The (T, p, x) surface of phase separation of [(1 - x)H2O + x(CH3){CH3(CH2)4}2PO] in the vicinity of the line of the lower critical solution temperatures at pressures up to 230 MPa

Abstract

The (T, p, x) surface of (liquid + liquid) phase equilibrium has been investigated in the vicinity of the line of lower critical solution points of [(1 - x)H2O + x (CH3){CH3(CH2)4}2PO]. Measurements were carried out in a high-pressure optical chamber at pressures p in the range from 0.1 MPa to 230 MPa. The behaviour of critical exponents for (p, x) and (T, x) phase-equilibrium diagrams: βT and βp, respectively, has been studied along the critical line and at the double critical point (DCP) with coordinates PD = 127 MPa and TD = 296.5 K. The exponent βp retains its value along the line of critical points, including the double critical point; βT increases anomalously with an approach to the DCP.