Direct Determination of Standard Gibbs Energies of the Formation of 4CaO·P₂O₅ and 3CaO·P₂O₅ by Transpiration Method

Abstract

The standard Gibbs energy changes of the following reactions have been measured by using transpiration method;


The standard Gibbs energies of the formation of 4CaO·P₂O₅ (ΔG°_{f,(4CaO·P2O5)}) and 3CaO·P₂O₅ (ΔG°_{f,(3CaO·P2O5)}) have been derived as follows;


The reasons for discrepancies from reported values were discussed from the view point of whether the activity of phosphorus is measured directly or not.