The division of the four-component reciprocal system Na+, Rb+, Cs+ || F−, NO3− into stable elements was carried out for the first time. The phase tree, confirmed by the experimental data from the differential thermal analysis, was constructed. The chemical interaction in a yet unexplored faceting element, i. e. in the three-component reciprocal system Na+, Cs+ || F−, NO3−, and in the four-component reciprocal system was studied.
