Phosphate Composition of Precipitates from Urine‐like Liquors

The composition of the solid phases precipitating from urine‐like liquors has been determined at 37°C over the pH range between 6 and 8 for solutions with varying amounts of magnesium, citrate, oxalate and ammonium ions. At pH ⩽7 hydroxyapatite appeared, either alone or, depending on the magnesium ion concentration, in a mixture with brushite. Stravite and calcium phosphates precipitated at pH ⩾ 7.5. No other phosphate solids were observed 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 composition caused by changing solution composition is ascribed to kinetic rather than thermodynamic factors.