Chemical Potentials Of Components Research Articles

Computer simulation of chemical potentials of ternary hard-sphere fluid mixtures

A new version of the scaled particle Monte Carlo (SP-MC) computer simulation method is proposed. It is used to determine chemical potentials of components of ternary mixtures of additive hard-sphere fluids at several densities and compositions. The results are used to test the chemical potentials given by two literature equations of state (EOS). It has been found that the simulation and EOS’s results are in very good agreement with the new data in this work.

A model of oxygen-activity-dependent adsorption (desorption) to metal–oxide interfaces

Non-reactive metal–oxide interfaces are thermodynamically stable over an extended range of oxygen activity and temperature. It is supposed that, at each point of this range, the interface adopts a (slightly) different equilibrium structure and chemistry due to variations in the local composition of the interface by Gibbs' adsorption. The quality and quantity of adsorbed species at the interface, chemical bonding across the metal–oxide interface and related properties, such as adhesion for example, should then vary with the external parameters, temperature and chemical potential of the components.A physico-chemical continuum model is developed that applies point defect chemistry to transition metal–oxide interfaces. It predicts specific interfacial energies through Gibbs' adsorption isotherms as a function of component chemical potentials. Experimental results obtained for MgO–Cu interfaces are reviewed and compared with the model's results.

Disequilibrium processes along gradients in Earth’s gravitational field

Irreversible thermodynamics treat disequilibria in Earth’s open systems, gravitational fields, and gradients in temperature, pressure, and composition. Equilibrium studies on closed systems lack gradients and apply most closely to phase events in restricted volumes of the Earth. Liquid silicates are governed by rules of solution chemistry: solubilities of phases, chemical potentials of components, and kinetics of irreversible reactions. Magma bodies enter the crust physically by penetration of diapirs along zones of structural weakness, and passively, by chemical replacement of country rocks. Chemical mechanisms based on irreversible principles are Ortolevan reaction cells that rise in gravitational fields by cycling excess energies of liquefaction between endothermic dissolution at cell tops and exothermic precipitation at cell bases; released energies migrate upward in central liquid zones. Cells that halt within the crust produce passively emplaced plutonic intrusives; those that penetrate to the surface form volcanic fields genetically associated with intrusives below.

Relation Between Integral and Partial Properties of Ternary Solutions Along Different Composition Trajectories

The relations between partial and integral properties of ternary solutions along composition trajectories suggested by Kohler, Colinet and Jacob, and along an arbitrary path are derived. The chemical potentials of the components are related to the slope of integral free energy by expressions involving the binary compositions generated by the intersections of the composition trajectory with the sides of the ternary triangle. Only along the Kohler composition trajectory it is possible to derive the integral free energy from the variation of the chemical potential of a single component with composition or vice versa. Along all other paths the differential of the integral free energy is related to two chemical potentials. The Gibbs-Duhem integration proposed by Darken for the ternary system uses the Kohler isogram. The relative merits of different limits for integration are discussed.

Thermodynamic constraints along isograms in ternary systems: application to three-phase equilibria

Thermodynamic constraints on component chemical potentials in three-phase fields introduced by the various isograms suggested in the literature are derived for a ternary system containing compounds. When compositions of two compounds lie on an isogram, it is associated with specific characteristics which can be used to obtain further understanding of the interplay of thermodynamic factors that determine phase equilibria. When two compounds are shared by adjacent three-phase fields, the constraints are dictated by binary compositions generated by the intersection of a line passing through the shared compounds with the sides of the ternary triangle. Generalized expressions for an arbitrary line through the triangle are presented. These are consistent with special relations obtained along Kohler, Colinet and Jacob isograms. Five axioms are introduced and proved. They provide valuable tools for checking consistency of thermodynamic measurements and for deriving thermodynamic properties from phase diagrams.

