Changes in calcium oxalate crystal, morphology as a function of concentration.

Calcium oxalate solutions in a wide range of concentrations were prepared and allowed to precipitate to determine how alterations in the calcium-to-oxalate ratio and the relative calcium oxalate supersaturation affected crystal morphology. The crystals were examined optically and with X-ray diffraction and their morphology was found to be closely related to relative supersaturation. Calcium oxalate monohydrate was the predominant species at all concentrations in which calcium oxalate precipitate was found. Calcium oxalate dihydrate was found only at high concentrations of both calcium and oxalate and underwent transformation to the monohydrate within 24 hr. Calcium oxalate trihydrate was not detected in any sample.