Calorimetric determination of the enthalpy of formation for pyrophyllite

A calorimetric study of the natural pyrophyllite was performed by high-temperature melt calorimetry on a Tian-Calvet calorimeter. Based on experimentally determined in this work for pyrophyllite and gibbsite, as well as previously obtained for corundum and quartz, the total value of the enthalpy increment for the sample heated from room temperature to 973 K and the enthalpy of dissolution at 973 K by Hess's law, the enthalpy of formation of pyrophyllite of Al-2[(OH)(2)/Si4O10] composed of elements was calculated at 298.15 K: Delta(f) H (el) (o) (298.15 K) = -5639.8 +/- 5.7 kJ/mol.