Determination of nickel, cobalt and copper by direct photometric titration with cyanide

Abstract

Nickel(II), cobalt(II) and copper(II) at the 0.1 M level are titrated photometrically with cyanide in ammoniacal solution. The nickel-cyanide reaction shows reproducible 1 : 4 stoicheiometry and can be used for titration. The reaction with cobalt shows firm 1 : 5 stoicheiometry but is complicated by formation of oxygen-containing species. The reaction with copper shows uncertain stoicheiometry of about 1 : 4. In the nickel titration zinc does not interfere but cobalt and copper add on, both showing 1 : 4 metal-cyanide stoicheiometry.