CRYSTAL GROWTH AND DISSOLUTION OF BARIUM SULFATE.

The kinetics of crystallization and dissolution of barium sulfate seed crystals were investigated conductimetrically. Growth is characterized by an initial surge caused by secondary nucleation, followed by a rate that is proportional to the square of the supersaturation. Studies were made using seed material of differing morphology; in all cases, the crystallization was surface controlled. A surface reaction also appears to be rate-determining for the corresponding dissolution process, but the overall rate constant is considerably greater than that for growth. Crystallization and dissolution were studied in the presence of potential phosphonate and polyphosphate scaling inhibitors; in some cases, both processes were markedly inhibited. The incorporation of the antiscalant into the developing crystals may pose problems in downhole application. (20 refs.)