The solubility of disodium terephthalate in aqueous sodium hydroxide and in aqueous sodium hydroxide-ethylene glycol mixtures was determined experimentally by temperature analysis, gravimetry and titration. The experimental results were compared with existing literature data and the phase diagrams were determined from -25 to 70 °C. The solubility of disodium terephthalate has no considerable dependence on temperature. The freezing points of disodium terephthalate solutions vary with composition like any other solution. The solubility and freezing points decrease with increasing concentrations of ethylene glycol. Disodium terephthalate is salted out by the addition of sodium hydroxide.