Aziz I. Abdulagatov

Vapor-pressure for the pure fluids from calorimetric measurements near the critical point

Abstract We report the values of second temperature derivatives of the vapor-pressure curve (d2PS/dT2) and chemical potential (d2μ/dT2) for pure fluids derived from precise two-phase isochoric heat capacity measurements over a wide temperature range including the critical region. The values of (d2PS/dT2) derived from CV2 measurements were compared with the values calculated from direct differentiation of the vapor-pressure equation from the literature. The derived (d2PS/dT2) data has been used to develop a scaling-type vapor-pressure equation in the critical region. A description of the vapor-pressure calculation procedure from CV2 measurements is given. The values of the critical pressure PC and slope of the vapor-pressure curve (dPS/dT)C at the critical point were calculated by using calorimetric measurements. The asymptotic behavior of the second temperature derivatives of the vapor-pressure curve (d2PS/dT2) and chemical potential (d2μ/dT2) near the critical point are discussed. The strength of the Yang–Yang anomaly, Rμ, defined by Fisher as Rμ=Aμ/(Aμ+AP), where Aμ and AP are the amplitudes of the singularity of −T(d2μ/dT2)≈Aμt−α and TVC(d2PS/dT2)≈APt−α was estimated from derived results.

Extrema of isochoric heat capacity of water and carbon dioxide

The experimental and predicted loci extrema behavior of the isochoric heat capacity Cv was examined for water and carbon dioxide along the subcritical and supercritical isotherms and along the liquid and vapor isochores. The studies were based on a nonanalytical Helmholtz energy-volume-temperature equation (AVT, fundamental equation of state), the IAPWS-95 formulation for water, and scaling-type crossover equations of state (CREOS). The measured isochoric heat capacity data for these fluids near the critical point were analyzed to study the behavior of loci of Cv maxima and to compare these with predictions by the equations of state. A CREOS was applied to study the behavior of the isochoric heat capacity maxima in the immediate vicinity of the critical point. Good agreement with the CREOS prediction and experimental isothermal Cv maxima loci was observed near the critical point. The basic characteristic points on the Cv extrema loci curves in the P-T and 𝜌-T planes were determined on the basis of detailed analysis of the experimental and prediction of Cv extrema loci behavior. Qualitative explanations are given for the nature of isochoric and isothermal Cv maxima-minima curves. The role of Cv extrema loci behavior in developing high-accuracy equations of state in the supercritical region and in the study of supercritical phase-transition phenomena are discussed.

Crossover Equation of State and Microstructural Properties of Infinitely Dilute Solutions Near the Critical Point of a Pure Solvent

Microstructural (correlation integrals, cluster size) and related thermodynamic (partial molar volume, Krichevskii parameter) properties of infinitely dilute solutions near the critical point of a pure solvent are studied in terms of nonclassical (crossover) equations of state. The Krichevskii parameter was evaluated for a number of binary solutions by analyzing the initial slopes of the critical lines and the properties of a pure solvent. Qualitative explanation is offered for the physicochemical mechanism of the anomalously high solubility of slightly volatile substances in a supercritical solvent based on microstructural and thermodynamic characteristics of a supercritical fluid mixture.

Critical properties of aqueous solutions. P. II

Results from a detailed study are presented in which we analyzed the shape of critical lines of binary aqueous solutions like H2O + common salt and H2O + hydrocarbon. We also present the results from a comparative analysis of data on the critical parameters of such solutions reported in the literature. The critical lines of the solutions are analyzed in different projections. Accuracy, reliability, and consistency of the data considered are estimated, and recommendations on using them for scientific and practical purposes are given.

Critical properties of aqueous solutions. Part 1: Experimental data

All data available in the literature on the critical properties of binary aqueous solutions like H2O + common salt, H2O + hydrocarbon, H2O + alcohol, H2O + gas, and others are gathered. Methods for determining them are presented together with errors and concentration measurement intervals for each source of data. The format in which the data are presented will allow the readers to quickly find the necessary information on the critical properties of aqueous solutions from the original sources and use them for solving scientific and engineering tasks. Certain general features of the critical lines and phase diagrams of aqueous solutions with volatile and nonvolatile components are discussed.

Critical properties of aqueous solutions. Part 3

We present the results from a detailed study analyzing the shape of the critical lines of binary aqueous solutions (H2O + alcohol, H2O + gas, and H2O + NH3) in different projections. We also present a comparative analysis of data on the critical parameters of solutions from different sources, as well as an estimation of how accurate, reliable, and consistent these data are.