Microdetermination of Sulfur in Organic Compounds A L STEYERMARK, ESTHER BASS, AND BELLA LITTMAN H o f f m a n n - L a Roche, Inc., N u t l e y , N . J . A micromethod for determining sulfur is presented which employs the Carius combustion followed by titration of the resulting sulfate with barium chloride. The tetrahydroxyquinone indicator method of Ogg, Willits, and Cooper is used.
T
H E use of the tetrahydroxyquinone indicator (prepared by IT.
excellent. results with sulfanilamide, sodium sulfite, and sulfanilic acid, and is now generally used in this laboratory. Table I1 gives the data for a number of analyses performed this way.
H. and L. D. Betz, Philadelphia) in bhe microdetermina-
tion of sulfur in organic compounds has heen described by Hallett and Kuipers ( 2 ) ,Sundberg and Rover (e),.Ilicino ( I ) , and Ogg, Willits, and Cooper (4). All these authors used the catalytic combustion method to destroy organic material and to convert the organically bound sulfur to sulfate, previous to the titration with barium chloride.. A demonstration b l Willits and Ogg in their laboratorj convinced the present authors of the value of the illuminated titration stand technique, and they decided to adopt the method in this laboratorg . Good results were obtained with sulfanilic acid in a Pregl ( 5 ) tube, when either alkali ( 2 , 6 ) or bromine water (4) was used as the absorbent. However, when samples of sulfanilamide were burned either by the above method or in the Grote apparatus ( 6 ) , low results were obtained. The data for these det,erminations are shown in Table I. (Killits states that recently difficulties have been encountered in his laboratory with the catalytic method.) Samples of sulfanilamide were then burned by the Carius method, after which the resulting sulfate was titrated with barium chloride by the illuminated stand technique of Ogg, Willits, and Cooper. This procedure gave
EXPERIMENTAL
Enough sample should be used so t,het 3 to 5 ml. of 0.01 3barium chloride will be needed for the titration. [Ogg, Willits, and Cooper (.$) used 0.02 N barium chloride, while the authors obtained good results with 0.01 N . The barium chloride was standardized with 0.01 N potassium sulfate using the tetrahydroxyquinone indicator.] The sample is placed in a micro-Carius combustion tube along with 15 to 20 mg. of some pure sodium or potassium salt [such as oxalate, acid phthalate, chloride, etc. ( 3 )j and 0.7 ml. of fuming nitric acid, specific gravity 1.49 to 1.50. The Carius tube is sealed and heated for about, 7 or 8 hours a t 250 ’ C. After combust,iori, the tubes are opened, the mixture is quantitatively transferred to a small beaker, and the contents are evaporated to dryness on a steam bath. The residue of sodium or potassium acid sulfate is transferred to a cuvette ( d ) , after which the solution is made alkaline with 0.1 -3- sodium hydroxide, using phenolphthalein as an indicat,or, and back-titrated with 0.01 N hydrochloric acid just to expel the color. From this point, the procedure is identical to that outlined by Ogg, Willits, and Cooper. ACKNOWLEDGMENT
In addition to the work done by the authors of this paper, other analyses shown in t.hese tables were done by Marian Faulkner, Constance O’Hara, Ruth Reed, Margaret Sullivan, and llarie Wal..er, all of whom are in the emploj of this Company.
Table I. Determination of Sulfur in Compounds Using Catalytic Combustion and Ogg, Willits, and Cooper Titration
Compound
Empirical Formula
Sulfanilamide“ CeHsNZOrS
Sulfanilic acid
5
CeHiSOaS.Hz0
LITERATURE CITED
Weight Sa&le, Mg.
4.914 5.049 4.331 4.539 5.021 4,430 3.989 4,472 4.509 4.119 4.022
111. 4.97 5.35 4.53 4.59 4.87 4.88 4.20 4.70 4.75 4.34 4.31
(1) Alicino, J. F., ASAL.CHEM.,20, 85 (1948).
Percentage Sulfur Found Calculated 16.21 18.62 16.99 16.77 16.21 15.55 17.66 16.88 16.84 16.89 16,77 16.89 17.18
(3) (4)
(5)
(0)
U.S.P. reference standard.
RECEIVED November 8. 1947
Table 11. Determination of Sulfur in Compounds Using Carius Combustion and Ogg, Willits, and Cooper Titration Compound Sulfanilamide”
Sodium sulfite Sulfanilic acid Researchb
Empirical Formula CsHaSzOzS
XarSOs
CsIl;NO,S. HoO CmH1;OsXzSNa CioHl-O-N2SNa
CsHiiOzNoS
W.,IND.EKG.CHEM.,d x . 4 ~ED., . 12,360 (1940). Niederl, J. B., and Niederl, V., “Micromethods of Quantitative Organic Analysis,” 2nd ed., p. 182, New York, John Wiley 8: Sons, 1942. Ogg, C. L., Willits, C . O., and Cooper, F. J., 4 1 u . 4 ~ . CHEM.,20, 83 (1948). Roth, H., “Quantitative Organic Micioanalysis of Frits Pregl,” 3rd English ed. tr. by E. B. Daw, p . 95, Figure 129(b),Philadelohia. P. Blakiston’s Son 8: Co.. 1937. Sundberg, 0. E., and Royer, G. L., IKD. ESG.CHEM.,AXAL.ED., 18,719 (1946).
(2) Hallett, L. T., and Kuipers, J.
Telght of o , o l .v Percentage Sample, BaClz, ___ Sulfur M g hI1. Found Calculated 3.44 18.63 18.62 2.960 4.11 18.93 3,480 3.77 18.71 3.230 3.87 18.91 3.280 6 22 18 66 5.346 18.56 2,488 2.88 3.29 18.69 2.822 2.89 18.61 2.489 25.43 4.87 25 50 3.061 1.80 16.81 16.77 1.716 3.29 10.14. 10.09 5.228 2.91 8.91 5,236 9.00 2.76 9.13 4.845 16.17 4.26 15.65 4.364 4.48 15.69 4.576 20.52 5.65 20.32 4.458 6.44 2.96 6.10 7.778 3.35 9.00 9.25 5.803
Identification of Pennsylvania Lubricating Oils-Correction In the article on “Identification of Pennsylvania Lubricating oik,” [Hersh, Fenske, Matson, Koch, Booser, and Braun, ASAL. & E x , 20, 434 (1’&8)] a line was omitted from the text on page 143. The first sentence under the heading “Other Methods” should read: “In addition to the methods of identification described above, more elaborate procedures can be employed which utilize the physical and chemical characteristics of successive or selected fractions of the lubricating oil separated by distillation, solvent extraction, treatment with adsorbents, etc.” I n line 4 of the nest paragraph on page 443 “narrow-out fractions” should read “narrow-cut fractions.” On page 438 under the subhead “Treatment with Adsorbents,” line 11 should read: “1.9-em. (0.75-inch) diameter.”
CiHsONnS CZ~HIZOENZS. 1/zHa0 ClrH1;07NzSNa U.S.P. reference standard. b Purity of research compounds verified by analysis of other elements present. Q
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