Growth of calcium oxalate crystals. I. A model for urinary stone growth.

The kinetics of the crystal growth of calcium oxalate monohydrate has been studied using the technique of seeded crystal growth from stable supersaturated solution. The rate law takes the form minus dc/dt equals kN-2 in which the rate of loss of lattice ion from solution is proportional to the square of the supersaturation. It is proposed that the incorporation of lattice ions into the crystal is governed by a bimolecular surface-controlled reaction step. The rate is independent of the hydrodynamics of the system but is proportional to the solid to solution ratio in the supersaturated solution. The specific rate constant, k (M-minus-1 min-minus-1 [mg/dl]minus-1), is nearly independent of the solid to solution ratio, however. The rate of crystal growth was found not to vary with the calcium to oxalate molar ratio in the range 1.5 to 0.75, although the rate did increase at both higher and lower ratios. The method was found to be simple, rapid, and reproducible and lends itself to the quantitative study of inhibitors of crystal growth.