This paper reports that the standard enthalpy of formation of potassium metasilicate (k2sio3), determined by hydrofluoric acid solution calorimetry, was found to be ahf,298 deg = -363.866 +/- 0.421 Kcal mol-1 (-1522.415 +/- 1.762 Kj mol-1). The standard enthalpy of formation from the oxides was found to be ah298 deg = - 64.786 +/- 0.559 Kcal mol-1 (-271.065 +/- 2.339 Kj mol-1). These experimentally determined data were combined with data from the literature to calculate the Gibbs energies of formation and equilibrium constants of formation over the temperature range of the literature data. The standard enthalpies of formation and Gibbs energies of formation are given as functions of temperature. The standard Gibbs energy of formation is agf,298.15 Deg = -341.705 Kcal mol-1 (-1429.694 Kj mol-1).