On the basis of a study of the effect of light on an anode it is suggested that electrolytic oxidation of the SCN− ion in molten thiocyanates proceeds in two ways according to experimental conditions: The primarily formed thiocyanate radicals either polymerize to chemically stable parathiocyanogen , or they interact with anions of the melt forming trithiocyanate ion which is oxidized to polytrithiocyanogen , a chemically unstable species showing semiconductor photoresponse to light.