COMPLEX COBALT PERIODATES

Abstract

A number of complex cobalt periodates have been prepared. Sodium periodatocobaltate (III) Na₅H₂Co(IO₆)₂.10H₂O is obtained as green crystals when cobaltous and periodate ions react in the presence of alkaline sodium hypochlorite. Somewhat similar potassium, barium, and lanthanum salts are described. Various methods of demonstrating that the cobalt is trivalent, including the observation that sodium periodatocobaltate (III) is diamagnetic, are described. The free acid H₇Co(IO₆)₂ can be obtained in solution, and measurements have been made on its ionization constants. Observations have been made on the stability of these compounds, and the stability constant of the periodatocobaltic ion (in alkaline solution at 60 °C) has been shown to be in the neighborhood of 10¹⁸.