HYDROTHERMAL CHEMISTRY OF SEAWATER FROM 25 degree TO 350 degree C.

Progressive heating of seawater to 350 degree C causes it to become increasingly acid and depleted in Ca, Mg, and SO//4, because anhydrite and a previously undescribed magnesium oxysulfate are precipitated. The pH at experimental conditions drops to 3. 3, while the buffer capacity of seawater increases from 0. 24 meq/pH at 25 degree C to 54 meq/pH at 350 degree C. Theoretical solubilities of brucite, anhydrite, magnesite, dolomite, and calcite were compared to ion-activity products. Comparison of solution composition with theoretical solubilities indicates that carbonate minerals were supersaturated with increasing temperature.