INDu
606
sT R I AL
AND ENGI
TABLE 111. SOLUBILITY OF COMMERCIAL SULFURPRODVCTS IN BUTYLCARBITOL AT 25.0” C. Product
Equilibrium Concentration Approached from
Solubility of Sulfur
Supersaturated s o h . Unsaturated soin. Supersaturated aoln. Unsaturated soln.
2.18 2.21 2.14 2.26
Unsaturated eoln. Unsaturated s o h . Unsaturated soln.
2.34 2.15 2.20
G./L Recrystallized
C.
P. sulfur
Mike sulfur Koppers 5otation paste (dried a t 900 C.) Stauffer’spaste (dried,& 90’ C.) Stauffer’s dry magnetlc 70 paste
T o determine whether commercial sulfur products contained appreciable quantities of interfering materials, the solubility of several of these products in the monobutyl ether of diethylene glycol was determined. This solvent, known commercially as butyl carbitol, may be substituted for acetone throughout the analytical procedure and the amount of sulfur in solution determined b y this method. The results in Table I11 show that no appreciable interfering materials occur in the commercial fungicides tested and that the solubility of the sulfur in them is equivalent t o that of recrystallized c. P. sulfur.
~ E RE I N G
cH E M I sTRY
Vol. 14, No. 7
Literature Cited Emerson, H., J . Am. Chem. Soc., 52, 1291 (1930). Evans, A. C., and Martin, H., J. Pomology Hort. Sci., 13, 261 (1935). Fitch, H. W., Phytopathology, 16,427 (1926). Fleck, R. H., and Ward, A. M., Quart. J . Pharm. Pharmacol., 7, 179 (1934). Heinemann, G., and Rahn, H. W., IND.ENQ.CHEM.,A.v.4~. ED., 9, 458 (1937). Krause, W., Chemist-Analyst,27, No. 1, 14 (1938). Kuhl, F., 2. anal. Chem., 65, 185 (1924). Mano, G. G., and Kirk, P. L., IND.ENG. CHEM.,ANAL.ED., 9, 198 (1937). Pierce, J. A., Ibid.,1, 227 (1929). Small, C. G., Phytopathology, 24, 296 (1934). Thatcher, R. W., and Streeter, L. R., New York Agr. Expt. Sta. Tech. Bull. 116 (1925). Von Nagy Ilosva, L., Ber., 32, 2697 (1899). Wilson, C. W., and Kemper, W. A., IND.ENQ.CHEM.,ANAL. ED., 10, 418 (1938). Woodward, G., Ibid.,1,117 (1929). Zahn, V., Ibid.,9, 543 (1937). PRESIDNTED before the Division of Agricultural and Food Chemistry a t the CHEMICAL SOCI~TY Atlantic , City, N. J . 102nd Meeting of the AMERICAN Approved by the Director of the New York dtate Agricultural Experiment Station for publication as Journal Paper N o . 504.
A New Microtest for Iodide
A
LTHOUGH most chemical analyses depend upon the possibility of chemically converting the constituents to be detected into another characteristic form, the sensitivity of these chemical tests which depend upon a characteristic precipitate, gas, or colored or fluorescent solution is necessarily limited by the physical constants involved and the personal equation of the observer. However, by making use of catalyzed reactions, extremely small amounts of substances can be detected. Thus, in the detection of iodide, the use of catalyzed reactions has been very successful. Feigl and Frankel (4) developed a method for detecting the presence of 0.05 microgram of iodide in a concentration of 1 part per million, based on the conversion of o-nitroaniline, its isomers, or other primary aromatic amines to form a diphenyl derivative with bromobenzene in the presence of cuprous iodide or a mixture of copper and potassium iodide. Using the catalytic effect of iodide upon the ceric-arsenite oxidation-reduction reaction, Kolthoff and Sandell (6) showed that 0.05 microgram of iodide can be detected in a concentration of 1 part in 500,000 (3). The authors have also presented a method (6) for detecting iodide by its catalytic effect upon the nitrite-arsenite oxidation-reduction reaction, whereby 0.2 microgram of iodide can be detected in a concentration of 1 part in 500,000. Continuing their work on the detection of halides, the authors have developed a new, simple, and rapid microtest for iodide, which is based upon the catalytic effect of iodide on the nitratearsenite oxidation-reduction reaction and may be carried out in a small test tube or on a spot plate. A search of the literature revealed no mention of this effect, except where it was applied to the manufacture of arsenates by the oxidation of arsenious oxide with nitric acid. Smith and Miller (81, investigating the inhibitory effect of mercury on this reaction, showed that hydrochloric, hydrobromic, and hydriodic acids will act as catalysts. Shortly before this, Behse was granted a patent (1) for the manufacture of arsenic acid by means of nitric acid usin hydrochloric acid as a catalyst. Later, Latimer (‘7) obtainef a atent in which iodide was used as a catalyst. He also claimefthat the other halogens, chloride, bromide, and fluoride, could be used as catalysts but that much greater concentrations of these were required.
DAVID HART A N D ROBERT RlEYROWITZ Brooklyn College, Brooklyn, N. Y.
Since both bromides and chlorides catalyze this reaction, conditions had to be obtained under which moderate amounts of these anions would not interfere in the detection of relatively small amounts of iodide. Using the procedure described below, the authors were able to detect 1.0 microgram of iodide in a concentration of 1part in 50,000. The presence of 500 micrograms of either thiocyanate, bromide, chloride, or a mixture of these anions does not catalyze this reaction in this procedure. Other anions of the silver nitrate group which are likely to interfere-cyanides ferricyanides, ferrocyanides, and sulfides-are removed in the usual way ( 2 ) with cobalt nitrate.
Frocedure for Detection of Iodide To a small test tube (or a spot plate) containing 1 drop of the solution to be tested, add 1 drop of M sodium arsenite and 2 drops of water and mix thoroughly. Add 2 drops of concentrated nitric acid and allow to stand for 3 minutes after complete mixing. Next add 3 drops of 0.5 M silver nitrate, stir the mixture thoroughly, and add 1.5 M sodium carbonate dropwise. The formation of a red-brown precipitate of silver arsenate shows the presence of iodide. If the precipitate is yellow (due to silver arsenite), iodide is absent.
Literature Cited (1) Behse, 0. C., U. S. Patent 1,493,798 (May 13, 1924). (2) Curtman, L. J., “Qualitative Chemical Analysis”, p. 434, New York, Macmillan Co., 1938. (3) Feigl, F., “Qualitative Analysis by Spot Tests’’, p. 168, New York, Nordemann Publishing Co., 1939. (4) Feigl and Frankel, 2. anal. Chem., 91, 12-14 (1932). (5) Hart and Meyrowita, IND.ENG. CEEM., ANAL.ED., 12, 774-5 (1940). (6) Kolthoff and Sandell, J . Am. Chem. Soc., 56, 1426 (1934). (7) Latimer, J. N., U. S. Patent 1,974,747 (Sept. 25, 1934). (8) Smith and Miller, IND.ENG.CHEM.,16, 1168-71 (1924).
