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

Abstract

The present paper reports a study on the relation between the deactivation temperatures of five nucleating agents for supercooled NaCH₃COO·3H₂O and crystallographic matching on a point of view of the arrangement of Na atoms. The deactivation temperatures of Na₂SO₄, NaCl, NaBr, Na₂HPO₄·2H₂O, and Na₃PO₄·0.5H₂O were 333, 335, 339, 348, and 360 K, respectively. The crystal structural correlation between NaCH₃COO·3H₂O 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 Å. 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.