The property of the systems MCl-CaCl ₂ and MCl-CaCl₂-CaO (where M is a alkali metal) allow its used in many processes of modern industry, in particular for the production of metals. However, in spite of this the information on the diagrams of the state of ternary systems of MCl-CaCl₂-CaO and the behavior of refractory metal oxides in these melt is extremely limited.

This work shows the results of thermal analysis of partial cuts the ternary system NaCl-CaCl₂-CaO.

The table 1 shows the compositions and the melting point (crystallization point) characteristic points of the system NaCl-CaCl₂-CaO.

Table 1. The composition and melting point (crystallization point) of characteristic points.

System	T °C	Concentrate and I component in , %			The character of the point
		Na Cl	CaO	CaCl 2
Na Cl - CaCl 2	500	0.490	-	0.510	Eutectic ( e 1 )
CaO - CaCl 2	750	-	0.065	0.935	Eutectic ( e 2 )
	835	-	0.185	0.715	Peritectic ( p 2 )
	500	0.470	0.05	0.480	Eutectic ( E )

The results of investigation partial cuts ternary system showing that in the concentration range 0–20 mol.% CaO ternary system NaCl-CaCl₂-CaO is eutectic. The composition of eutectic (in mol.%) is NaCl(0.47)-CaCl₂(0.48)-CaO(0.05) and its molten point is 480 °C. In the fused samples the phases of the initial components of the system are identified. Solid solutions and phases of the composition Ca(OCl)₂ was not detected.