A Crystallographic Study on the Deactivation Temperature of Crystal Nucleating Agents for Supercooled Sodium Acetate Trihydrate

The present paper reports a study on the relation between the deactivation temperatures of five nucleating agents for supercooled NaCH3COO.3H(2)O and crystallographic matching on a point of view of the arrangement of Na atoms. The deactivation temperatures of Na2SO4, NaCl, NaBr, Na2HPO4 center dot 2H(2)O, and Na3PO4 center dot 0.5H(2)O were 333, 335, 339, 348, and 360 K, respectively. The crystal structural correlation between NaCH3COO center dot 3H(2)O and five nucleating agents was studied from the point of view of the arrangement of Na atoms in a crystal face slice. Periodic matching of a pair of Na atoms was observed in the area of 200-400 square angstrom. The degrees of matching, defined as a reciprocal of the number of unit cells which were contained in a parallelogram with four matching points, of above five nucleating agents were 1.0, 1.9, 5.0, 20, and 25%, respectively. A positive correlation between the deactivation temperatures and the crystallographic matching was found.