Tables are presented here of values of thermochemical properties and processes at 298.15/sup 0/K for some substances of interest to DOE for flue gas desulfurization. The substances covered are (1) the aqueous ions: OH/sup -/, SO/sub 3//sup -2/, HSO/sub 3//sup -/, SO/sub 4//sup -2/, HSO/sub 4//sup -/, CO/sub 3//sup -2/, HCO/sub 3//sup -/, H/sup /, Mn/sup 2/, Fe/sup 2/, Mg/sup 2/, Ca/sup 2/, Na/sup /, and K/sup /, and (2) solid, liquid, aqueous, and gaseous compounds or species formed from these ions. The tables contain the following: (1) the thermochemical property values, enthalpy of formation, ..delta../sub f/H/sup 0/, Gibbs energy of formation, ..delta../sub f/G/sup 0/, entropy, S/sup 0/, and heat capacity, C/sub p//sup 0/, all at 298.15/sup 0/K, as well as the enthalpy difference between 298.15/sup 0/K and 0/sup 0/K, H/sup 0/-H/sub o//sup 0/, for the basic species cited above; (2) the predicted values for ..delta..H/sup 0/, ..delta..G/sup 0/, ..delta..S/sup 0/, and ..delta..C/sub p//sup 0/ as well as log K (equilibrium constant) for the processes, or reactions, of importance to DOE, calculated from (1,7522 ); (3) the property values, phi/sub L/, the relative apparent molar enthalpy, ..gamma../sub -/, the mean ionic activity coefficient, and phi, the osmotic coefficient, for the binary aqueous systems at 298.15/sup 0/K, all as a function of concentration. Some documentation for (2) and (3) is provided. All of the values given are consistent with the NBS TN 270 Series.