Room temperature grinding of nine kinds of powder mixtures prepared by the combination of alkaline earth metal sulfates (M-SO4, M = Ca, Sr and Ba) and alkali metal hydroxides (R-OH, R = Li, Na and K) was conducted in a planetary ball mill. The ground products were characterized mainly by X-ray diffraction analysis. LiOH . H2O powder reacts with CaSO4 . 2H(2)O, forming a mixture of Ca(OH)(2) and Li2SO4 powders, while LiOH . H2O reacts with neither SrSO4 nor BaSO4 powders. NaOH as well as KOH powders react substitutionally with each sulfate. The reaction and non-reaction systems are distinguished by negative and positive values in the calculated standard Gibbs free energy change, respectively. In the present systems, the standard free energy change is an indicator governing the substitution reactions. Grinding operation in the reaction systems plays a significant role to facilitate their forward reaction.