The precipitation of cadmium sulphide in aqueous solutions

Abstract

The spontaneous precipitation of cadmium sulphide in aqueous supersaturated solutions has been investigated at 25 °C. In all cases, an induction period, inversely proportional to the solution supersaturation, preceded the onset of precipitation. α-CdS (greenockite) was identified as the only phase being formed. The rates of precipitation were proportional to the solution supersaturation and were affected by the presence of anions arising from the cadmium salts employed in the preparation of the supersaturated solutions. The presence of SO^2–₄ ions resulted in higher precipitation rates, and the effect of NO^–₃, Cl^–, Br^– and I^– was also investigated. A fourthorder dependence of the rates of cadmium sulphide precipitation on the solution supersaturation, typical of several sparingly soluble salts, was found.