Mixing properties in the continuous solid solution of the system (CsNO3 + TlNO3) at T = 473 K

•Alkali nitrates are potential materials for the storage of thermal energy.•Mixing enthalpies of solid solutions Cs1−x TlxNO3 are determined for the first time.•The method used is the solution calorimetry in molten salt solvent at T = 473.15 K.•The measurements have been lead with drop calorimeter.

Previous work on the binary phase diagram (CsNO3 + TlNO3) showed, in particular, the existence of a continuous solid solution, CsxTl1−xNO3. It extends over the whole composition range between T = 430 K and T = 480 K. Mixing enthalpies of the solid solutions CsxTl1−xNO3 are measured at T = (473 ± 1) K, for the first time, by using a drop calorimetric method. They exhibit a positive and asymmetrical deviation from ideality.