Electrochemical oxidation of americium (3) in phosphoric acid solutions in acetonitrile

Electrochemical oxidation of americium (3) in acetonitrile solutions containing 0.3-2.0 mol/l H3PO4 is investigated. With anode potential +1.4 V (relatively mercury-sulphate electrode) americium for half an hour is completely oxidized to americium (4). Oxidation takes place both in pure acetonitrile solutions and in aqueous-acetonitrile solutions with the water content to 50%. In staying americium (4) in acetonitrile solution is constantly reduced to americium (3) according to first-order reaction with half-reduction period 5.6 h; disproportionation of Am(4) is not observed. Formal redox potential values for Am4/Am3 pair in 0.3-2.0 mol/l phosphoric acid solutions in acetonitrile (1.31-1.10 V relatively mercury-sulphate electrode) and in solutions containing 0.5 mol/l H3PO4 and to 20% H2O are measured. Possibility of americium coulomb determination using Amsup((6))/Amsup((3)) pair is investigated