Second Law The Analytical Statement

Once we understand the concept of a reversible heat engine, we are ready to develop the analytical statement of the second law. This is carried out with the use of the ensuing four Propositions discussed briefly here (for an in depth presentation see Denbigh p.26)  

For any natural (spontaneous) process, the total entropy change (45, ) equal to  

This expression represents the analytical statement of the second law. 

---