The stabilizing influence of a large cation on an unstable anion can be explained in terms of trends in lattice enthalpies. First, we note that the decomposition temperature of solid inorganic compounds can be discussed in terms of their Gibbs energies of decomposition into specified products. In many cases it is sufficient to consider only the corresponding reaction enthalpies, for the reaction entropy is almost constant for the substances being compared. Moreover, as we shall see, the calculations center on differences of lattice enthalpy between the solid reactants and the solid products, for these differences dominate the reaction enthalpy. The differences in lattice enthalpy in turn may be discussed, at least in a general way, in terms of the Kapustinskii equation. Hence the variation in stability may be correlated with the variation of the electrostatic parameter .