ASPECT ON INTERFACIAL CHARACTERISTICS OF CARBONATE MINERALS IN WATER.

When a carbonate mineral comes in contact with water, the process through which equilibrium between solid, liquid and air is established is grouped into two types: (1) the solid-liquid system monotonously reaches its equilibrated state with air in a short time; (2) the solid-liquid system approaches the apparent system closed to air, after which it reaches its equilibrium state with air after a lengthy period. Manganese carbonate and lead carbonate belong to type (1), and calcium carbonate, barium carbonate and strontium carbonate belong to type (2). The difference between type (1) and type (2) is caused by the magnitude of the solubility product. The pH values at zero H** plus and OH** minus demand of the carbonate minerals were measured by potentiometric titration. The variation of the pH values with time and variation of the isoelectric points reported by many reseachers are related to the variation of the IEP(aq) values calculated by chemical thermodynamics under particular conditions.