year of publication
The purpose of this investigation was to obtain accurate and precise thermodynamic quantities of well-characterized specimens of analcime and dehydrated analcime, and to relate the results to processes of geochemical interest. Calorimetric measurements have been carried out on a pure specimen of analcime whose composition was Na0.96Al0.96Si2.04O6·H2O and on the corresponding anhydride. The low-temperature heat capacity, standard enthalpy of formation (298.15 K), and high-temperature enthalpy increments have been determined by adiabatic, solution, and drop-calorimetric techniques, respectively. Thermodynamic functions have been calculated for analcime (to 600 K) and for dehydrated analcime (to 1000 K). The following values at T = 298.15 K and at a pressure of 1 bar have been obtained:
An examination of the thermodynamics of the following reactions has been carried out in the light of the results obtained in the present study:
analcime = dehydrated analcime + H2O(g)
low albite + H2O(l) = analcime + SiO2(aq)
Work performed under the auspices of the U.S. Department of Energy.