The precipitation of sparingly-soluble metal chromates from aqueous solution in the presence of chelating organic anions: Induction periods and nucleation rates

The precipitation of barium, zinc, lead, copper and silver chromates was studied in the presence of the chelating organic anions gluconate, tartrate, citrate, aspartate, glutamate and E.D.T. Aate. Generally, these chelators complex the metal cation and reduce the free metal cation and mean metal chromate concentrations in solution. The rates of nucleation with microcrystallite formation were then markedly reduced and the induction periods increased from below 1 sec to well above 100,000 sec with increasing chelator/cation concentration ratio; the experimental results were expressed by the relations; The coefficients F at any metal chromate concentration were related in turn to the stability constants of the metal-chelator complexes.