. 

After grinding to pass 100-mesh sieve each was treated with 1 percent hydrochloric acid at room temperature for 30 minutes, filtered, and washed with water 

to remove any sulfate that may have been present due to oxidation. Each 

sample was then dried with acetone, and placed in an airtight bottle. These 

samples were then analyzed for total sulfur, the values for which are given in 

the table as S03 .

REAGENTS

Cadmium chloride_________ 10 percent w/v aqueous solution. 

Barium chloride___________ 10 percent w/v aqueous solution. 

Hydrochloric acid_,_;______ 1 percent v/v aqueous solution. 

Ammonium chloride__________ 2 percent w/v aqueous solution. 

Sodium carbonate___________ 2 percent w/v aqueous solution.

PROCEDURE

Determination of sulfate sulfur

1. Transfer an accurately weighed 0.5000-gram sample to a 300-ml Erlenmeyer 

flask fitted with a two-hole stopper with a glass tube extending down into 

the flask.

2. Add 10 ml of Cd012 solution, 10 ml of BaCl2 solution, and 200 ml of water and 

sweep out with nitrogen gas for 15 minutes.

3. Add 2 ml of cone HC1 and heat the solution for one-half hour at about 50°C, 

continuing to bubble nitrogen through it. Remove from the heat, stopper, 

and let stand overnight.
133

4. Filter the solution through an 11-centimeter Whatman No, 42 paper; wash 

the residue 10 times with NEUC1 solution to remove all the excess barium 

reagent (very important). Discard the filtrate.

5. Transfer the residue and paper to a platinum crucible and ignite. Cool.

6. Add 5 g of Na2CO3 and fuse.

7. Put the crucible into a 400-ml beaker, add about 200 ml of water, and digest 

on the steam bath until the cake is completely broken up.

8. Remove the crucible from the beaker, wash with water, dissolve any adherent 

material with 1+1 HC1 and rewash. Add methyl-red indicator to the 

beaker and continue acidification of the solution with the HOI; add an 

excess of acid so that all the salts except the insoluble sulfates go into 

solution.

9. Adjust the acidity of the solution to the proper concentration for the precipitation of BaS04 by first adding NH4OH until the solution is just yellow 

avoid an excess of ammonia and then add 1+1 HC1 drop by drop until 

the solution reverts to pink. Finally, add 3 ml of 1+1 HC1 and dilute the 

solution to 300 ml.

10. Add 0.5 g of Na2SC>4, digest for 2 hours on the steam bath with occasional 

stirring, and let stand overnight.

11. Filter the solution, using a No. 42 paper, and wash the residue thoroughly 

10 times with water to remove all the excess sulfate.

12. Transfer the residue and paper to a platinum crucible, burn off the paper, 

fuse with 5 g of Na2C03 , and leach with water until the melt is completely 

broken up.

13. Filter, wash the precipitate and paper with Na2C03 solution, and dilute to 

300 ml. Add two drops of methyl-red indicator and 1+1 Hd dropwise 

until the solution becomes pink; then add 3 ml of 1+1 HC1 in excess.

14. Add 10 ml of BaCL solution slowly while stirring, digest the solution on the 

steam bath for 2 hours, and let stand overnight.

15. Filter on No. 42 paper and wash 10 tim.es with water.

16. Burn off the paper in a weighed platinum crucible at a temperature below 

red heat. When all the carbon has been burned off, add one drop of 1+1 

HsSO-t and a few milliliters of HF to the crucible. Evaporate the liquid 

on the steam bath, drive off the H:! SC>4 carefully, and ignite at 900°C in a 

muffle furnace for half an hour. Cool in a dessicator, weigh as BaSO-4, and 

compute the SOs in the sample.

Determination of total sulfur

Determine total sulfur by any suitable method.

Calculation of sulfl.de sulfur

Subtract the value for sulfate sulfur from total sulfur to obtain the value for 

sulfide sulfur.

RESULTS

Table 1 lists the results of the analyses in which 0 to 0.1088 g of SO3 

from the sulfate standard was added to 0.2000-g samples of each of 

the 12 sulfide minerals.
»D4

-TABLE 1. 'Results of sulfide and sulfate sulfur analyses in which varying amounts 

r ' ' . - of a sulfate standard were added to sulfide minerals , ;

Sulfide mineral

Bornite (0.2000 goO.1271 g 80s): 

Totalsulfur _ ' _________ ' _ . . _

Sulfate found _______________ .- _

Sulflde calculated. __ ... _ __ . __ ...; ...

Chalcocite (0.2000 goO.1051 g 80s): 

Totalsulfur ___ .. ___ . ___ ............

Sulfate found.. __________________

Sulfide calculated- _____________

Chalcopyrite (0.2000 goO.1673 g SOa): 

Totalsulfur _________ . _________

Sulfate found __________________

Sulfide calculated ___________ ..

Cobaltite (0.2000 goO.0883 g SOa): 

Totalsulfur _____________ _ . ..

Sulfate found ____________ . ....

Sulflde calculated __________ .....

CovelUte (0.2000 goO.1587 g S03): 

Totalsulfur. ____ ________

Sulfate found _________________

Sulfide calculated- ______________ .

Marcasite (0.2000 goO.2565 g SOa): 

Totalsulfur- ______________ __ .

Sulfate found _____________ . __ .

Sulfide calculated.. ______ ... ....

