The separation of alkali metal ions by electrophoresis on paper impregnated with ammonium molybdophosphate has been investigated.Aqueous solutions of ammonium nitrate and nitric acid as electrolyte,have proved to be successful in separating potassium,rubidium,and cesium from each other in a single step by this technique.By using 0.2 to 0.5 M NH₄NO₃ and 0.1 M HNO₃ as electrolyte,at an electric field of 6.3-12.5 V/cm,with migration period from 50 to 100 minutes,a good separation of potassium,rubidium,and caesium is obtained.For example,when the concentrations of ammonium nitrate and nitric acid are kept at 0.4 M and 0.1 M respectively,with an electric field of 8.4 volts per centimetre,for 1 hour,the migration distances are: K-9.8;Rb-2.5;Cs-0.1 cm.