Values of ΔG^⊖_s, ΔS^⊖_s, and ΔC^⊖_ps for solution of gaseous univalent ions in water from 273 to 573 K have been calculated using Abraham and Liszi's method, in which a neutral term is obtained from data on rare gases and an electrostatic term is obtained using a solvation model in which an ion of radius a is surrounded by a solvent layer of thickness (b – a) and dielectric constant ε₁. It is shown that when (b – a) is held constant for a given ion and when ε₁ is obtained from ε₁= 1.87 at 298 K and ∂ε₁/∂T=–1.6 × 10^–3 K^–1 there is good agreement between calculated quantities and those from Tremaine and Goldman at temperatures > ca. 423 K. There is similarly good agreement between ΔC^⊖_ps(calc.) and values from Cobble et al. for solution of (Na⁺+ Cl^–) above 423 K. It is suggested that below this temperature there are effects due to the structure of water that cannot be calculated on an electrostatic theory. It is shown that whereas at 298 K ions may be structure making (Na⁺) or structure breaking (Cs⁺, Cl^–, Br^– and I^–), at temperatures > ca. 400 K all the ions studied (Na⁺, K⁺, Rb⁺, Cs⁺, Cl^–, Br^– and I^–) are structure making. The structure-making and -breaking effects of ions in water as deduced from entropies of solvation may quantitatively be connected with ionic viscosity B coefficients at all temperatures studied (273–423 K).