engleski

Precipitation and solubility of calcium hidrogen urate hexahidrate

The composition, conditions of precipitation and solubility of calcium urate are of considerate interest becouse of their possible occurence in renal calculi. However solubility data are not yet available and there is moreover considerable confusion in the literatue concerning the exact chemical composition of such a compound. In this work calcium hydrogen urate hexahydrate, (Ca(C_5H_3O_3N_4)_2x6H_2O ; Ca(HU)_2x6H_2O) was prepared by dissolvong anhydrous uric acid in aqueous solutions of calcium hydroxide and xydrochloric acid. Pure crystals of the compound, as characterized by X-ray diffraction powder patterns, chemical and thermogravimetric analysis, were obtained in the range of pH 7 less-than or equal to pH less-than or equal to 10 and uric acid concentration 10^-2 greater-than or equal to H_2U greater than or equal to 10^-3 at calcium/uric molar rations 1.1 - 1.5. Exact conditions of preparation of Ca(HU)_2x6H_2O and data on its solubility in aqeous solutions are given. The anhidrous form. CaC_5H_3O_3N_4, has also been prepared and characterized.

urate; preparation; X-ray diffraction

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