Precipitation and Hydrolysis of Thorium(IV) in Aqueous Solution. II. Influence of pH and Neutral Electrolytes upon the Precipi tation in the System Thorium Nitrate - Potassium Phthalate

Abstract

The influence of the pH and other neutral electrolytes upon the precipitation and hydrolysis of thorium(IV) in aqueous solutions of thorium nitrate and potassium phthalate was investigated. A three-dimensional concentration tyndallogram in which turbidity has been plotted against the concentration of potassium phthalate and the pH, at constant concentration of Th(IV) 1.25 X 10-3M, shows various precipitation and dissolution regions of th e system. The following co ncentration regions were marked and discussed: the concentration region where sudden precipitation of thorium hydroxide occurs, the region of thorium hydroxide stable sols, the region of thorium phthalate sols, the region of unstable systems in which crystals appear after a few days\u27 aging and the region of stable clear solution at rathe r high pH values. The effect of neutral electrolytes upon the precipitation in the regio n of stable clear solution was investigated. It was d etermined that neutral electrolytes influence to a great extent the prec ipitation at the boundary of thorium phthalate precipitate (pH= 5)