Eutonic point

Iron-nickel alloys are known to dissolve in the aluminium melts non-selectively. " As seen from Table 5.3, during dissolution of a 50 mass % Fe-50 mass % Ni alloy the ratio, cFe cNi, of iron to nickel concentrations in the melt is 1.00 0.05, i.e. it is equal to that in the initial solid material. The same applies to other alloys over the whole range of compositions. Respective saturation concentrations are presented in Table 5.4. The data obtained display a strong mutual influence of the elements on their solubilities in liquid aluminium because in its absence the solubility diagram for a constant temperature would be like that shown by the dotted lines in Fig. 5.5, with the eutonic point, E, at 2.5 mass % Fe and 10.0 mass % Ni. The effect of iron on the nickel solubility is seen to be more pronounced than that of nickel on the iron solubility. 

The phase diagram in Fig. 13.18 on the next page is for a ternary system of water and two salts with an ion in common. There is a one-phase area for solution, labeled sin a pair of two-phase areas in which the phases are a single solid salt and the saturated solution and a triangular three-phase area. The upper vertex of the three-phase area, the eutonic point, represents the composition of solution saturated with respect to both salts. Some representative tie lines are drawn in the two-phase areas. 

The solubility isotherm at 25°C was established and the solid phase compositions were determined by Schreinemakers method. The system is eutonic. The eutonic point is at 8.23 wt% Nd2(Se04)3 and 37.16 wt% Yb2(Se04)3. Solid solutions based on Nd2(Se04)3 5H20 are observed for up to 70.09 mol% Yb2(Se04)3 beyond that mixed crystals based on... 

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