Engineering Chemistry

8

PHASE RULE

8.1 INTRODUCTION

In 1875, as a result of mathematical and thermodynamic studies, J. Willard Gibbs put forward a rule known as Phase Rule; without any exception, the rule is applicable to all heterogeneous system in equilibrium. By using Phase Rule, the effect of temperature, pressure and concentration can be predicted qualitatively on a heterogeneous system, which is in equilibrium by the Phase diagrams.

It is assumed that the equilibrium is influenced only by temperature, pressure and concentration, but not influenced by gravity, electrical or magnetic forces or by surface action. The maximum number of degree of freedom is taken as three; mathematically, Gibbs’ Phase Rule may be stated as:

8.2 EXPLANATION OF THE TERMS INVOLVED ...