Gibbs Phase Rule in Systems with Surfaces

Gibbs Phase Rule in Systems with Surfaces 

The origin of Gibbs phase mle in thermodynamics is fairly easily deduced. It is not necessary to totally derive it here since it is available in almost any physical chemistry text (for example, see [20] p. 391). Disregarding the surface as important the phase mle reads 

Consider, for example, the bulk case where there is only one phase and one component. For example hydrogen in a container then the temperature and pressure may be varied arbitrarily provided, of course, the container can be made larger or smaller. This is what is meant by two degrees of freedom. If one has both a liquid and gas present, then the temperature and pressure are interdependent. This lowers iV to 1. 

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