Preparation and characterization of uniform particles of uric acid and its salts

Uric acid, the major component in many kinds of kidney stones, as well as its sodium, ammonium, calcium, and barium salts were successfully prepared as uniform dispersions by precipitation in basic aqueous solutions. The effects of the reactant concentrations, pH, and the stabilizers were evaluated in detail. Except for the platelets of the pure acid, all prepared compounds appeared as needles or their aggregates. The electron micrographs showed that kidney stones consisted of such aggregates although less regular in size and morphology. All prepared urate salts had a 1:1 cation/uric acid ratio, regardless of the valence of the cation. The electrokinetic measurements showed all these particles to have negative ζ-potentials over the pH range 3-9. The precipitated salt particles were chemically and morphologically unstable at low pH values by decomposing into ill-defined aggregates of the pure uric acid.