Pyrite (0.2000 goO.2615 g S03): 

Totalsulfur ________ ...

Sulfate found. _________________ .

Sulfide calculated ______ _ ...

Pyrrhotite (0.2000 goO.1842 g S03): 

Totalsulfur _______ _ ... ....

Sulfate found ____________ ....

Sulfide calculated _____________

Sphalerite (0.2000 goO.1632 g SOa): 

Total sulfur.. ____ . __ . ______ . __ . .

Sulfate found __________________

Sulflde calculated ..........................

Arsenopyrite (0.2000 goO.0140 g SOa): 

Totalsulfur-. __________________ .-.

Sulfate found. ______ . . __ ....

Sulfide calculated _______________

Galena (0.2000 goO.0664 g SO3): 

Totalsulfur ___________________

Sulfate found...: ________________

Sulflde calculated ______________ ..

Stlbnite (0.2000 goO.1318 g SOa): 

Totalsulfur. ....................................

Sulfate found ___________________

Sulflde calculated _______________

Results of analyses in which -were added indicated 

amounts of standard sulfate mixture, all amounts 

- in grains of 80s . ,;

0.0000

0.1271 

.0000

. 1271

0.1051 

.0000

.1051

0. 1673 

.0003

.1670

0.0883 

.0001

.0882

0. 1587 

.0003

.1584

0. 2565 

.0001

.2564

0.2615 

.0000

.2615

0. 1842 

.0002

.1840

0. 1632 

. . 0005

.1627

0.0140 

.0001

.0139

0.0664 

.0002

.0662

0. 1318 

.0021

.1297

0.0022

0.1291 

 . 0022

.1269

0.1071 

.0022

.1049

0. 1696 

.0024

.1672

0.0902 

.0021

.0881

0. 1606 

.0023

.1583

0. 2584 

.0024

.2560

0. 2633 

.0024

.2609

0. 1862 

.0023

.1839

0. 1649 

.0024

.1625

0. 0156 

.0034

.0122

0.0693 

.0027

.0669

0. 1345 

.0023

.1322

0. 0218

0.1'482 

.0211

.1271

0,1268 

.0218

.1050

0. 1893 

.0214

.1679

0. 1099 

.0212

.0887

0. 1803 

.0215

.1588

0. 2779 

.0213

.2566

0.2827 

.0217

.2610

0. 2050 

.0213

.1837

0. 1860 

.0221

.1639

0. 0351 

.0213

.0138

0. 0884 

.0210

.0674

0. 1540 

.0208

.1332

0. 0435

 6. 1700 

.. ..0430

. 1270

0. 1481 

.0429

.1052

0. 2107 

.0434

.1673

0. 1318 

.0440

.0883

0. 2025 

.0442

.1583

0. 3010 

.0438

.2572

0. 3055 

.0439

.2616

0.2270 

.0434

.1836

0. 2064 

.0428

.1636

0. 0569 

.0405

.0164

0. 1103 

.0466

.0637

0. 1744 

.0400

.1344

0.1088

. 0. 2355 

. 1087

.1268

0.2136 

.1079

.1057

0.2758 

.1085

.1673

0.1967 

.1080

.0887

0. 2677 

.1094

.1583

0. 3648 

.1081

.2567

0. 3694 

.1076

.2618

0. 2921 

.1080

.1841

0. 2713 

.1074

.1639

0.1231 

.1058

.0173

0.1746 

.1072

.0674

0. 2411 

.1084

.1327
DETERMINATION OF SULFATE AND SULFIDE SULFUR D5

Recoveries obtained were very satisfactory, although when arsenopyrite, galena, or stibnite was present the results were not as good as 

those obtained when any of the other nine sulfides were used. In 

samples where elemental sulfur is present, preliminary treatment with 

carbon disulfide to remove sulfur would be required. Any organically combined sulfur, of course, would be included in the total sulfur, 

and the sulfide sulfur would be in error. Sulfate-containing silicates, 

such as hauynite and noselite, and sulfide-containing silicates such as 

lazurite, helvite, and danalite are soluble in hydrochloric acid and 

present no problems.

REFERENCES

Belcher, R., Gibbons, D., and West, T. S., 1954, The evaluation of barium sulfate 

precipitates by a titrimetric method: Chemistry and Industry, Jan. 30, 1954, 

p. 127-128.

Harding, A., 1881, Ueber die Darstellung und Anwendung der Bromwiisserstoffsaure in Laboratorien: Deutsche chem. Gesell. Ber., v. 14, p. 2085-2092.

Morris, A. G. C., 1959, Dissolution of barium sulfate by EDTA and sodium hydroxide : Chemist-Analyst, v. 48, p. 76.

Murthy, A. R. Vasudeva, Narayan, V. A., and Rao, M. R., 1956, Determination 

of sulfide sulfur in minerals: Analyst, v. 81, p. 373-375.

Murthy, A. R. Vasudeva, and Sharada, K., 1960, Determination of sulfide sulfur 

in minerals: Analyst, v. 85, p. 299-300.

Pribil, Rudolf, and Maricova, Drahomira, 1952, Gravimetric determination of 

barium and sulfates: Chem. Listy, v. 46, p. 542-544.

Treadwell, F. P., and Hall, W. T., 1919, Analytical chemistry [5th ed.]: New 

York, John Wiley & Sons, v. 2, 940 p.

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