The Third Law of Thermodynamics A Critical Assessment

The most important post-Gibbsian addenda alluded to by Lewis and Randall (1923) are introduced in their section entitled The Third Law of Thermodynamics as follows  

Up to this point it has been our purpose to develop as fully as possible the science which may be called classical thermodynamics, and which consists in a study of the consequences and applications of the first and second laws. It has seemed desirable to build broadly upon these two principles, which are universally accepted, before introducing certain other principles of more recent discovery, the validity of which has not yet been so completely demonstrated. 

The third law, associated most prominently with the name of W. H. Nemst, remains to this day the most problematic and controversial of the post-Gibbsian developments. 

The third law is concerned with the nature of entropy (Sidebars 5.10-5.13) and thermodynamic behavior in the limiting approach toward T = OK. Although Joule-Thomson expansion (Section 3.6.3) is a useful refrigeration technique down to about 20K (7J for H2), more specialized cryogenic techniques are required to approach the sub-microkelvin (around 10 6K) domain of extreme low temperatures. The most important such technique, adiabatic demagnetization, is described in Sidebar 5.16. 

However, the spin-disordered state of high 5spin can alternatively be achieved by adding heat to the spin system  

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