Cobalt Sesquisulphide, Co₂S₃

Cobalt Sesquisulphide, Co₂S₃, results when a mixture of sulphur and the carbonates of cobalt and potassium are raised to white heat. Nickel, in similar circumstances, yields double sulphides such as K₂S.3NiS, and thus resembles palladium and platinum, whilst cobalt behaves more like rhodium and iridium. The position of cobalt before nickel in the Periodic Table is thus supported.