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

Highlights: • Phase transitions and critical phenomena for 2-propanol were measured with a calorimeter. • Caloric property behavior was measured from (317 to 525) K at pressures up to 6.5 MPa. • Near the critical density of 266.30 kg · m⁻³ we examine the Yang-Yang critical anomaly. • The influence of chemical structure on the Yang-Yang critical anomaly was examined. -- Abstract: One- ($C_{\text{V1}}$) and two-phase ($C_{\text{V2}}$) liquid + vapor equilibrium isochoric heat capacities, densities (${\rho }_{\text{S}}$), and phase-transition temperatures ($T_{\text{S}}$) 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 ($T_{\text{S}}$, ${\rho }_{\text{S}}$, $C_{\text{V1}}$, and $C_{\text{V2}}$). 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 ($C_{\text{V}}$) measurements is estimated to be 0.1%, 0.02 K, and 1.5%, respectively. The measured one- ($C_{\text{V1}}$) and two-phase ($C_{\text{V2}}$) isochoric heat capacities along the critical isochore and the saturated liquid (${\rho }_{\text{S}}^{\text{'}}$) and vapor (${\rho }_{\text{S}}^{\text{''}}$) densities near the critical point were used to derive theoretically meaningful asymptotic critical amplitudes ($A_{\text{0}}^{\pm }$ and $B_{\text{0}}$) and related amplitudes for other properties (${\Gamma }_{\text{0}}^{+},D_{\text{0}},{\xi }_0$) and their universal relations, $A_{\text{0}}^{+}$/$A_{\text{0}}^{-}$, $A_{\text{0}}^{+}{\Gamma }_{\text{0}}^{+}{B}_{\text{0}}^2$, $\alpha A_{\text{0}}^{+}{\Gamma }_{\text{0}}^{+}{B}_{\text{0}}^{-2}$, $D_0{\Gamma }_0^{+}{B}_0^{\delta -1}$, ${\xi }_0{\left(\frac{\alpha A_0^{+}}{v_C}\right)}^{1/3}$ and the asymmetric parameters $a_3$ and $b_2$ of the coexistence curve singular diameter. Experimental two-phase heat capacities $C_{\text{V2}}$ as a function of specific volume V , along various isotherms, were used to calculate second temperature derivatives of vapor pressure $\frac{{\text{d}}^2{P}_{\text{S}}}{\text{d}{T}^2}$ and chemical potential $\frac{{\text{d}}^{\text{2}}\mu }{\text{d}{T}^2}$ and to estimate the value of the Yang-Yang anomaly strength parameter $R_{\mu }$ for 2-propanol. The relative contributions of the vapor pressure, $C_{\text{VP}}=V_{\text{C}}T\frac{{\text{d}}^2{P}_{\text{S}}}{\text{d}{T}^2}$, and the chemical potential, $C_{\text{V}\mu }=-T\frac{{\text{d}}^{\text{2}}\mu }{\text{d}{T}^2}$, to the measured total two-phase $C_{\text{V2}}$ were estimated.