Enthalpies of crystallization of lithium alumino-silicate glasses were determined by solution calorimetry at 298 K in HF/HNO3 mixtures. The crystallization was accompanied by an irreversible change of the ionic conductivity. The larger crystallization enthalpies of lithium glasses in comparison with sodium glasses could be correlated with the crystal chemistry and the radius of the alkaline cation. Different AgI modifications were observed in AgCl-AgI composites. The solution calorimetric investigation at. 298 K in aqueous solutions of Na2S2O3/NH3 gave data on phase transition enthalpies of AgI. Metastable modifications can be stabilized by partial intermixing, small particle sizes or the influence of interfacial energies and strain.