*S *as function of *V* and *T*. For simplicity, we consider first a pure phase component *i*. Integration of (91) yields

(107)

Expansion in an ideal gas and a deviation term:

(108)

Solving the last integral in (108):

(109)

Extending the lower integration limit:

(110)

The first two terms of (110) are the *S *of an pure* hypothetical ideal gas*. If the system is a mixture ideal mixing entropy has to be added