Determination of the Critical Points for Intercalating Systems by the EMF Method Concerning Foreign Metal.

The work is devoted to the study of the possibility of determining the critical points of phase diagrams by measuring the EMF of electrochemical cells relative to a metal that is not part of the test substance. The measurement results of the concentration dependences of the EMF for the CuxTiS2 system in the electrochemical cells Na|Na+|CuxTiS2 and Cu|Cu+|CuxTiS2 in the concentration range 0 < x < 0.7 are compared. It was determined that the chemical potential of the ion is independent of x in a satisfactory approximation. The EMF difference in the given cells is close to the standard electrode potentials difference for respective metals. It is concluded that the dependences E(x) for both types of cells are similar and correlated. Therefore, one can choose any convenient metal for measurements of this kind. Using the example of measuring EMF in electrochemical cells for the FexTiSe2 system concerning sodium and lithium, we showed that the elastic contribution to free energy is constant over the entire concentration range 0 < x < 0.5.