Structure of aqueous electrolyte solutions. Thermodynamic internal pressure

Abstract

The thermodynamic internal pressures of aqueous electrolyte solutions have been analysed using three models (the Tammann–Tait–Gibson, TTG, the orientation defect and the non-interacting homomorph, NIH) together with the infrared (i.r.) and dielectric structural temperatures. The effect of ionic volumes is to change water–water interactions. This leads to a change (increase or decrease) in the internal pressure of the water of p_ww bar. The ionic-charge effects cause an increase in pressure of (p_e–p_lr) bar, where p_e is the TTG effective pressure and p_lr is the long-range pressure (deriving from forces proportional to z²/r and to z²). p_el(a component of p_e and arising from the electrical deformation of the water molecules) plus p_ww are mainly responsible for the changes in pressure associated with the hydrogen-bond energy. The pressure changes associated with second cosphere events can be ascribed to intermolecular forces and small changes in the free OH.