PHOSPHATE COMPOSITION OF PRECIPITATES FROM URINE-LIKE LIQUORS

The composition of the solid phases precipitating from urine-like liqu ors has been determined at 37 degrees C over the pH range between 6 an d 8 for solutions with varying amounts of magnesium, citrate, oxalate and ammonium ions. At pH less than or equal to 7 hydroxyapatite appear ed, either alone or, depending on the magnesium ion concentration, in a mixture with brushite. Struvite and calcium phosphates precipitated at pH greater than or equal to 7.5. No other phosphate solids were obs erved to precipitate from these urine-like liquors under physiological conditions. No influence on the nature of the solid phase was exerted by citrate, oxalate or ammonium ions. The variation of solid phase co mposition caused by changing solution composition is ascribed to kinet ic rather than thermodynamic factors.