The thermodynamic properties of radium

The enthalpy, Gibbs free energy, and entropies of aqueous radium species and radium solids have been evaluated from empirical data, or estimated when necessary for 25°C and 1 bar. Estimates were based on such approaches as extrapolation of the thermodynamic properties of Ca, Sr, and Ba complexes and solids plotted against cationic radii and charge to radius functions, and the use of the Fuoss or electrostatic mathematical models of ion pair formation (Langmuir, 1979). Resultant log K(assoc) and ΔH0(assoc) (kcal/mol) values are: for RaOH+0.5 and 1.1; RaCl+−0.10 and 0.50; RaCO032.5 and 1.07; and RaSO042.75 and 1.3. Log Kspand ΔH0(dissoc) (kcal/mol) values for RaCO3(c) and RaSO4(c) are −8.3 and −2.8, and −10.26 and −9.4, respectively.