ABSTRACT
This chapter investigates phase co-existence or phase equilibria. It considers a system of n independent components capable of coexisting in F phases. The chapter provides phase equilibrium only between a pair of phases, say the ones labelled by i and j. Before equilibrium is achieved there will be transfer of various components between the two phases. It describes two phases of water in coexistence, say water and ice or water and its vapor. The single degree of freedom to describe the coexistence of two phases of the same component can be chosen to be either the pressure or temperature. The chapter looks at the solid-liquid coexistence curve. By and large liquids are less dense than solids and if the slope of the coexistence curve is dictated by it as in the above two cases, then the freezing curves should also have positive slope.
