Determination of Organic Sulfur With Special Reference to Sulfones and Sulfoxides G. H. YOUSG, 3Iellon Institute of Industrial Research, Pittsburgh, Pa.
A
Procedure
N O S G the several available methods for deterinining
organically combined sulfur, insufficient attention has been paid to that originally described by Brunck ( 1 ) and applied by him to the analysis of sulfur in coals. 55’hile the usual methods offer no difficulty with many sulfur compounds, compounds containing sulfoxide and sulfone linkages occasionally give inconsistent results. A number of investigators have pointed out the stability of sulfonic acids towards pyrolysis; the Carius method for sulfur has been shown to give uniformly low results on compounds when a sulfonic acid is an intermediate product of decomposition (1,2,4). The conventional Parr technique inrolving combustion in a suitable bomb with sodium peroxide ( 3 ) can he made to yield consistent values, but is sensitive to minor variations in manipulation. In addition, tlie relatively expensix e apparatus required is not always available in eyery laboratory. I n working with a series of substituted sulfonanilides the writer found pronounced difficulty in obtaining satisfactory decomposition. Use of the familiar method of Eschka gave consistently low results, as did attempted fusion with sodium carbonate-potassium nitrate mixtures. Combustion in a Parr bomb gave results which were generally satisfactory but were occasionally quite high. The method of Brunck, involving a catalytic oxidation of the sulfur-containing compound v i t h a stream of oxygen in the presence of sodium carbonate and cobalt oxide, gave satisfactory values and could be carried out with greater ease than any of the previous methods tried. The sulfur is quantitatively burned to sulfate and may ultimately be determined b y precipitation and weighing as barium sulfate. The method possesses the distinct advantage of requiring no apparatus not easily obtained or constructed in the laboratory, and no exacting manipulative technique is involved.
Approximately 0.5 gram of sample is accurately weighed into a suitable glass mortar; 2 grams of a 1 to 1 mixt,ui,eof c. P. sodium carbonate and cobalt oxide are added, and the whole is ground together. (The writer has found it advisable to weigh the combustion mixture accurately, as a small correction for possible sulfur in the cobalt oxide may be necessary; this is obtained by running a blank determination, using benzoic acid or other suitable sulfur-free compound as the combustive material.) The sample and combustion mix are transferred to a suitable steel combustion boat by means of a camel’s-hair brush, and covered ivitli a layer of anhydrous sodium carbonate (see Figure 1). Having introduced the charged combustion boat into the tube and assembled the apparatus, a gentle stream of oxygen is turned on, and the medium flame of a Bunsen burner is played beneath the end of the boat away from the oxygen inlet. Within 2 minutes the sample begins to glow; at this point the flame is removed, and the progress of the combustion is regulated by the rate of oxygen flow. After 5 minutes the glow will have traveled the length of tlie boat and the combustion is complete. Occasionally the charge actually ignites; this does no harm, though considerable carbon niay be deposited in the outlet tube. TABLE I. ANALYSESOF TYPICAL SULFOXANILIDES Compound p-Toluenesulion-S-anilide n-Propyl Isopropyl S-Butvl p-Toluenesulfon-m-toluide A--Methyl Ethyl n-Propyl Isoamyl p-Toluenesulfon-p-toluide ‘Y-Isopropyl Isobutyl n-Amyl Isoamyl p-Toluenesulf on-o-toluide N-methyl n-Propyl Isopropyl n-Butyl Isobutyl n-.lmyl Isoamyl
Apparatus Details of the relatively simple apparatus required are shown in Figure 1. A 30-cm. (12-inch) length of Pyrex tube, of approximately 2.5-cm. (I-inch) diameter, is fitted with a groundglass joint at one end; the outlet tube is so arranged as to permit conducting the combustion gases beneath the liquid level in a 600-ml. beaker which contains approximately 300 ml. of 2 per cent sodium carbonate in distilled water. The other end of the combustion tube is connected directly to a suitable mercury valve which acts as a bubble counter; the inlet tube of this valve is connected to the control valve of an oxygen tank. The combustion tube is so arranged that the flame of a Bunsen burner may be played under the far end of the combustion boat, as shown in Figure 1.
\ O 2
Formula
Calcd.
Sulfur Found
70
70
CiaHioOiSS CisHioO2NS CI:H~O~NS
11.07
10.98 11.09 10.44
CisHi:OZSS Ci6Hio02SS Ci;HziO?SS CisHzsOzSS
11.64 11.07 10.56 9.55
11.61 11.08 10.71
CiiH2102SS C:~Hw0zhS CiIH2EOzSS CipHiaOzKS
10.56
10.76 10.04 9.70 9.43
11.64 10.56 10.56 10.09 10.09 9.55 9.55
11.31 10.69
~~
11.Oi 10.56
10.09 9.55 9.55
9.61
10.61 9.82 9.95 9.49
9.70
After cooling, the oxygen stream is turned off, and the combustion boat and contents are introduced direct into the 600-ml. beaker. The charge is dissolved with the aid of a stirring rod and the boat removed after rinsing. The contents of the beaker are carefully acidified with hydrochloric acid, a few milliliters of bromine water are added, the solution is heated t o boiling, the bromine is driven off, and the solution is filtered. The sulfate is precipitated from the hot filtrate with barium chloride in the usual manner. Data showing the analyses for 18 typical sulfonanilides are summarized in Table I.
!,,II It J
Literature Cited
T-
(1) Rrunck, O., 2. angew. Chem., 18,1560 (1905). (2) Gabriel, S., Ber., 22, 1154 (1889). (3) Parr, S. W., Wheeler, W. F., and Berolaheimer, R., J. IND.
[email protected].,1, 689 (1909). (4) Voss, ‘A’., and Blanke, E., Ann., 485,281 (1931).
FICCRE1.
DET.4ILS
OF
RECEIVEDAugust 13, 1938. Contribution Stoner-XIudge. Inc., Industrial Fellowship a t stitute. This work was carried out while the in residence a t t h e School of Chemistry and The Pennsylvania State College.
APPARATUS 686
from t h e Mellon Inauthor wV&5 Physics of
