The adsorption theory of electrolytes and the volumetric properties of some nitrate-water systems. From fused salts to dilute solutions

On the basis of the Brunauer-Emmet-Teller adsorption model extended by Stokes and Robinson to concentrated electrolyte solutions, from the Stokes-Robinson equation for water activity, and from the Abraham equation for electrolyte activity, Ally and Braunstein have derived equations for the partial excess molar volumes of salt and water in salt-water systems. In their equations, only one BET parameter is considered to be pressure dependent. In the present publication, complete equations are proposed, taking into account the dependence of both BET constants on pressure. These equations are tested successfully with nitrate-water systems containing mono and divalent cations over a concentration range from fused salts to water: [0.500 LiNO3-0.500 KNO3+H2O], [0.467 TlNO3-0.214 CsNO3-0.319 Cd (NO3)(2)+H2O], [N(C2H5)(4)NO3+H2O]. [0.515 AgNO3-0.485 TlNO3+H2O], and [AgNO3-TlNO3-M (NO3)(n)+H2O] (M=Na, K, Cs, Cd, Ca; x(AgNO3)/x(TlNO3) as in the preceding system x(M) being varied from 0.025 to 0.125 depending on the cation). Additivity rules which involve the partial derivatives of the BET constants with respect to pressure are also proposed.