The electrogenerated chemiluminescence (ecl) produced in acetonitrile-water solutions (1: 1 by volume) by the reaction of electrogenerated Ru(bpy),+ with the strongly oxidizing intermediate, SO4--, generated during reduction of S208” is described. The orange luminescence (A, = 625 nm) corresponds to emission from R~(bpy) ,~+*. The relative ecl intensity is a function of S20s2concentration, and ...