I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
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Since the authors' results indicated that there was a noticeable difference between the amount of mercaptan sulfur found after treatment of the Stoddard solvent containing elementary sulfur with metallic mercury and that amount which is actually present in the material, i t is advisable not to remove the free sulfur prior to the mercaptan sulfur determination but to titrate the mercaptan sulfur present in the Stoddard solvent directly with silver nitrate. T h a t the elementary sulfur has no effect on the determination of mercaptan sulfur in the Stoddard solvent is shown b y Table VI. The deviations from the amounts of mercaptan sulfur actually present as shown in Table VI are all within the limits of experimental error, showing that i t is justifiable to determine the mercaptan sulfur content of Stoddard solvent (or other hydrocarbon material) by titration with silver nitrate without removal of elementary sulfur present in the material under test. Where a considerable quantity of elementary sulfur is present, the color of the precipitate obtained during titration of the mercaptans with silver nitrate solution may pass through various shades of orange, red, or brown and persistent emulsions may be formed. The addition of quantities of 95 per cent alcohol as high as 100 cc. may be necessary to break these
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emulsions and bring the precipitate into the interface so that the color of the solution may be noted.
Summary and Conclusions Contrary to the current practice of removing elementary sulfur by means of metallic mercury before determination of the mercaptan sulfur content of gasolines or naphthas, the determination of the mercaptan sulfur content should be made on the initial gasoline or naphtha, ignoring any elementary sulfur which may be present. Certain mercaptans are adsorbed by mercuric sulfide, resulting in such cases in low values for the mercaptan sulfur content of the naphtha which has been agitated with mercuric sulfide. Any loss of mercaptans which might take place on filtration of Stoddard solvent solutions through K h a t m a n S o . 40 filter paper or on normal agitation of such solutions with air is within the limits of experimental error of the mercaptan sulfur determination.
Literature Cited (1) Borgstrom, P., and Reid, E. E., IND. ESG. CHEM.,-4nal. Ed., 1, 186 (1929). ( 2 ) Greer, E. J., ISD. ENG.CHEM.,21, 1033 (1929). and ilnding, C. E.. J r . , Ibid., I n a l . Ed., 7, 86 (3) Malisoff, W. M.,
(1935).
Determination of Water in Benzene J. H. SIMONS AKD E. 31. KIPP, School of Chemistry and Physics, The Pennsylvania State College, State College, Penna.
A solution of sodium triphenylmethyl in ethyl ether has been investigated as a reagent for the analysis of water in solution in benzene. The analyses have been made on samples containing a relatively small concentration of water. The color change of the reagent is used as the indicator, and relatively high precision is obtainable on low water concentrations. The reagent is suitable for the analysis of other substances.
A
SUMBER of ingenious methods have been devised for
the analysis of water dissolved in benzene and other organic liquids-for example, the use of calcium carbide (3) with the determination of the acetylene produced; the use of calcium hydride (8) with the determination of the evolved hydrogen; the use of alpha-naphthoxydichlorophosphine (1, 7) with titration of the hydrogen chloride; the use of a reagent consisting of liquid sulfur dioxide and iodine dissolved in anhydrous methyl alcohol (4), where the reagent reacts with water forming sulfuric and hydroiodic acids, which are caused to combine with pyridine, and the excess iodine is determined; and the determination of the solubility of silver perchlorate (6) which varies with the water content of benzene. The authors have used a solution of sodium triphenylmethyl dissolved in ethyl ether for the determination of water in solution in benzene. Bent and Lesnick (Z), who used this reagent to determine the amount of water adsorbed on glass surfaces, indicate that the partial pressure of water in equilibrium with this substance is very low and that equilibrium is reached rapidly. In order to obtain samples of benzene containing reproducible concentrations of water, a stream of
nitrogen containing a known partial pressure of water was passed through dry benzene. The titration with the standardized reagent was accomplished without removing the sample from the apparatus. The standardization was also done within the apparatub by means of a
