Abstract: New equations for the physical adsorption of gases on solids have been developed based on the vacancy solution model of adsorption in conjunction with the Flory-Huggins activity coefficient equations. The isotherm equation contains three regression parameters: a Henry's law constant, the limiting amount of adsorption, and a gas-solid interaction term. Pure-gas data over a range of temperature can be correlated using only five parameters. Gas-mixture equilibria can be predicted using only the parameters obtained from the pure-gas data. Pure-component, binary, and ternary adsorption equilibrium data on activated carbons, silica, and zeolites over a wide range of conditions have been used to evaluate the model. The results show that, except for a few systems, this model predicts gas-mixture equilibria better than any other model.

Abstract: A consistent set of thermochemical property values at 298.15K is given for the known constituents of aqueous sulfur dioxide. Also tabulated are values of the mean ionic activity coefficients, osmotic coefficients, partial pressure of SO/sub 2/(g), and the relative apparent molar enthalpy as a function of concentration of SO/sub 2/(aq) at 298.15K. The data analysis considered a wide variety of measurement techniques: calormetric enthalpies of solution and reaction, heat capacities, equilibrium constants, solubilities, and vapor pressure measurements, both partial and total, over aqueous solutions of SO/sub 2/ for the temperature range 278 to 393K. All auxiliary data have been taken from the most-recent set of CODATA values which were converted to a standard-state pressure of one bar (0.1 MPa). Parameters are given which extend the predictions to temperatures up to 373K.

Abstract: For clinical purposes the activities of Na+ and K+ obtained with ion-selective electrodes in undiluted whole blood or serum should be multiplied by an appropriate factor to obtain the same values as the substance concentrations obtained by flame photometry. The factor is primarily dependent on the mass concentration of water in normal plasma divided by the molal activity coefficient of Na+ (or K+) of normal plasma. We discuss the value of the molal activity coefficient of Na+ obtained by theoretical calculations and by direct measurement. The discrepancies between theory and measurement (gamma Na+ of 0.747 and 0.73, respectively) may be due to some binding of Na+ (protein binding or ion pair formation), a small and variable residual liquid-junction potential, or certainty about the appropriate value for the ionic strength of normal plasma (0.16 mol/kg or somewhat higher).

Abstract: Pitzer's equation for the activity coefficient has been applied to LiCl, NaCl, KCl, RbCl, CsCl, and HCl in methanol-water mixtures at 25°C. The two parameters, β MX (0) and β MX (1) , were obtained by the method of least squares. The same values of b and α as for aqueous systems could be used for the methanol-water mixtures without greatly affecting the standard deviation of the fit. β MX (0) was found to decrease with methanol content for the alkali metal chlorides whereas β MX (1) was found to increase. For HCl, however, a slight maximum and a minimum were found in the values of β MX (0) while a maximum was observed in the values of β MX (1) .

Abstract: A disordered system is described by a model in which interstitials can occupy sites of different energy. Tracer diffusion occurs in the absence of a concentration gradient and by jumps over energy barriers with the same saddle point energy. Using statistical mechanics and simple random walk considerations the tracer diffusion coefficient is D∗ = γ0D0 where D0 is the known or unknown tracer diffusion coefficient of an arbitrary reference state, and γ0 is the activity coefficient with respect to the same reference state. The activity coefficient γ0 can be calculated for a given energy distribution. The results are in agreement with rigorous treatments of diffusion for the same potential trace. It is shown that Henry's law (γ0 → constant for c → 0) is valid for small interstitial concentrations c and for all types of energy distributions. Thus the diffusivity also becomes independent of concentration for c → 0. Measurements of the hydrogen diffusion coefficient in liquid-quenched and vapour-quenched Pd80Si20 and its dependence upon temperature and hydrogen concentration are presented. These are in excellent agreement with the model if a Guassian distribution of energies is assumed. The width of the energy distribution is different for the two materials, but in each case agrees with results from solubility measurements. For alkali ions in oxide glasses two energy levels, one for sites adjacent to the immobile anions and one for sites far away from them, describes the so-called “weak electrolyte behaviour”, which determines diffusivity and conductivity at low alkali contents. With increasing alkali content the energy distribution changes, and predictions were made, which are in agreement with experimental findings in borate-silicate and GeO2-glasses.

