THE PHYSICAL STATES OF ANHYDROUS SODIUM SOAPS

Abstract

Density measurements and differential cooling curves have been carried out on sodium stearate and sodium oleate over a range of temperatures. For sodium stearate, the genotypical or unidimensional melting point at 70 °C. found by Thiessen et al. has been corroborated. A large transition has been noted at about 100 °C. and it is suggested that this phase transition is due to a melting in a second dimension at right angles to the molecular axis. A further large transition has been found at 125° to 130 °C. leading to a plastic state in the soap, and it is suggested that this transition point denotes the essential completion of bidimensional melting of the lattice. No further considerable phase change was found up to about 200 °C., when disruption of the polar bonds probably occurs to effect complete disruption of the lattice to the liquid crystalline state. Only the latter transition point was found for sodium oleate at about 135 °C.