Melting Points of Mixtures of Cetyl Caprate with Lauryl Myristate

Abstract

THE work of Oldham and Ubbelohde¹ suggested that the melting point of mixtures of dipolar compounds may be much lower than predicted by the Le Chatelier–Schröder (or Hildebrand) equation² if one uses components which are able to crystallize in a composite lattice but are sufficiently different in chain-length to lead to the formation of a defective lattice. The formation of lattice flaws is made possible by the arrangement of the dipoles of all components in continuous dipole sheets throughout the crystal, Oldham and Ubbelohde proved the usefulness of this picture for mixtures of various long-chain ketones. In order to test the applicability of this hypothesis to mixtures of esters, a series of mixtures was prepared from two esters (cetyl caprate and lauryl myristate) which happened to be available in better than 95 per cent purity. The overall chain-length of these esters is identical; but their arrangement along a dipole sheet would lead to a high concentration of lattice flaws (Fig. 1). Judging by Oldham's work, the relative concentration of lattice flaws in either configuration should be sufficient to promise a substantial reduction in lattice stability, that is, in melting point.