INFLUENCE OF PRESSURE ON EXCESS THERMODYNAMIC CHARACTERISTICS OF WATER-DIMETHYLSULFOXIDE MIXTURES

Excess molar volumes V-m(E), changes in the excess molar thermodynamic characteristics such as Gibbs energy Delta(Po -> P)G(m)(E), entropy Delta S-Po -> P(m)E, and enthalpy Delta H-Po -> P(m)E of water - dimethylsulfoxide mixture were calculated in the temperature range of 298.15-323.15 K and pressure range of 0.1-100 MPa. It was revealed that values of V-m(E) are negative for all mixture compositions and for all range of pressure and temperature. Composition dependences of Delta(Po -> P)G(m)(E), Delta S-Po -> P(m)E and Delta H-Po -> P(m)E are characterized by the presence of extremes. The endothermic maximum is observed on the composition dependence of Delta H-Po -> P(m)E in the range of small amounts of dimethylsulfoxide. Entropy change at these DMSO concentrations shows the lowering pressure effect in the process of system ordering.