Currently, the relevance of using more advanced and universal chemicals in the creation of electrolytes of heat carriers of non-melting salt mixtures and thermal batteries is increasing. Based on this, it can be stated with confidence that the halide and nitrate salts of s1-elements have the greatest potential in this direction. When developing the latest generators of electrical and thermal energy, such chemicals have a unique property - the abil-ity to run power plants even at low temperatures. For a wide practical application of melts of halides and nitrates of s1 elements with specified values of thermodynamic characteristics and physico-chemical properties, the study of phase diagrams is required. The method of differential thermal analysis was used to study the phase equilibrium of salt systems of the following type: Li,Rb||I, NO3, Li,K||Br,NO3, Li,K||I,NO3, Li, K||F,NO3, Li, K||Cl,NO3, Li,Rb||Br,NO3, Li,K||Br,NO3, Li,Na||I,NO3, Li,Rb||F,NO3. A comparative analysis of the series of three-component mutual systems formed from the systems experimentally studied by the authors of the article Li,K||F,NO3, Li,K||Cl,NO3, Li,K||Br,NO3, Li, K||I,NO3, Li,Na||F,NO3, Li,Na||I,NO3, Li,Rb||F,NO3, Li,Rb||Br,NO3, Li,Rb||I,NO3,Li,Cs||F,NO3, Li,Cs||Cl,NO3, Li,Cs||I, NO3 and systems studied by other authors Li,Na||Cl,NO3, Li,Na||Br, NO3, Li,Rb||Cl,NO3, Li,Cs||Br,NO3. The considered eutectic compositions of salt systems can be used to create a molten source of RHIT.