D i m e t h y l g l y o x i m e was used b y Braley and Hobart 1 as an analytical reagent for cobalt following the researches of Tsehugae/] 2 on metallic derivatives of dioximes. Compounds containing a m m o n i a or pyridine were studied, and the brown colorations p e r m i t t e d to detect as little as 5 ~ of cobalt. Using the same reagent combined with alkaline sulfides, Feigl and von Tustanowska 3 obtained a violet red coloration which allowed t h e m to detect cobalt ion in a dilution of 1 to 830000. Bertrand and Machebeu] 4 developed a colorimetrie m e t h o d for the determination of cobalt in biological materials. Charottino ~ replaced a m m o n i a b y certain amines, chiefly aromatic ones (benzidine), and claimed to have thus increased the sensitivity of the test, which was confirmed b y Braun ~. Finally, b y the use of toluidine, Spacu and Macaronici 7 attained a still higher sensitivity. Table 1. S e n s i t i v i t y of T e s t .
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