V O L U M E 25, NO. 1, J A N U A R Y 1 9 5 3 Table I.
Analysis of Thiophene Solutions Containing 1.85% S
Saniple SO.
1 2
3 4
5
6 7 8 9 10
a
197
HNO,, N 4 8 8 8 8 8 8 8 8 8
BaSOa, Grams 1.20 1.18 1.20 1.13 1.28 1.24 1.25 1 22 L24 1.28
S Found,
%
1.85 1.82 1.85 1.74 1.97 1.91 1.93 1.88 1.91 1.97 1.89 1.84 1.97 1.89 1 86 1.93 1.70 1.97 1 93 1.89
During the course of this investigation it became necessary t o substantiate the fact that organic sulfides would not be oxidized t o sulfate by nitric acid. Accordingly, diphenyl sulfide and diethyl sulfide were each refluxed separately with 12 N nitric acid for 3 hours, after which time no sulfate could be detected in either case. Furthermore, these two sulfides vere each added t o separate samples of solutions of thiophene in cyclohexane (Table 11, samples 21 and 22) and the mivture heated at reflux tempeiature for 3 hours with 8 N nitric acid, hut in neither cme was there observed any additional sulfatc ascribable t o the oxidative decomposition of the added sulfide. ACKNOULEDG\IENTS
The many helpful suggestions of Hazel Tonilirison are gratefully acknowledged. Thanks are due also t o the Socony-Vacuum Oil Co. for its generosity in supplving thiophene and derivatives.
1 gram oxalic acid added. LITERATURE CITED
Table 11. Analysis of Low Sulfur Samples ”Os, Thiophene S Total S SO. N Present, % Found, %
Sample 210
8 22b 8 23 12 24 12 1 grain of diphenyl sulfide added.
0.37 0.36 0.37 0.38 0.18 0.16 0.18 0.17 0 . 5 gram of diethyl sulfide added.
I n a total of twenty analyses using these solutions the percentages of sulfur actually found ale given in Table I. Also included in this table are the normality of the nitric acid used and the actual weight of the barium sulfate obtained from 10 ml. of sample. A statistical analysis of these twenty deteiminstions reveals that the standard deviation is 0.049 gram, from which it may be calculated that the probable error is 0.033 gram. The arithmetic mean of the weight of the precipitates is 1.22 grams, differing by 1.7% from the value of 1.20 grams obtained using the oxygen bomb method. It may be concluded that the probable value for any single determination is 1.22 =k 0.03 gram, correrecent report sponding in per cent of sulfur t o 1.88 2 0.04%. [-1 (11) on a colorimetric method for the determination of thiophene revealed a 15 t o 20% error using the photoelectric colorimeter and up t o a 30% error for the visual colorimeter.] Although it is generally considered desirable t o rid the solution of nitrate prior t o the precipitation of sulfate, no significant differences in results could be noted when the ienioval of nitrate by evaporation with small portions of concentrated hydrochloric acid was omitted. The error caused by such coprecipitation is smaller than the probable error of this method. I n this connection, it was recently found ( 6 ) , in the course of numerous determinations of sulfuric acid in the presence of nitric acid, that the high results due t o coprecipitation of barium nitrate did not exceed 1yo. It was deemed advisable t o test the present method in the analysis of samples of much lower sulfur content. Bccordingly, samples of thiophene in cyclohexane were prepared containing 0 . 3 i % and 0.18% sulfur by weight. The results obtained are given in Table 11. The oxidation of thiophene has been shown t o give rise t o some oxalic acid ( l 7 ) ,and in order t o preclude the possibility of the precipitate’s containing any barium oxalate which would subsequently be ignited t o the oxide and weighed along with the sulfate, 1 gram of oxalic acid Jvas added t o each of two runs, but, as may lie seen from Table I (samples 11 and la), no significant differenre in the weight of the baiium sulfate precipitate was observed.
Angeli, A , , and Ciamician, G., Ber., 24, 74, 1347 (1891). Ball, J. S.,U. S. Bur. M i n e s , R e p t . Invest., 3591, 50 (1942). Claxton, G., and Hoffert, TT’. H., J . SOC.Chem. Ind. ( L o n d o n ) , 6 5 , 333 (1946).
Cullinane, N. M., and Davics, C . G., Rec. trau. chim., 5 5 , 881 (1936).
Deniges, G., Bull. soc. chim., Fiance, [3] 15, 1064 (1896). Goddard, D. R., Hughes, E. D., and Ingold, C. K., J. Chem. SOC.,1950,2575.
Hinsberg, O., Ber., 48, 1611 (1915). Lanfrey, M., Compt. rend., 153, 73 (1911). Ibid., 154, 519 (1912). Liebermann, C., Ber., 20, 3231 (1887). McKee, H. C., Herndon, L. K., and Withrow, J. R., AXLL. CHEM.,20, 301 (1948). Meyer, A., Compt. rend., 169, 1402 (1919). Mixer, R. Y., Chem. Eng. News, 26, 2434 (1948). Noller, C. R., “Chemistry of Organic Compounds,” p. 2G8, Philadelphia, W. B. Saunders Co., 1951. Ibid., p. 274, Schwalbe, C., J. SOC.Chem. Ind. ( L o n d o n ) ,24,988 (1905). Sernagiotto, E., Atti accad. nazl. Lincei, 28, I, 432 (1919). Whitmore, F. C., “Organic Chemistry,” p. 33, New York, D. Van Nostrand Co.. 1951. RECEIVED for review September 13, 1951. Accepted September 26,
1952.
Abstracted from t h e thesis t o be siihmitted by Leonard 9. Levitt t o t h e Graduate Council of Temple Univeisity in partial fulfillment of the requirenients for the Ph.D. degree.
CORRECTIONS Food I n the review on “Food” [Natchett, J. R.. and von Loesecke, -4~7.4~. CHEM., 24, 242 (1952)l reference (61) should read: (61) Food Processing, 12 (IO), 46 (1981).
H. If7.,
Estimation of Sodium Triphosphate I n the article on “Estimation of Sodium Triphosphate” [Bell, . 24, 1998 (1952)] the last line Wreath, and Curless, ~ ~ N A LCHEU., in the first column under Procedure should read “betn-een 2G and 28 ml. of sodium hydroxide.”
Determination of Free Acid in the Presence of Hydrolyzable Ions I n the article on “Determination of Free Acid in the Presence of HydrolyzableIons” [Pepkowitz, Sabol, and Dutina, ANAL.CHEhr., 24, 1956 (1952)l the titles of Figures 2 and 4 have been interchanged. They should read : Figure 2. Conductometric Titration Cell. and, Figure 4. Complexing .-lction of Sodium Fluoride.