Chemical potentials of components of the system CaO + P2O5 + FexO at 1673 K

Electromotive force (emf) measurements were conducted with a solid oxide galvanic cell of the type Mo/Mo + MoO2/ZrO2 (MgO)/Fe (s) + FexO (in slag)/Ag/Fe at 1673 K in order to obtain the activities of FexO in CaO + P2O5 + FexO ternary slags. By using the Gibbs-Duhem integration, the activities of P2O5 and CaO were also obtained.

A thermodynamic model for the phase behavior of salt-polymer aqueous two-phase systems

A statistical mechanical model for the component chemical potentials has been developed to predict the behavior of multiphase aqueous salt-polymer mixtures. The model includes the effect of polymer molecular mass on system phase behavior by means of scaling laws. The model parameters have been evaluated from binary and ternary isopiestic water activities and from solution volumetric data. Calculated phase diagrams for five different systems comprising three different polyethylene glycols and three different salts are shown. Model calculations show generally good agreement with experimental results.

Molecular Thermodynamics for Chemical Process Design

AbstractThermodynamic properties are essential for quantitative process design to produce chemical products. Caloric properties are required for heat balances, but these properties are usually available or estimated easily. More important—and often much more difficult to estimate—are the chemical potentials of components in mixtures; it is these potentials which determine phase equilibria, as required for separation operations, and chemical equilibria, as required for chemical reactors and for separation operations based on chemical reactions. Molecular thermodynamics is an engineering‐oriented science for calculating the desired chemical potentials from a minimum of experimental data. This applied science, based on classical and statistical thermodynamics, yields chemical potentials through models that are based on molecular physics and physical chemistry. Selected examples are cited to illustrate the applicability of molecular thermodynamics: group‐contribution methods for obtaining chemical potentials in highly nonideal mixtures as required for distillation‐column and process‐safety design; equation of state for precipitation of uniform‐sized crystals from supercritical fluids; molecular‐orbital calculations to guide process development for alternatives to environmentally dangerous chlorofluorohydrocarbons; molecular‐simulation calculations for separation of gas mixtures with porous adsorbents; equilibria in two‐phase aqueous systems for separation of protein mixtures; and, finally, extended polymer‐solution thermodynamics to guide synthesis of hydrogels suitable for protein recovery from soybeans and for novel drug‐delivery devices.

Direct evaluation of chemical potentials in substitutional solid solutions from Monte Carlo simulations

Abstract A new method for the rapid, direct evaluation of the component chemical potentials in substitutional solid solutions from a single Monte Carlo simulation is described. The method is carried out by using the removal or addition of a test-site. The reliability of the test-site method is evaluated for binary solutions on a square lattice with first and second nearest-neighbour interactions and on the b.c.c. lattice with nearest-neighbour interactions. The results obtained are compared with those from the exact solution (for the equi-atomic composition on the square lattice) and with those obtainable from Monte Carlo simulations by less direct routes. Both above and below the critical temperature the new method is found to be highly satisfactory. The new method has a distinct advantage over previous methods in being equally applicable to the calculation of component chemical potentials in multi-component solutions.

Basic equations of the modern thermodynamic calculation of interface properties (MTCIP) theory and their relation to the thermodynamic wave theory and Gyarmati's other basic results

The “Modern Thermodynamic Calculation of Interface Properties” (MTCIP) theory and calculational method is being developed by the authors. In its basic equations the local (interface sublayer) component chemical potentials contain three “unusual” terms reflecting the strongly inhomogeneous character, the constrained existence of the interfaces and the so-called “microstructural parameters”. The use of these terms is—a posteriori—examined and justified on the basis of some from Gyarmati's basic results in the development of Modern Thermodynamics permitting the description of systems even far from equilibrium. In special, considerations and equations related with the famous Thermodynamic Wave Theory and those on the thermodynamic constraint forces are used. In this way the theoretical basis of the MTCIP method is now confirmed by Gyarmati's well-established basic thermodynamic achievements.

