LINEAR GROWTH-RATES OF CALCIUM-SULFATE DIHYDRATE CRYSTALS IN THE PRESENCE OF ADDITIVES

The linear growth rates of CaSO4·2H2O crystals in the presence of carboxylic and phosphonic acid derivatives have been examined by optical microscopy. The crystals formed were of uniform shape and size. Application of Nielsen's chronomal (dimensionless time parameter) analysis demonstrated that growth follows second-order (in supersaturation) kinetics indicating a reactioncontrolled mechanism, polynuclear layer" growth. Crystals grown in the presence of additives exhibited habit modifications due primarily to inhibition of normal growth on the 111 faces of the CaSO4·2H2O crystals. Habit modification is explained on the basis of geometric factors relating the molecular structure of the additive to the crystal structure of gypsum. © 1979."