ABSTRACT
The chapter evokes some physical-chemical constants the chemist may use to control the purity of the species it has isolated. 1) When it is solid, the crystalline aspect is an important criterium of homogeneity of the sample. The fusion point is also a very important criterium in the same respect as just before. There are several manners to measure the fusion point. The chapter also mentions a method of purification by fusion named the “zone refining” technique The chapter recalls that impurities may modify considerably the values of the melting points. It also recalls that the azeotropic mixtures must receive special theoretical treatment in this case. 2) In the case of liquids, several methodologies may be retained. The determination of the ebullition point and the refractive index is mentioned.
