Similar components A necessary and sufficient condition for SI solutions

2 Similar components A necessary and sufficient condition for SI solutions 

In the previous section, we showed that for a mixture of very similar (in the sense defined there) components, the chemical potential of each component i has the form  

Experimentally, it had been known long ago that many mixtures are SI although the two (or more) components are far from being very similar in the sense of section 5.2.1. 

We shall now show that indeed a much weaker condition is required for SI, which turns out to be both a sufficient and a necessary condition. 

Clearly, (5.35) and (5.36) are equivalent conditions for SI solutions, in the sense that each one follows from the other. 

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