Determination of phenylmercury chloride in the presence of methylmercury chloride

The kinetics of the isotope exchange between phenylmercury chloride and inorganic radiomercury has been investigated in aqueous solutions, in benzene and in benzene-hydrochloric acid systems. Extremely slow isotope exchange between methylmercury chloride and inorganic radiomercury in hydrochloric acid solutions allows the very simple and rapid radiochemical determination of phenylmercury chloride in the presence of a great excess of methylmercury chloride. Half-lifes of isotope exchange between C6H5HgCl and 203HgCl42- in 3M hydrochloric acid depend on the reciprocal of the concentrations of both species. The rate of isotope exchange does not depend on the concentration of hydrochloric acid in the range 0.1-3.0 M where mercury is present as a neutral (HgCl2) or anionic complexes (HgCl3- and GhCl42-). The rate of isotope exchange between C6H5HgCl and 203HgCl2 in benzene is practically the same as in hydrochloric acid solution k1.5+-0.2x103 mole-1dm3s-1 at 25 degC however, the heterogenous isotope exchange between C6H5HgCl in benzene and 203HgCl42- in 3M hydrochloric acid is slower: for a bimolecular reaction k= 13.1+-0.5 mole-1.dm3.s-1 at 25 degC. The isotope exchange between CH3HgCl and 203HgCl42- (or 203HgCl2) in 0.1-3M hydrochloric acid is extremely slow; practically no exchange has been observed after some hours. (T.I.)