Determination of Forms of Sulfur in Insoluble Residues from Hydrogenated Coal R. F. ABERNETHY, H. &I. COOPER, AND E. C. TARPLEY Central Experimental Station, Bureau of Rlines, Pittsburgh, Pa.
T
HE purpose of this paper is to describe a procedure for determining the forms of sulfur in insoluble residues obtained from hydrogenation of coal, and to give a trend of behavior of sulfur during hydrogenation. For many years sulfur has played an important role in the use of coal (S), b u t in the present-day industrial use it is more important than ever to know not only the sulfur content but also its various forms and distribution. Powell and Parr ( 7 ) developed a procedure for Illinois coal and showed that the principal forms of sulfur are sulfate, pyritic, and organic. Later Powell (5) analyzed representative coals of the United States. This scheme of analysis was used in analyzing the insoluble residues from hydrogenated coal. These residues were obtained from Fisher and Eisner (b), part of whose work has covered Pittsburgh bed coal from the Bureau of Nines Experimental Mine, Bruceton, P a . Their charge for hydrogenation was 100 grams of coal, 100 grams of tetrahydronaphthalene, and 1 gram of stannous sulfide. The initial hydrogen pressure was 703,100 kg. per sq. meter (1000 pounds per square inch) with varying time and temperature. TABLEI. FoRhis O F SULFURI N Residue
Ash
Sulfide Sulfur
%
%"
12.7 27.3 30.0 52.8
0.57 1.51 1.73 3.76
%
ISBOLCBLE
RESIDUES
Sulfate Pyritic Organic Total Sulfur Sulfur Sulfur Sulfur Calcd. Detd.
%
%
%
%
0.16 0 . 7 0 1.95 0.14 0.63 3.19 0.18 0.60 3.56 4 0.18 0.39 6 . 4 . 6 Coalb 6.4 0.06 0.84 0.72C .. Corrected for sulfur in 1 gram of catalyst (SnS added). b Original coal, moisture-free basis. c Calculated by subtracting sum of sulfate and pyritic from total 1 2 3
..
0.95 2.30 2.60 5.30
..
0.14 0.12 0.18 0.61
% 1.91 3.23 3.56 8.. 4 0
..
sulfur.
The analyses showed small amounts of sulfate and pyritic sulfur, which indicated that the greater portion of the sulfur was apparently in the organic form. However, on the initial extraction with dilute hydrochloric acid, hydrogen sulfide was evolved. Later, quantitative determinations showed that most of sulfur was present as hydrochloric acid-soluble sulfides and that the organic sulfur, as determined by the standard method, was erroneously high. A procedure was then formulated by combining Powell's method for forms of sulfur in coal (5) with his method for forms of sulfur in coke (6) t o determine directly sulfide, sulfate, pyritic, and organic sulfur.
with cold water. The residue was saved for the pyritic sulfur determination. To the filtrate in a 2.50-cc. beaker 20 cc. of saturated bromine water were added. The filtrate was heated to boiling, and while hot was made alkaline with dilute ammonium hydroxide (1 part of concentrated ammonium hydroxide to 1 part of water) ; the precipitate containing the iron was filtered off and washed. The filtrate was neutralized with concentrated hydrochloric acid and 1 cc. excess added and heated to boiling, 10 cc. of hot barium chloride (10 per cent) being added. The barium sulfate was allowed to settle overnight, filtered on an ashless filter paper, ignited a t 900 ' C., and weighed. PYRITIC SULFUR. The residue on the filter paper from the sulfate determination above was placed in a 250-cc. beaker, the filter paper was shredded with a stirring rod, and 100 cc. of dilute nitric acid (1 part of nitric acid, specific gravity 1.42, to 3 parts of water) were added and allowed to digest, with occasional stirring, a t room temperature for 24 hours. The contents were placed on a filter and washed six times with cold water. The residue was saved for the organic sulfur determination. To the filtrate 5 cc. of dilute hydrochloric acid ( 2 parts of concentrated hydrochloric acid t o 1 part of water) were added and evaporated to dryness on the steam bath. This residue was dissolved in 5 cc. of concentrated hydrochloric acid and diluted with 30 cc. of water. The iron was precipitated with dilute ammonium hydroxide and removed by filtration. The sulfur in the filtrate was determined as under sulfate sulfur above. ORGANIC SULFUR. The residue from the pyritic sulfur determination was dried and the filter paper shredded; it was intimately mixed with 5 grams of Eschka mixture and covered with 5 grams more of Eschka mixture in a 30-cc. porcelain crucible. The crucible was placed in a cold electric muffle, heated to a dull-red heat for 15 minutes, and cooled. The contents mere mixed well in the crucible, covered with 2 grams of Eschka mixture, and again heated in an electric muffle to 800" C. for 1.5 hours. After cooling, the contents of the crucible were washed into a 250-cc. beaker, 10 cc. of saturated bromine water were added and made acid with concentrated hydrochloric acid and filtered, and the residue was washed with hot water. The sulfur in the filtrate was determined as under sulfate sulfur above. Blanks were run on reagents used. TOTAL SULFUR. The total sulfur was determined by the standard Eschka method ( I ) , Table I gives the results, on the percentage basis, obtained when the modification of the standard sulfur forms method is applied to the insoluble residues. Residues 1 , 2 , 3 ,and 4 represent increasing degrees of liquefaction of the coal as shown by the ash content ( 2 ) . The accuracy of the procedure is shown by comparing the calculated total sulfur with the determined total sulfur. The calculated total sulfur is the sum of the sulfide, sulfate, pyritic, and organic sulfur. It is evident that unless the sulfide sulfur is determined, the organic sulfur will be erroneously high.
