ACTIVITIES AND TERNARY PHASE-DIAGRAMS

A set of theoretical formulae for calculating activities along the liq uid surface in ternary phase diagrams has been presented. These formul ae are rigorous since no assumption is made in the derivation. The exp ressions are generalized and can be simplified to the forms presented by Pelton, Chou, Elliott and Gokcen under certain conditions. In pract ice, the activity of the components are desired at a fixed temperature instead of a variable temperature like that along a liquid surface. U nder this situation, with reasonable assumptions the equations can be further simplified such that they do not contain any partial thermodyn amic properties. Activities can then be readily calculated from phase diagrams. The method presented in this paper is for a ternary system a nd can be extended to multicomponent systems.