Jacques Schwartzentruber

Dissolution of quartz into dilute alkaline solutions at 90°C: A kinetic study

Abstract The rate of dissolution of Fontainebleau sand (pure quartz) into sodium hydroxide solutions (from 0.001 M to 0.5 M) has been determined at 90°C in well-stirred vessels. Dissolution leads to an equilibrium state, controlled by the solubility of quartz in pure water as undissociated silicic acid H4SiO4. As long as the initial molality of sodium hydroxide does not exceed 0.02 mol · kg−1, the dissolution leads only to the formation of the three monomeric species H4SiO4, H3SiO4− and H2SiO42−, while polymers appear in the silica-rich solutions obtained in more alkaline media. The rate of dissolution can be represented by an adaptation of Stobers model to alkaline solutions; the basic assumption is that the quartz surface is partially covered by a layer of adsorbed silicate ions, which represent an intermediate species between solid and dissolved silica.

Representation of the vaporliquid equilibrium of the ternary system carbon dioxide propane methanol and its binaries with a cubic equation of state : a new mixing rule

Abstract Erroneous liquid phase splitting is often predicted when correlating the vapor-liquid equilibrium of alcohol-alkane systems with a cubic equation of state. It is shown that even the local-composition mixing rules are not sufficiently flexible for an accurate representation of the propane-methanol system, and a new empirical three-parameter mixing rule is introduced. The ternary system carbon-dioxide - propane - methanol is well-predicted from the binary data.

Modeling of multiphase liquid equilibria for multicomponent mixtures

Abstract A computational procedure to correlate multicomponent, multiphase liquid equilibria in terms of excess Gibbs energy models is described. This includes an efficient hybrid algorithm for solving the multiphase liquid equilibria flash problem which is an extension of the approach proposed by Ammar and Renon to perform vapor-liquid flash calculations. The algorithms presented in this work for the calculation of multiphase liquid equilibria, the themodynamic stability test based on the tangent plan criterion, as described by Michelsen, and the methods for estimation of interaction parameters of the NRTL, UNIQUAC, and extended UNIQUAC models, were tested on the representation of experimental two- and three-liquid phase equilibrium data of ternary and quaternary mixtures. Agreement between calculated and measured equilibrium data was excellent for most systems studied.

Equations of state: how to reconcile flexible mixing rules, the virial coefficient constraint and the “michelsen-Kistenmacher syndrome” for multicomponent systems

Schwartzentruber J. and Renon H., 1991. Equations of state: how to reconcile flexible mixing rules, the virial coefficient constraint and the “Michelsen-Kistenmacher syndrome” for multicomponent systems. Fluid Phase Equilibria, 677: 99-110. Non-quadratic mixing rules in the attractive parameter of a cubic equation of state are very effective for the correlation of phase behaviour of strongly non-ideal systems. However, these mixing rules are not consistent with the second virial coefficient being a quadratic function of mole fractions. Recently, Michelsen and Kistenmacher pointed out other drawbacks of some of these mixing rules. In this paper, we present a new formulation of such mixing rules which avoids these problems, and a simple form of the density-dependency of the mixing rules which keeps the cubic form of the equation of state, while ensuring consistency with the second virial constraint.

New determinations of high pressure vapor-liquid equilibria in binary systems containing n-propylbenzene with nitrogen or carbon dioxide consistent with the Prausnitz-Keeler test

The test of Prausnitz and Keeler consists of plots, or linear regression derived from the equality of fugacities of the heavy component in the liquid and vapor phases, giving the cross second and third virial coefficients. Its application resulted in improvement of the capillary sampling static method of measurements of P,x,y,T data and showed the consistency of new data for the systems of propylbenzene with CO2 and N2 obtained by five different experimental methods, including four static methods with three different sampling techniques, and one variable volume cell and one dynamic method.

Protein precipitation by caprylic acid: Equilibrium composition data

The precipitation equilibria of hen egg‐white lysozyme and bovine serum albumin from aqueous solutions by caprylic acid were studied. A thermodynamic equilibrium was obtained, and the compositions of both the precipitate and the aqueous phases were measured to establish phase diagrams for both systems. The precipitate was not pure protein, but also contained large amounts of water and caprylic acid. At constant initial pH and ionic strength, the composition of both phases depended only on the overall composition of the system. This suggests that protein precipitation by fatty acids should be pictured as liquid–liquid rather than solid–liquid equilibria. The precipitated proteins retained high biological activity.