Abstract
The relative partial molal free energy of gallium and the activity of gallium in the compound 
have been obtained across the homogeneity range of this phase at 835° and 900°C. A solid state anion conductor (
) was used as the electrolyte in a high temperature galvanic cell. It was found that the thermodynamic properties of 
change rapidly near 50 atom per cent gallium. A brief review is made of the metal/oxide equilibria and the free energies of the two gallium oxides 
and 
.