QUALITATIVE DETERMINATION OF FERROCYANIDE ION WITH QtJINONE CHLOROIMIDE EUGENE W. BLANK
Colgote-Palmoliue-PeetCompany, Jersey City, New Jersey
THE usual tests for ferrocyanide ion involve the use of uranyl acetate, ferric chloride ( I ) , and titanium tetrachloride ( 2 ) . The few organic reagents recorded in the literature include quinoline hydrochloride, henzidine hydrochloride, and indigo carmine (3). It has been found that quinone chloroimide (0 : CsH4: NCl) gives a characteristic color reaction with ferrocyanide ion, permitting positive identification of the latter either alone or in the presence of femcyanide ion. The presence of strong oxidizing agents interferes with the test. The alcoholic quinone chloroimide solution darkens on standing and should be freshly prepared for use immediately prior to making the test. PROCEDURE
Prepare a 0.5 per cent solution of quinone chloroimide' in ethyl alcohol. Quinone chloroimide, Eastman Practical, m. p. 75'-78T (Purified by steam distillation.)
Place 0.5 ml. of the neutral or slightly acid solution under test in a depression of a white porcelain spot test plate. Add 5 drops of the 0.5 per cent alcoholic quinone chloroimide solution. In the presence of ferrocyanide ion an emerald green color will develop in 15 to 30 seconds. Stronger concentrations of test reagent and test solution result in the formation of a dark brown precipitate. When carried out in this manner the test will detect 5 y of potassium ferrocyanide. LITERATURE CITED
(1) FEIOL, "Qualitative analysis by spot tests," translated by M ~ m e w s Nordemann , Publishing Company, Inc., New York City, 1937, p. 176. (2) OELKE,Ind. Eng. Chem., Anal Ed., 12, 498 (1940). (3) "Tables of reagents for inorganic analysis," First Report of the International Committee on New Analytical Reactions and Reagents of the Union internationale de Chimie, Akademische Verlagsgesellschaft M. B. H., Leipzig, 1938, p. 347.
