The mineralization inhibitory potential of urines: a constant composition approach.

A constant composition potentiostatic method was used to investigate the crystallization kinetics of calcium oxalate monohydrate with high precision and reproducibility in the presence of whole (centrifuged) and dialyzed urines. The solution supersaturation is maintained constant by the potentiometrically controlled addition of lattice ion solutions. The method allows the calculation of urine inhibitory potentials to be made with a precision (5 per cent) hitherto unattainable, and avoids the complications resulting from large changes in supersaturation implicit in more conventional seeded crystallization experiments. A method of urine storage is described whereby the inhibitory potentials remain constant for up to 7 weeks of sample storage.