Thorium Molybdate, Th(MoO₄)₂

Thorium Molybdate, Th(MoO₄)₂, is obtained by fusing partly dehydrated thorium chloride with excess of anhydrous sodium molybdate. It yields tetragonal crystals, with axial ratio

a:c = 1:0.73565,

and density 4.92 at 7.5° C. The crystals exhibit mutual miscibility in the solid state with cerous molybdate.

A series of complex thoromolybdates, derived from an acid of the type H₈[Th(Mo₂O₇)₆], has been prepared. The normal ammonium salt, (NH₄)₈[Th(Mo₂O₇)₆].8H₂O, forms as a white precipitate on the addition of thorium sulphate to a concentrated solution of ammonium paramolybdate. The thoromolybdate dissolves in nitric acid, and the solution is almost completely precipitated by silver nitrate. The solution in nitric or hydrochloric acid, when treated with a concentrated solution of an ammonium salt, yields ammonium hydrogen thoromolybdate, (NH₄)₆H₂[Th(Mo₂O₇)₆].11H₂O. The corresponding sodium salts, Na₈[Th(Mo₂O₇)₆].15H₂O and Na₆H₂[Th(Mo₂O₇)₆].17H₂O, are similarly prepared. Silver thoromolybdate, Ag₈[Th(Mo₂O₇)₆], is a white powder. The solutions of the ammonium and sodium salts also yield precipitates on the addition of magnesium or zinc salts.