Precipitation and Hydrolysis of Thorium(IV) in Aqueous Solution. III. The Composition of the Precipitates in the System Thorium Nitrate - Potassium Phthalate

Precipitation from water solutions of thorium nitrate and potassium phthalate was investigated for a broad range of concentrations of both precipitation components. The influence of pH and of time on the formation of various precipitates was studied, the composition and characteristics of the precipitates being determined by chemical analysis, and IR and NMR spectra. The following precipitates were characterized: Th(OH).:1 without water of crystallization; Th (Phthalateh without water of crystallization; Thorium hydroxide-phthalate polymer with unknown formula. An empirical formula was derived, which shows the conditions for precipitation of thorium hydroxide in the presence of potassium phthalate. In the soluble mixed hydroxo-phthalato thorium complex, two OH- ions are bound per one thorium