Abstract: Equations are given and procedures described for calculating liquid junction potentials over wide ranges of concentration and composition. Use is made of the Henderson continuous mixtures assumption, avoiding treatment of the codiffusion problem. Ionic mobilities and activities are incorporated realistically, making use of standard data on binary electrolyte solutions. For ionic strengths up to about 0.1, an equation is derived in terms of ionic properties specified for the two end solutions; typical accuracy is 0.1 mV for simple junctions between two concentrations of the same electrolyte, and 1-2 mV for more complex junctions. Higher concentrations require specification of ionic properties at points intermediate between the end solutions; approximations are developed which prove accurate to about 0.5 mV in simple cases at ionic strengths as high as 5, while in complex cases an accuracy of 1 to a few mV is found at ionic strengths as high as 4.5. Ionic strength ratios across the junctions examined range from 1:1 to 94:1, typically being about 20:1. A rule is given for determining mobilities and activities of ions in mixtures, using standard data for binary solutions. An expression is obtained for the activity coefficients of single ion constitutents in terms of mean activitymore » coefficients, and an estimate of the associated error is derived. This is the error in dividing total cell potentials into a component due to electrode potentials and a component arising at the liquid junction; it appears to be of comparable magnitude to the errors, stated above, due to other approximations in the calculations described.« less

Abstract: The mean activity coefficients of solutes such as H2SO4 and Fe2(SO4)3 in the solution system H2SO4-Fe2(SO4)3-H2O, and HCl and FeCl3 in the solution system of HCl-FeCl3-H2O at 298 K were calculated by the McKay-Perring method using the water activities of these solution systems. The mean activity coefficients calculated by the McKay-Perring method were sufficiently accurate for use on concentrated mixed solutions. A Gibbs-Duhem equation, which is applicable for calculating mean activity coefficients of one component using the activity data of the other components, was also used to calculate the mean activity coefficient of Fe2(SO4)3 in aqueous solutions of H2SO4-Fe2(SO4)3 by using both the activity of water measured by an isopiestic method and that of H2SO4 determined by the McKay-Perring method. The Gibbs-Duhem method was more tedious for calculation than the McKay-Perring method, and it required thermodynamic data other than water activities.

Abstract: Highly precise vapor pressure-solubility data have been obtained for benzene in aqueous solutions of sodium octylsulfate (SOS) containing approximately 0.4 M sodium chloride, at 15, 25, 35, and 45°C. A mass action model, using a form of the Poisson distribution equation modified to include cooperative benzene-benzene interactions within the micelle, provides an excellent fit of the solubilization data at each temperature. Values are reported of equilibrium constants for the interaction of a single benzene molecule with micellar SOS, the cooperativity parameters in the Poisson model, and activity coefficients for benzene solubilized in the micelle. A comparison of the solubilization results with those obtained for SOS solutions with no added salt indicates the influence of NaCl on properties of the micelles and micelle solubilizates. As has been reported previously, careful measurements of the dependence of extent of solubilization on the solubilizate activity indicate that solute-solnte interactions within the micelles lead to significant departures from Henry's law.

Abstract: The thermodynamic properties of molten NaNaBr mixtures were determined at 800°C for concentrations of Na up to 5 atom-% using an emf technique with CaF2 solid electrolyte. Concentrations were controlled by the method of coulometric titration. The activity coefficient is found to pass through a maximum at 0.5 atom-% Na. An atomic model is presented to explain the thermodynamic results of these solutions. It predicts the concentration dependence of the number of F-centers as well as the number of F-center associates, e. g., dimers. Calculations using the model also explain results from spectroscopic, magnetic, and electrical conductivity measurements quantitatively.

