One- and two-phase isochoric heat capacities and saturated densities of 2-propanol in the critical and supercritical regions

Abstract

One- (CV1) and two-phase (CV2) liquid + vapor equilibrium isochoric heat capacities, densities (ρS), and phase-transition temperatures (TS) of 2-propanol were measured in the critical region. Measurements were made in the immediate vicinity of the liquid–gas phase transition and critical point in order to accurately determine the locus of phase-transition properties (TS, ρS, CV1, and CV2). Additional measurements were made over an extended temperature range from (317 to 525) K for 9 liquid and 3 vapor isochores between (234 and 697) kg⋅m−3 at pressure up to 6.5 MPa. The measurements were performed using a high-temperature, high-pressure, nearly constant-volume adiabatic piezo-calorimeter. The standard uncertainty of the density, temperature, and isochoric heat capacity (CV) measurements is estimated to be 0.1%, 0.02 K, and 1.5%, respectively. The measured one- (CV1) and two-phase (CV2) isochoric heat capacities along the critical isochore and the saturated liquid (ρS') and vapor (ρS'') densities near the critical point were used to derive theoretically meaningful asymptotic critical amplitudes (A0± and B0) and related amplitudes for other properties (Γ0+,D0,ξ0) and their universal relations, A0+/A0-, A0+Γ0+B02, αA0+Γ0+B0-2, D0Γ0+B0δ-1, ξ0αA0+vC1/3 and the asymmetric parameters a3 and b2 of the coexistence curve singular diameter. Experimental two-phase heat capacities CV2 as a function of specific volume V , along various isotherms, were used to calculate second temperature derivatives of vapor pressure d2PSdT2 and chemical potential d2μdT2 and to estimate the value of the Yang-Yang anomaly strength parameter Rμ for 2-propanol. The relative contributions of the vapor pressure, CVP=VCTd2PSdT2, and the chemical potential, CVμ=-Td2μdT2, to the measured total two-phase CV2 were estimated.