The revised thermodynamic database MALT2 and associated computer programs are described and discussed in terms of requirements for a thermodynamic database from the viewpoint of materials chemistry. The equilibrium approach is discussed from three different aspects; Gibbs energy minimization, mass action law and associated enthalpy considerations, and the construction of chemical potentials. In particular, application of generalized chemical potential diagrams to reactions between condensed materials is discussed with an emphasis on materials compatibility and long term stability such as electrolyte-electrode chemical interactions in high temperature electrochemical cells.