The phenomenon of the electrochemiluminescence on the polished platinum cathode in the acid and basic aqueous solutions of the potassium peroxydisulfates was studied. It is determined that the electrochemiluminescence intensity increases with the oxygen saturation of the solution. It is proposed that the emitter of the light radiation is an oxygen in the (1) Delta(g) singlet state, that was verified by spectral investigations. A probable scheme of the singlet oxygen formation in the solution, and results of the electrochemiluminescence spectral investigation are discussed.