EFFECTS OF SILVER, ALUMINUM, AND CHROME IONS ON THE POLYMORPHIC FORMATION OF CALCIUM-CARBONATE UNDER CONDITIONS OF DOUBLE DIFFUSION

The effects of Ag+, Al3+, and Cr3+ ions on calcium carbonate polymorph s were investigated using a double diffusion technique. The experiment al results, analyzed by the equivalency rule, were as follows: (i) Ag, Al3+, and Cr3+ ions promoted the formation of aragonite; (ii) in the presence of Ag+ ions, Ag2CO3 crystals acted as a nucleus for the epit axial growth of aragonite; (iii) Al3+ and Cr3+ ions reduced the growth rate of the metastable phase (aragonite), which was formed at the ini tial stage of CaCO3 crystallization. Due to their adsorption onto grow th sites, the supersaturation remained at a high level in this system. Aragonite was therefore able to be the dominant phase. (C) 1998 Acade mic Press.