Abstract: In the ideal associated solution model, activity coefficients of all species (labelled A, B, and AB here) are taken to be unity at all mole fractions and all temperatures, with several derivative consequences that have not previously been investigated. We have applied this model to an analysis of the thermodynamic properties (vapor pressures, excess volumes, excess enthalpies, partial molar enthalpies of solution, and excess heat capacities) of the chloroform + triethylamine system in terms of K, ΔV⊖, ΔH⊖, and ΔCp⊖ for the equilibrium represented by A+B=AB. It is shown that there is good consistency between the relatively simple chemical ideal associated solution model and all available thermodynamic data except heat capacities, for which the consistency between model and data is less good. Some limitation of the ideal associated solution model are discussed, along with the relationship of this model to hydrogen bonding in the AB complex and to spectroscopic investigations. New thermal (partial molar enthalpies of solution and excess heat capacities) and volumetric data are presented.

Abstract: A lithium probe has been used for the determination of the lithium content of molten aluminum alloys. The electrolyte is a two-phase mixture of Li3PO4 and Li4Si04 to give an overall composition of Li3.6Si0.6P0.4O4. This electrolyte was found to be slightly attacked by pure liquid lithium, but no attack was detected in the aluminum-lithium melts. However, exposure to high humidity caused the electrolyte to degrade. A satisfactory reference electrode was found to be decomposed Li2Ti307 consisting of Li4Ti5O12 and TiO2. An activityvs composition plot showed that Henry’s law was obeyed, and the activity coefficient was 0.17 at 984 K and 0.26 at 1050 K.

Abstract: Solubility data of organic probes in polydimethylsiloxane (PDMS) and polyisobutylene (PIB) obtained by inverse gas chromatography (IGC) were collected from the literature and analyzed. Applying the principle of corresponding states, empirical correlations were derived and presented for the estimation of solubilities of nonpolar and slightly polar probe molecules in these polymers. Estimation of other thermodynamic properties, such as activity coefficient of the solute, Henry's law constant, Flory–Huggins interaction parameter, and heat of solution through the use of these correlation equations, was demonstrated.

Abstract: The thermodynamics of the Na-Al (99.5%) system has been investigated over a range of temperatures. Measurements were made using Nasicon (Na3Zr2Si2PO12) and sodiumβ-alumina with Nao.75Co02 as the reference material. Near to the melting point there is a strong dependence of the activity coefficient on the sodium concentration whereas, at higher temperatures, Henry's Law is obeyed and the activity coefficient agrees with other determinations.

Abstract: The values of sulfur activity in the liquid S-Fe-Co-Ni system were determined from unpublished equilibrium data for H2 +S (in alloy) = H2S. The activity coefficient of sulfur varied from 0.387 to 1.896 and increased with increasing concentrations of Fe and Co. The published values for the activities in the binary systems Fe-Co, Fe-Ni, and Co-Ni were used to calculate the activities in the ternary Fe-Co-Ni alloys, and these results were expressed as a function of composition. This function was used with the activity coefficients of S in the binary metal solvents to express the activity coefficient of S in the ternary metal solvents as a function of mol fractions of Fe, Co, and Ni. The experimental values for S in Fe-Co-Ni agreed well with the calculated values based on the binary metal solvents, and this showed that all the activity values were consistent.

Abstract: In an earlier study, the activity coefficients of aqueous mixtures of HCl with the hydrochlorides of tris(hydroxymethyl)aminomethane (Tris) ort-butylamine (t-B) were determined at ionic strengths of 0.1, 0.5, and 1.0 mol-kg−1. The work has been extended to ionic strengths of 2.0 and 3.0 through emf measurements with hydrogen and AgCl/Ag electrodes at 25°C. The results are considered in terms of Harned's rule and the Pitzer and Rush-Johnson-Scatchard treatments of activity coefficients in electrolyte mixtures. In order to compare ionic interaction parameters in the two systems, the activity coefficients and osmotic coefficients of t-butylammonium chloride at molalities up to saturation (7.14 mol-kg−1) were determined by the gravimetric isopiestic method with solutions of NaCl as reference. The behavior for both systems can be accounted for satisfactorily in terms of binary (H+−N+) and ternary (H+−N+−Cl−) interactions, where N+ is either Tris·H+ or t-B·H+.