CHELATES OF BETA-DICARBONYL COMPOUNDS AND THEIR DERIVATIVES .16. THIODIBENZOYLMETHANE AS A PHOTOMETRIC AND GRAVIMETRIC REAGENT FOR COBALT EXTRACTION

Cobalt(II) salts react rapidly with monothio-β-diketones to form cobalt(III) chelates. At low temperatures and under anaerobic conditions, cobalt(II) chelates of thiothenoyltrifluoracetone and thioisobutyrylacetone can be isolated; their magnetic behaviour indicates a tetrahedral structure. The use of thiodibenzoylmethane for the extraction-photometric determination of cobalt is described. Owing to the considerable kinetic stability of the formed cobalt(III) chelate, interfering metals can be separated by reextraction with sodium hydroxide solution containing cyanide, except in the case of copper. Thiodibenzoylmethane is also suitable for the gravimetric determination of cobalt in the range 2-15 mg. In the presence of thiourea, copper and manganese do not interfere in up to 10-fold amounts; zinc can be kept in solution by means of ammonia and ammonium thiocyanate, but iron must be separated by ether extraction. © 1969.