Phase Diagram of the Ethylene Glycol–Dimethylsulfoxide System

Abstract

The phase diagram of ethylene glycol (EG)–dimethylsulfoxide (DMSO) system is studied in the temperature range of +25 to −140°C via differential scanning calorimetry. It is established that the EG–DMSO system is characterized by strong overcooling of the liquid phase, a glass transition at −125°C, and the formation of a compound with the composition of DMSO · 2EG. This composition has a melting temperature of −60°C, which is close to those of neighboring eutectics (−75 and −70°C). A drop in the baseline was observed in the temperature range of 8 to −5°C at DMSO concentrations of 5–50 mol %, indicating the existence of a phase separation area in the investigated system. The obtained data is compared to the literature data on the H₂O–DMSO phase diagram.