Phases of variable composition in crystallization of cesium phosphomolybdate

Abstract

Cesium phosphomolybdate crystallizes from nitric acid solutions in the form of compounds with variable composition CsxH3−xPO4 · 12MoO3 · nH2O (x = 0.8−3.0). Irrespective of the x value, the crystals have invariable cubic body-centered lattice differing in the structure from the known ammonium salt. This cesium compound at x = 0.8−2.8 is very poorly soluble in acidic solutions: less than 0.2 mg Cs per liter. When cesium and ammonium ions are simultaneously present in the solution, crystallization results in the formation of a solid solution of cesium in ammonium phosphomolybdate, of ammonium in cesium phosphomolybdate, or of a mixture of these phases, depending on the conditions.