a) Condensed phase rule

b) Triple point

a) Condensed phase rule:

In some systems, an equilibrium exists between solid - liquid phases and gaseous phase is practically absent. Hence the effect of pressure on such system can be neglected. Then it is necessary to take into account only two variables viz. temperature and concentration.

Such system showing solid-liquid equilibrium is called condensed system and phase rule applied to such systems is as follows:

F = C – P + 1 … known as condensed phase rule.

b) Triple point:

Triple Point is the temperature and pressure at which solid, liquid, and vapor phases of a particular substance coexist in equilibrium.