Emf measurement of formation cells provides an efficient means to obtain th
e thermodynamic properties of electrolyte solutions in fused salts. The exp
eriments were extended to the determination of the thermodynamic properties
of metallic solid solutions. The activity of NiCl2 and FeCl2, and the ther
modynamic properties of solid solutions Ni-Pt were investigated in fused Li
Cl-KCl and NaCl-KCl.