Thermodynamic measurement of aluminium phosphate by double Knudsen cell mass spectrometry

The ion currents of gaseous phosphorus oxides in equilibrium with a mixture of Al2O3·P2O5 and Al2O3 at T = (1473 to 1573) K were measured by double Knudsen cell mass spectrometry. The Gibbs free energy changes of the following reactions estimated in comparison with the ion currents from a mixture of (MgO)3·P2O5 and MgO are as follows:Al2O3(s)+P2(g)+52O2(g)=Al2O3·P2O5(s),ΔG∘/J=-1970000+574T/K(±28000)for(1473