An analysis of gas-water-rock interactions during boiling in partially saturated tuff. Analyse des interactions vapeur-eau-roche durant l'ébullition dans un tuff partiellement saturé

Equilibrium geochemical speciation and mass transfer calculations show that porewaters analogous to those in the candidate high-level nuclear waste repository at Yucca Mountain, Nevada, can be strongly affected by open-system boiling. A modified Rayleigh distillation equation appropriate to reactive volatile species is derived and applied to calculate pH ranges during C02-H20 volatilization in a system of fixed alkalinity. Variations in pH by as much as + 2,3 units are caused by volatile weak electrolyte interactions as C02(g) exsolves from the aqueous phase. Protolysis reactions and precipitation of secondary minerals moderate the calculated increases in pH by less than 1 unit. The host rock mineralogy can be altered by boiling because differences in the chemical potentials of components in the aqueous phase and in minerals are created by pH changes. Experiments using pressurized carbonated solutions in closed systems may be inappropriate for simulating water-rock interactions in the proposed repository.

製鋼用各種転炉内におけるスラグと溶鋼中の成分の化学ポテンシャル

製鋼用各種転炉内におけるスラグと溶鋼中の成分の化学ポテンシャル

Fluctuation thermodynamic properties of reactive components from species correlation function integrals

Completely general expressions are given for the equilibrium composition fluctuation properties of systems of components that can undergo reactions (dissociation, association, ionization, solvation) to form new species. Concentration derivatives of the component chemical potentials obtained for non-reacting systems by Kirkwood and Buff are expressed for reacting systems in terms of integrals of the total correlation functions and of the direct correlation functions between the species. This formalism leads to rigorous expressions necessary for modelling fluctuation properties in electrolyte solutions, and in solution theories such as the chemical theory and the solution of groups method for activity coefficients. It is shown that the total correlation function integrals implicitly contain the long range effects of the reactions, but that the direct correlation function integrals (DCFI) do not. Rather, the projection operators for the species DCFI contain the reaction thermodynamics explicitly.

Quantitative simultaneous fit to the liquidus surface and thermodynamic data for the GaInSb system using an associated solution model for the liquid

The liquidus surface and extensive thermodynamic properties in the Ga-In-Sb system are fit simultaneously in a quantitatively satisfactory manner. The Ga uIn l-uSb solid solution phase is described as quasiregular in the components GaSb and InSb. The liquid phase is assumed to consist of the species, Ga, In, Sb, GaSb, and InSb which contribute to the excess Gibbs energy of mixing by quadratic and cubic terms in the species mole fractions. The simplest version of this model that leads to an asymmetric behavior of the component chemical potentials in the Ga-Sb and In-Sb systems is identified and found to be adequate. Contrary to common usage in the literature it is not assumed a priori that the relative (to its pure liquid elements) heat capacity of CaSb(s) (or InSb(ℓ)) is equal to that of GaSb(ℓ) (inSb(s)). This assumption is generally incorrect for associated solution models. Moreover, the parameters of the liquid phase are constrained so that the enthalpy and entropy of mixing of GaSb(ℓ) at the melting point of GaSb(s) are properly related to the enthalpy and entropy of formation of GaSb(s). Two similar constraints are used for InSb(l).

3] Measurements of preferential solvent interactions by densimetric techniques

Publisher Summary This chapter discusses densimetric techniques to measure preferential solvent interactions. The determination of preferential interactions by densimetry requires the measurement of the density increment under two sets of circumstances namely, at constant m3 and at constant μ3. The chapter provides the formula for density increment measured under conditions at which the molal concentrations of diffusible species are kept identical in the solvent and the macromolecule solution. This results in a partial specific volume of the macromolecule in the given solvent without any consideration of interactions between it and components of the solvent. This is referred to as the “partial specific volume at constant molality.” Operationally, this is done by measuring the densities of pure solvent and of a protein solution dissolved in it. The chapter provides formula for density increment measured under conditions at which the chemical potential of component is kept identical in the solvent and the macromolecule solution. This results in an apparent partial specific volume of the macromolecule in chemical equilibrium with solvent components. This is referred to as the “partial specific volume at constant chemical potential.” Operationally, this is obtained by bringing the macromolecule solution to dialysis equilibrium with solvent and measuring the densities of the dialyzed protein and the dialysate.