Procedure SULFIDESULFUR(EVOLUTION METHOD, 4). The 60-mesh residue (0.500 gram) was placed in a 300-cc. Erlenmeyer flask fitted with a two-hole rubber stop er. A separatory funnel was inserted in one hole, and in the otter, a glass delivery tube leading to the bottom of a 300-cc. tall-form beaker, containing 30 cc. of ammoniacal cadmium chloride (30 grams of CdCl, in 300 cc. of water added to 800 cc. of water and 1200 cc. of ammonuim hydroxide) and 200 cc. of distilled water. To the flask containing the residue, 60 cc. of dilute hydrochloric acid (1 part of acid and 1 part of water) were added slowly to permit even bubbling through the cadmium chloride solution. The flask was heated to boiling, and slowly boiled until all the hydrogen sulfide had been expelled by the steam. The cadmium chloride solution containing the cadmium sulfide was cooled to room temperature in ice water, acidified with 30 cc. of concentrated hydrochloric acid, and titrated with standardized iodine, using starch an an indicator. Blanks were run on the reagents used. SULFATESULFUR. The contents of the flask from the sulfide determinations were washed onto a filter and washed six times
TABLE 11. FORMS OF SULFUR IN INSOLUBLE RESIDUES Residue 1 2 3
4
0
Residue Found
Sulfide Sulfur
Sulfate Pyritic Sulfur Sulfur
Organic Sulfur
Total Sulfur
Grams
Grama
Gram
Gram
Gram
Gram
Gram
55.7
0.32 0.41 0.42 0.52
0.63 0.62 0.63 0.73
0.08 0.03 0.04 0.08
0.09 0.04 0.04
0.39 0.17 0.15 0.05
1.09 0.86 0.86 0.88
26.8 24.3 13.8
0.02
Corrected for sulfur from catalyst (SnS).
Table I1 gives some trends on the behavior of the sulfur during hydrogenation. From the total residue found, the grams of the various forms were calculated. This does not give a complete sulfur balance, because some of the sulfur is in the gases and some in the liquid fraction. The third column in Table I1 gives the sulfide sulfur corrected for the sulfur from 389
INDUSTRIAL A S D ENGINEERING CHEMISTRY
390
the catalyst (SnS), which was added. The amount of sulfide sulfur increases with the time of hydrogenation, while the pyritic and organic decrease. The pyritic sulfur may be high, because it is determined directly from the nitric acid extraction and may contain some of the organic sulfur. Residue 1 (least hydrogenated) has a much higher total sulfur content than residues 2,3, and 4,which have almost the same amount of sulfur; yet residue 4 (13.8 grams) has about the same amount (0.88 gram) as residue 2 (26.8 grams) which has 0.86 gram. The sulfate sulfur is shown to be erratic by the data in Tables? and 11. Since residue 4 had been standing in the laboratory considerably longer than the others and had a higher percentage of sulfate sulfur, it was suspected of having gained a t the expense of the sulfide sulfur. The writers wish to thank C. H. Fisher and Abner Eisner of
VOL. 10, NO. 7
the Organic Laboratory for providing the insoluble residues for this work. Literature Cited (1) Am. SOC.Testing Materials, “Standards on Coal and Coke,” p. 21, 1936. (2) Fisher, C. H., and Eisner, Abner, IND.ENG.CHEM., 29, 1371-6 (1937) (3) Fuel Economist, 13, 495-7 (1937). (4) Griffin, R. C., “Technical Methods of Analysis,” 2nd ed., p. 142, New York, McGraw-Hill Book Co., 1927. (5) Powell, A. R., Bur. Mines Tech. Paper 254 (1921). (6) Powell, A. R., IND.ENG.CHEM., 15, 951-3 (1923). (7) Powell, A. R., and Parr, S. W., Expt. Sta., Univ. Illinois, Bull. 111, 10-35 (1919).
