Equilibria of Sodium Salicylate-Water System

1) Solubility of sodium salicylate was measured by an analytical method and conditions for crystallization were examined by thermal analysis.2) Viscosity of saturated solution and dissociation vapor pressure of hydrates were measured, and transition point of the hydrates was determined from the break in the solubility curve, viscosity-temperature curve, and vapor pressure-temperature curve.3) Mutual solubility of the sodium salicylate-sodium hydroxide-water system at 0° was measured. It was thereby found that the compounds in the lower liquid phase were hexahydrate and anhydrate, the anhydrate being present when the concentration of sodium hydroxide in the solution is above 23% by weight and the hexahydrate at below this concentration. The anhydrate was found to be present in a metastable state at the concentration of sodium hydroxide below 23% by weight.