POLAROMETRIC TITRATION OF THORIUM IN MONAZITE

<正> It is difficult to find a rapid and accurate method for the analysis of thorium in monazite. Through a thorough investigation on the properties of the elements in monazite and the characteristics of polarometric titration, it is possible to combine steps of decomposition and polarometric titration more properly. A dried sample is fused with potassium hydrogen bifluoride; by selecting a mixture of aluminium chloride, acetic acid and sodium acetate as the supporting electrolyte, thorium can be rapidly and accurately determined by polarometric titration using ammonium molybdate as reagent. The optimum conditions are as follows: applied voltage -0.75 V （versus S.C.E.）, composition of supporting electrolyte: 1.5 N AICI3, 7% CH3COOH and CH3COONa （pH=1.7）. The precision of the determination lies within 2%. It takes three hours to carry through the determination.