RECEIVED May 3, 1938. Presented before the Division of Gas and Fuel Chemistry a t the 95th Meeting of the American Chemical Society, Dallaa, Text%, April 18 to 22, 1938. Published b y permission of the Director, Bureau of Mines. United States Department of the Interior. (Not subject to copyright.)
Determination of Small Quantities of Methvl Bromide in Air J RUTH L. RUSBEY AND NATHAN L. DRAKE Bureau of Entomology and Plant Quarantine, U. S. Department of Agriculture, College Park, RId.
A method is proposed for the determination of methyl bromide in air of fumigated spaces. The procedure involves saponification of the methyl bromide by alcoholic potassium hydroxide, removal of the alcohol, oxidation of the bromide to bromate by sodium hypochlorite, and iodometric titration of the bromate. Results are reported of analyses of 13 samples ranging from 0.0480 to 0.0065 gram. The average error is -1.7 per cent; the greatest error is -3.5 per cent.
T
HE discovery that methyl bromide is an effective fun& gant for a number of insects and is a t the same time
relatively innocuous to plant tissues has resulted in a good deal of experimental work with this compound by entomologists. Consequently, the need has arisen for a method of determining methyl bromide in the air of fumigated spaces, and it is the purpose of this paper to present such a method. There is little information in the literature bearing directly on the determination of methyl bromide. Kuckolls (5) determined the concentration of alkyl halides, including methyl bromide, in air by condensation with liquid air and subsequent pressure measurements a t the original temperature. Glaser (2) reported determining the methyl bromide content of air in a refrigerator factory by drawing 100 liters of air through sodium methylate solution, then acidifying and titrating with 0.01 X silver nitrate and ammonium thiocyanate. The Dow Chemical Company (1) has proposed a method which involves saponification of the methyl bromide with alcoholic potassium hydroxide solution and subsequent titration with standard silver nitrate solution, using dichlorofluorescein as an adsorption indicator
h number of samples of methyl bromide were analyzed in this laboratory by the Dow method, but with small samples the end point was very unsatisfactory. The procedure to be described is more time-consuming, but the end point is much sharper and easier to detect. Oxidation of the bromide to bromate also introduces a sixfold magnification in the results, which further contributes t o the accuracy. After saponification with alcoholic potassium hydroxide, the bromine of methyl bromide is in the form of potassium bromide. The alcohol can be removed readily and an aqueous solution obtained which contains potassium bromide and excess potassium hydroxide. Leipert and Watzlawek (3) have described a method, based on earlier work by van der hleulen ( d ) , for the microanalytical determination of bromine in organic substances which consists essentially in combustion of the substance in oxygen, absorption of the combustion products in aqueous sodium hydroxide solution, and subsequent oxidation of the bromine to bromate. The oxidation and titration processes were easily adapted to a larger scale for the present purpose. The method of analysis to be described involves passing air containing methyl bromide through heated alcoholic potassium hydroxide solution to produce saponification. The mixture is diluted with water and the alcohol removed by distillation. The bromide is then oxidized to bromate by sodium hypochlorite in slightly acid solution, the excess hypochlorite removed, potassium iodide added, and the iodine titrated with standard sodium thiosulfate solution. Apparatus A special saponification apparatus is required, which is shown in Figure 1. (This is a slight modification of an apparatus described in a private communication from the Dow Chemical Company.) The glass tubing is 6 mm. in diameter except for portion EE, which is capillary tubing of about 1-mm. diameter. The bulbs are 3 cm. in diameter except for the three at the bottom, whose diameter is 2.5 cm. A tin can of suitable dimensions, covered with thin asbestos, is used for the jacket, D, which is held in place by a rubber stopper at F. A piece of cardboard is used
