Collect. Czech. Chem. Commun. 1983, 48, 1528-1531

Alkali vapor pressures over some simple silicate melts

Vincenzo Piacentea and Josef Matoušekb

a Istituto di Chimica Fisica, Universita di Roma, Italy
b Prague Institute of Chemical Technology, 160 00 Prague 6


Mass spectrometric analysis of gaseous phase above Na2O.4 SiO2; K2O.4 SiO2 and Na2O.K2O.8 SiO2 melts was used to identify the species observed and to determine their partial pressure values. The principal species observed were the corresponding alkaline species and oxygen. The temperature dependence of sodium and kalium partial pressures was established and corresponding vaporization enthalpy values were calculated by second law treatment of those vapor data. The average value of sodium vaporization enthalpy in binary melt amounts of ΔHT0 = 315 ± 10 kJ mol-1 being in a good agreement with the data published previously. The vaporization enthalpy of potassium ΔHT0 = 142 ± 8 kJ mol-1 is considerably lower with comparison to sodium and does not change if potassium evaporates from binary K2O.4 SiO2 or ternary Na2O.K2O.8 SiO2 melts respectively.