Cobalt Disulphide, CoS₂

Setterberg believed that this Cobalt Disulphide, CoS₂ results on heating cobalt monoxide to redness, either in contact with sulphur or in a current of hydrogen sulphide. The mass is treated with dilute hydrochloric acid, leaving an unstable residue of disulphide. Moist air oxidises it to the sulphate, whilst the application of heat expels some of the sulphur.