Electrolytic coloration of O22−-doped NaCl crystals

O22−-doped NaCl crystals are colored electrolytically by using a pointed cathode and a flat anode at various temperatures and voltages, which mainly benefit from appropriate coloration temperatures and voltages as well as anode structure of used electrolysis apparatus. Characteristic OH−, U, V2m, UA, V2, V3, O2−–Va+ complex, F, R1, R2 and M absorption bands are observed in absorption spectra of the colored crystals. Production and conversion of color centers in electrolytic coloration is explained. Current–time curves for electrolytic colorations and their relationships with electrolytic colorations were given.