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.