Fragments of the phase diagrams of ethylene glycol systems in the region of low second component concentrations

Fragments of the phase diagrams of the ethylene glycol (EG)-tert-butanol (t-BuOH) and EG-tet-ramethylurea (TMU) binary systems were studied by differential scanning calorimetry in the region rich in EG up to a ～40 mol % concentration of the second component. Liquid-phase stratification occurred at ～10–37 mol % t-BuOH and ～8–25 mol % TMU at ?37°C in the EG-t-BuOH system and at ?22°C in the EG-TMU system. The occurrence of liquid stratification was substantiated by visual observations of the solutions of the concentrations specified at a constant temperature of ?20°C. A comparison of the results obtained with the data on light scattering in the systems under study over the temperature range 25–50°C lends support to the hypothesis of the subcritical state of solutions of nonelectrolytes in solvents with a 3D network of hydrogen bonds at low solute concentrations.