KINETICS OF CALCIUM TARTRATE CRYSTAL-GROWTH FROM SUPERSATURATED SOLUTIONS

The kinetics of calcium tartrate crystal growth were studied by carryi ng out potentiometric measurements. The apparent equilibrium constant for calcium tartrate ion association has been evaluated for the experi mental conditions used and was found to be 581 mol-1 l. The dependence of the apparent order of reaction on the supersaturation has been fou nd. When using higher supersaturation, the order of reaction (n) found suggested a crystal growth mechanism controlled by surface nucleation (n > 2). When using lower supersaturation, the order of reaction sugg ested a mechanism controlled mainly by screw dislocation growth (n alm ost-equal-to 2). The inhibitory action of several organic and inorgani c species has been tested. Only a few metals ions such as Zn2- caused a measureable inhibition and this corresponds to growth by surface nuc leation.