Abstract:

The exptl. conditions to maintain metastability in a soln. of Ca oxalate during 15 min were defined. Seed crystals of uric acid and Na urate were added, and the decrease in Ca ion concn. was measured by a Ca-selective electrode. Na urate crystals caused a decrease of ∼14%, while uric acid seeds were inactive. The growth of Ca oxalate on Na urate surface was confirmed by x-ray emission anal. When glutamic acid was added at 4-5 ppm concn. to the metastable soln. contg. uric acid seeds, a ∼28% Ca-concn. decrease was obsd. The pptn. of Ca oxalate on uric acid was confirmed by x-ray emission anal. A structural fit at an at. level between 2 solids, which is a necessary condition for epitaxy, is not sufficient for growth to occur. An addnl. factor, namely attraction at an ionic or mol. level, is also needed. It may be furnished by a mediating agent compatible with both solids. [on SciFinder(R)]