Cobalt blue iodide

Modras (51) reported spot test reactions to differentiate hydralazine from closely related drugs. Reagents used were aqueous copper (I) chloride, aqueous ammonium molybdate, iodine in potassium iodide solution, aqueous cobalt (II) nitrate, alcoholic ninhydrin, and alcoholic bromophenol blue. The tests were performed on paper or on Silica Gel G. 

That is, a mixture of 1-, 2-diaquo-tetrammino-cobaltic chloride and 1-, 2-diehloro-tetranimino-cobaltic chloride is formed. The aquo-salt is readily soluble in water but the diehloro-salt sparingly so. The last named forms intense blue crystals which are contaminated with small quantities of the praseo-salt, from which it may be freed by transforming it into the dithionate. The dithionate is practically insoluble, but the chloride may be regenerated from it by rubbing it with ammonium chloride. The bromide, the iodide, and the nitrate have all been prepared. 

PROCEDURE Dissolve mixtures of cobalt(II) chloride and various quantities of sodium or potassium bromide and iodide in water. Iron(III) chloride can also be used. Use a paint brush to make water color paintings on paper (filter paper works very well). With some experimentation, water color paintings which encompass a wide variety of colors (yellow, pink, green, blue) can be made which appear when heated and disappear in a humid atmosphere.( to) These solutions can be kept for the next year, or, since they contain very little cobalt, disposal in the trash is appropriate. The salts can be washed off the paper and the cobalt recovered from the resulting solution. 

They are, however, still substantially lower than the values for the reactions with hydroquinone and iodide ion which are thought to be outer-sphere. The oxidation of variamine blue, iV-(/>-methoxyphenyl)phenylenediamine (L), has been studied in an excess of cobalt(iii) under anaerobic conditions. The reaction is biphasic, with a rapid initial step yielding Co , The rate law is essentially similar to equation (3) although there is some deviation from pseudo first-order behaviour even at very high oxidant concentrations. The overall reaction may be expressed as involving the protonated ligand,... 

The mobile phase diisopropyl ether-benzene-tetrahydrofurane-n-hexane (10 7 5 11) was used in one direction and tetrahydrofurane-/i-hexane (2 3) in the other direction on silica gel 60 plates without fluorescence indicator. Visualization was based on enzyme inhibition with cholinesterase, with butyrylthiocholine iodide serving as the substrate. After spraying with cobalt chloride, the enzyme inhibiting substances appeared as blue spots against a white background. The limit of detection was between 15-1(X) pg. (65a). 

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