Structure and thermodynamics in the linear modified Poisson-Boltzmann theories in restricted primitive model electrolytes

Structure and thermodynamics in restricted primitive model electrolytes are examined using three recently developed versions of a linear form of the modified Poisson-Boltzmann equation. Analytical expressions for the osmotic coefficient and the electrical part of the mean activity coefficient are obtained and the results for the osmotic and the mean activity coefficients are compared with that from the more established mean spherical approximation, symmetric Poisson-Boltzmann, modified Poisson-Boltzmann theories, and available Monte Carlo simulation results. The linear theories predict the thermodynamics to a remarkable degree of accuracy relative to the simulations and are consistent with the mean spherical approximation and modified Poisson-Boltzmann results. The predicted structure in the form of the radial distribution functions and the mean electrostatic potential also compare well with the corresponding results from the formal theories. The excess internal energy and the electrical part of the mean activity coefficient are shown to be identical analytically for the mean spherical approximation and the linear modified Poisson-Boltzmann theories.

Solubility of BaSo4 and physicochemical state of barium in seawater

The solubility of barium sulfate in diluted Na2SO4NaNO3 solutions and seawater with 35 salinity at 22C was experimentally studied. Value of the thermodynamic solubility product of barium sulfate = (7.570.87)1011 was ascertain. It was shown that equilibrium concentration of dissolved barium in seawater is equal 30.7 g/l and water layer of the World Ocean is in the state of low undersaturation for BaSO4. Values of the ionic-mean activity coefficient of BaSO4, total activity coefficient and part of free ions of Ва 2+ in seawater, equal 0.108, 0.131, and 0.59, respectively, were determined according to the experimental data.

Solubility in the System (NH4)2S2O8—NH3—H2O and Mean Activity Coefficients of Saturated Solutions of (NH4)2S2O8

Solubility in the System (NH4)2S2O8—NH3—H2O and Mean Activity Coefficients of Saturated Solutions of (NH4)2S2O8The solubility data of ammonium peroxodisulfate in aqueous ammonia solutions at 15.5 °C have been evaluated using the relative activity coefficient expansion. Using the known value of the mean activity coefficient of saturated solution of ammonium peroxodisulfate in pure water, values of the mean activity coefficients of this salt in the saturated solutions of the given system have been calculated.