Investigation of the ( T,p,x,) surface of phase separation of { xH 2O + (1 − x) NC(CH 3) CHCHCHC(CH 3)} in the vicinity of the line of lower critical points of dissolution

Abstract

The (T,p,x,) surface of the (liquid + liquid) phase equilibrium has been investigated in the vicinity of the line of lower critical points of dissolution of {xH2O + (1 − x) NC(CH3)CHCHCHC(CH3)}. Measurements were carried out in a high-pressure optical cell in the pressure range from 0.1 MPa to 230 MPa. The behaviour of critical exponents for (T, x) and (p, x) diagrams of phase equilibrium, βpβT, respectively, has been studied along the critical line and at the double critical point (DCP) with coordinates pD = 110 MPa and TD = 312.25 K. It is shown tha the exponent βp retains its value along the line of critical points, including the DCP, while βT increases anomalously with approach to the DCP. In this case βT(pc = pD) ≈ 2 · βT(pc = 0.1 MPa).