THE INFLUENCE OF CRYSTAL MORPHOLOGY ON THE KINETICS OF GROWTH OF CALCIUM-OXALATE MONOHYDRATE

The growth of several calcium oxalate monohydrate seeds in the presenc e and absence of additives (phytate, EDTA and citrate) has been follow ed by potentiometry measurements. Growth rates have been calculated fr om precipitate curves by a cubic spline method and represented in loga rithmic plots versus supersaturation. Crystal growth kinetics were fou nd to be dependent on crystal morphology, crystal perfection and degre e of aggregation. Some seeds were dissolving in supersaturated solutio ns. Other seeds showed an initial growth phase of high-order kinetics. The effect of the additives was also different on each seed. Three al ternative mechanisms for calcium oxalate crystal growth are proposed.