The solubility of zirconium(IV) hydroxide in the presence of oxalic and malonic acids was measured for a wide ran.-le of pH values and organic acid solutions prepared by the oversaturation method. In near-neutral pH Solutions, the apparent Solubility increased with the concentration of the organic acid due to the formation of soluble carboxylate complexes. On the other hand, under acidic conditions, a precipitate of carboxylate salts was formed and the Solubility was controlled by the precipitate. The complex formation constants and Solubility products of zirconium oxalate and malonate were obtained by analysis of the solubility results.