コバルトの電解分析

概要

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Electrolysis of Co in ammonia alkaline solution gives usually the deposition of Co oxide on the cathode and the quantitative electrodeposition of metallic Co is difficult. This abnormal excessive deposition cannot be suppressed by means of reducing agents such as hydrazine sulfate. It was found by the authors that when sodium pyrophosphate-NH4OH solution or ammonium carbonate-NH4OH solution was used as an electrolyte, there was no great error due to an excessive deposition of Co oxide and the quantitative electrodeposition of metallic Co was obtained within an error of 0.01%. The constituent of electrolyte and the conditions for the electrolysis were as follows: CoSO4 (1g as Co equivalent). 10g (NH4)2SO4. 10g sodium pyrophosphate or 10g ammonium carbonate. NH4OH enough to dissolve the precipitate and then 05ml in excess. The temperature of electrolysis at 4560°C. Current density at 0.25 amp/dm2. Time required for electrolysis is about 20 hrs. The interferences of coexisting elements, errors produced by dissolution and deposition of Pt as the electrode were discussed.
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