JANUARY 15, 1936
ANALYTICAL EDITION
elements. It is only in the oxidizing flame that the color is apparent. Borax and phosphate bead tests yield with rhenium a gray color in a reducing flame. I n the outer cone the color or turbidity, due to metallic rhenium, disappears as a result of oxidation. Colorimetric Detection The colorimetric determination of rhenium as developed by Geilmann, Wrigge, and Weibke (12) is by all odds the most convenient laboratory test available for the rapid detection of heptavalent rhenium. The Geilmann reaction is brought about by adding to a hydrochloric acid solution of a perrhenate, stannous chloride and ammonium or potassium thiocyanate. A yellow-brown thiocyanate is produced which is soluble in ether, butyl acetate, and cyclohexanol. The complex is insoluble in carbon bisulfide, carbon tetrachloride, methyl cyclohexane, and aniline. Commercial malonic ester, methyl salicylate, resorcinol, benzyl alcohol, furfural aldehyde, and acetoacetic ester extract the color but for various reasons are not satisfactory. Although the reaction is subject to numerous influences which must be controlled before it is satisfactory as a quantitative determination ( I ) , it is of great value as a qualitative test. The same reaction is, however, characteristic of molybdenum and unless this element is known to be absent the reaction cannot be considered specific. Although a number of extractors have been investigated in this laboratory, no water-insoluble substance has been found which does not extract both the rhenium and the molybdenum complexes about equally well. During the course of a study on the determination of rhenium in ores, minerals, and industrial concentrates (16) it was found that, whereas ethyl xanthate reacted with molybdic acid to yield a violet-red chloroform soluble complex, rhenium did not. TABLEVI. DETECTION OF RHENIUM IN PRESENCE OF MOLYBDENUM
Rhenium Taken
Molybdenum Added
A parent Rgenium Recovery
Y
r
Y
1 .5. 0 _.
200 200 250 300 00 150 200 200 300 00 250 100 150 150 60 100
50
so m --
100 100 100 200 200 300 300 300 400 500 1000 1000 1000 1000
143 218 216 242 255 04.7 143 214 210 308 55.2 273 108 164 139 57.1 110
Error
%
- 4.7
++ 810 8.0 - 3.2 -15.0 f 7.8 - 4.5 4- 7.0 5.0
++, 2.7
- 8.0
4- 9.2
f 8.0 9.3
+- 7.3 - 4.8 $10.0
It was found that if solutions containing molybdenum and rhenium were first treated with ethyl xanthate and the molybdenum complex was removed with chloroform, rhenium could be determined with fair accuracy in the remaining solution. Neither stannous chloride, hydrochloric acid, ammonium thiocyanate, nor mixtures of the three produced a color with residual traces of the xanthate. Although the accuracy of the method is such that it is not satisfactory without refinement for quantitative work, it serves rather well for qualitative detection. Table VI gives data illustrative of results which were obtained. Analysis for rhenium was made as described by Geilmann, Wrigge, and Weibke (12) after molybdenum had been extracted as a xanthic acid complex with chloroform. The data presented were obtained while working on solutions free from metals other than molybdenum and rhenium.
15
Iron and copper are known to interfere. Oxidizing agents, excessive amounts of reducing agents, and high salt conoentrations contribute to erratic results. Phenyl hydrazine and thioglycolic acid both react with molybdenum but not with rhenium. Although like ethyl xanthate they are known to be unsatisfactory for the determination of molybdenum, an attempt was made to develop a satisfactory method which would allow the removal of the molybdenum so that rhenium could be determined in the residual solution. They were found to be unsatisfactory and inferior to ethyl xanthate. Literature Cited (1) Babler, senior thesis, University of Wisconsin, 1935. (2) Briscoe, Robinson, and Stoddart, J . Chem. Soc., 666 (1931). (3) Geilmann and Briinger, 2. anorg. allgem. Chem., 199,77 (1931). (4) Geilmann and Hurd, Ibid., 213,336 (1933). (5) Ibid., 213, 337 (1933). (6) Ibid., 214, 261 (1933). (7) Geilmann and Voigt, Ibid., 193, 311 (1930). (8) Geilmann and Weibke, Ibid., 199, 120 (1931). (9) Ibid., 195, 289 (1931). (10) Ibid., 199, 347 (1931). (11) Geilmann and Wrigge,Ibid., 199, 65 (1931). (12) Geilmann, Wrigge, and Weibke, Ibid., 208, 218 (1932). (13) Heyne and Moers, Ibid., 196, 129 (1931). (14) Hurd, L. C., J. Chem. Ed., 10, 605 (1933); Loring and Druce, Chem. News, 131,337 (1925). (15) Hurd and Reynolds, unpublished research, University of Wisconsin, 1934. (16) Kao and Chang, J.Chinese Chem. Soc., 2 , 6 (1934). (17) Kraus and Steinfeld, 2. anorg. allgem. Chem., 193,385 (1930). (18) Laing, J., senior thesis, University of Wisconsin, 1932. (19) McAlpine and Soule, “Qualitative Chemical Analysis,” New York, D. Van Nostrand Co., 1933. (20) Meggers, Bur. Standards J. Research, 1027 (1931). (21) Muller and LaLande, J. Am. Chem. Soc., 55,2376 (1933). (22) Noddack, I. and W., “Das Rhenium,” Leipzig, Leopold VOSS, 1933. (23) Noddack, I. and W., Ergebnisse exakt. Naturw., 6,354 (1927). (24) Noddack, I. and W., 2. anorg. allgem. Chem., 1 8 1 , l (1929). (26) Noddack, I. and W., 2.phus. Chem., 125,268 (1927). (26) Ibid., 154, 207 (1931). (27) Noddaok, W., 2. Elektrochem., 34,627 (1928). (28) Noddaok, W., Tacke, I., and Berg, O., Sitzber. preuss. Akad. Wiss., 19, 400 (1925). (29) Noyes and Bray, “System of Qualitative Analysis of the Rarer Elements,” New York, Macmillan Co., 1927. (30) Rau, senior thesis, University of Wisconsin, 1934. (31) Reinders and Hurd, unpublished research, University of Wisconsin, 1935. (32) Scharf and Spiering, senior thesis, University of Wisconsin, 1934. (33) Tougarinoff, B., Bull. soc. chim. Belg., 43, 111 (1934).
RECEIVED August 8, 1935. Presented before the Division of Phyaical and Inorganic Chemistry at the 89th Meeting of the American Chemical Society, New York, N. Y., April 22 to 26, 1935.
A Color Reaction for Detection of Cyclopentadiene BORIS N. AFANASIEV, Sibirsky 50, Sverdlovsk 26, U. S. S. R.
S
MALL quantities of cyclopentadiene can be detected as follows: One drop of the liquid to be tested is mixed with 1 cc. each of chloroform and glacial acetic acid and then treated cautiously with 2 or 3 drops of concentrated sulfuric acid. As little as 0.1 mg. of cyclopentadiene gives a distinct violet coloration, Some higher boiling terpenes give a similar coloration but only with acetic anhydride, chloroform, and sulfuric acid. RECEIVED November 30, 1935.
