Radiochemical study of the kinetics of crystal growth in gels

A kinetic study was performed on nucleation and growth of crystals containing radioactive ions in gelatin and agar gels. The investigated crystals were: (CoHPO4)-Co-60, (CoS)-Co-60, Co-60(OH)(2), Co-60(SCN)(2), Tl-204(OH)(3) and Tl-204[(C2H5)(2)NCS2](3). The study shows that the crystal growth rate depends on the cation size and charge, the nature of anion as well as on the colloidal medium. The crystallisation process in the gel has two distinctive steps: diffusion of reactant ions in the gel followed by a chemical reaction which leads to nucleation of the crystal. Both steps are described quantitatively.