A STUDY OF THE RELATIONSHIP BETWEEN THE CHEMICAL-STRUCTURE OF SOME CARBOXYLIC-ACIDS AND THEIR CAPACITY TO INHIBIT THE CRYSTAL-GROWTH OF CALCIUM-FLUORIDE

The influence of oxalic acid, malonic acid, malic acid, tartaric acid, succinic acid and glycolic acid on the growth of calcium fluoride has been studied and interpreted in terms of Langmuir-type adsorption isotherms. Oxalic acid was the most active inhibitor of calcium fluoride growth, followed by tartaric, malic and malonic acids. Succinic acid caused a very slight effect and monocarboxylic acids caused no inhibitory effects under the conditions studied. An attempt to relate the chemical structure of the studied carboxylic acids with their inhibitory capacity using molecular models and MNDO calculation has been described. The presence of a sequence constituted by a carboxylic group and an hydroxy group in the alpha position, in addition to another carboxylic group demonstrated a special efficacy to inhibit crystal growth of calcium fluoride crystals due to structural features. Interactions between inhibitors and the crystal surface were found to be mainly electrostatic in nature.