Determinations of partial vapour pressures and isopiestic measurements have been carried out on aqueous solutions of nitric acid and of perchloric acid. In the case of nitric acid the measurements cover the rangc it1 = 2-28 mol kg-l at 25 "C, 50 "C and 75 "C; for perchloric acid the range rrr = 0.1-14 mol kg-1 was studied at 10 "C and 40 "C and rn = 0.1-16 mol kg-1 at 25 "C. Osmotic coefficients, stoichiometric mean activity coefficients and related thermodynamic functions arc derived from the experimental data. In the case of perchloric acid at 25 "C values of the relative partial molar enthalpy of the electrolyte were also obtained. Thc stoichiometric activity coefficients at 25 "C for both systems are fairly well represented by a previously proposed equation with three adjustable parameters. With the aid of literature data for the degrees of dissociation of both acids, values of the following quantities were obtained: dissociation constants, standard affinities, enthalpies and entropies of dissociation, mean ionic activity coefficients and activity coefficients of the undissociated portion of electrolytes.
Einleitung
We discuss diffusion (including sedimentation) and thermal diffusion in the critical region (both for liquid‐liquid and vapour‐liquid equilibria) of binary fluid systems. In particular, we present diagrams and discussions of experimental values of diffusion coefficients, sedimentation coefficients, and thermal diffusion factors for the liquid systems n‐hexane + nitrobenzene (with upper consolute point) and water + triethylamine (with lower consolute point), both at 1 bar, and for the fluid system methane + propane at about 73°C in the critical vaporization region. In the last case, we check a formula proposed by the author in 1950.
Calorimetric measurements of the heats of mixing for the liquid system water+acetic acid at 17 °C, 20 °C, 25 °C, 30 °C, 40 °C, and 50 °C show that there is a change of sign in the function H̅E(x), where H̅E denotes the molar heat of mixing and x the mole fraction of acetic acid. The process of mixing the pure liquid components is weakly exothermic for low acid concentrations, but strongly endothermic for high acid concentrations. The function H̅E can be approximately represented by the usual power series with respect to x, five free parameters at each temperature being necessary.
Results of measurements of the viscosity and of the molar volume for the ideal liquid system chlorobenzene + bromo-benzene are presented. They cover the whole composition range between 0 °C and 80 °C. Both the composition and the temperature dependence of the viscosity are discussed.
Vapour pressures and vapour compositions of the liquid system water + acetic acid have been measured at 25 °C, 30 °C, 35 °C, 40 °C, and 45 °C in the whole range of compositions. The dimerization of acetic acid in the vapour being taken into account, the molar excess Gibbs function ḠE is derived from the measurements. Earlier measurements of the molar excess enthalpy HE are combined with the -GE values to give the molar excess entropy SE. The “symmetry rule” (Haase, 1951) concerning the composition dependence of ḠE, -HE, and S̄E has been confirmed.
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