In 1659 a German chemist , J.R. Glauber , melted a mixture of the mineral pyrolusite and potassium carbonate to obtain a material that made a green solution ( potassium manganate ) when dissolved in water . It slowly changed color to violet ( potassium permanganate ) and then finally red . In 1659 , Johann Rudolf Glauber fused a mixture of the mineral pyrolusite and potassium carbonate to obtain a material that , when dissolved in water , gave a green solution ( potassium manganate ) which slowly shifted to violet and then finally red .