Studies on 3,3′-dichloro-, 4,4′-dichloro- and 5,5′-dichloro,2-2′-dimethyldithizone and their reactions with metal ions

Three new derivatives of dithizone are reported, with their electronic and i.r. spectra, acidity constants and partition coefficients between 0.5 M sodium perchlorate and chloroform or carbon tetrachloride. The extraction equilibria with Cd, Co(II), Hg(II), Ni, Pb, Tl(I), Zn and Bi and the spectrophotometric characteristics of the extractable metal chelates are described. Complete extraction of these complexes requires higher pH than that needed with dithizone itself. The 4,4′-dichloroisomer is more efficient than the 3,3′ and 5,5′-isomers, or dithizone itself, for the separation of cadmium from zinc or cobalt from nickel.