The use of electrolytically generated pentavalent molybdenum as a coulometric titrant has been studied.The current efficiency for the electrogeneration of molybdenum (V) at a platium cathode in sulfuric acid media was found to be a function of the generating current density and the concentration of haxavalent molybdenum in various concentration of sulfuric acid.With 4.5M sulfuric acid containing 0.1M ammonium molybdate the generation of molybdenum (V) is of 100 percent efficiency up to a current density of 1-10 milliamp/cm².With this medium milligram quantities of cerium, chromium and vanadium can be titrated coulometrically with an average error of about ±0.2 per cent or less.Cooke's modified potentiometric method was used for end-point detection.In the presence of copper, the test solution must be free from air by bubbling with and titrating under nitrogen, as copper catalyzed the aerial oxidation of molybdenum(V).