ABSTRACT
Two methods are studied; fractionated dissolution and sublimation. It is recalled that the goal of fractionated dissolution is to extract one or several constituents from the solid mixture quantitatively. One operation with one solvent may suffice to be successful, but this case is rare. It is necessary to carry out several successive extractions with one or several solvents. These results are discussed with the help of some considerations on the part played by the solvents. An interesting result of this study is the following; for the same volume of solvent, the yield is better when this volume is fractionated. It is also discussed as the part played by their relative permittivity. From the technical standpoint, two processes are retained. Two suitable apparatuses of this kind, those of Soxhlet and Kumagawa, are described. The principle of sublimation is recalled. It is also recalled that this method is very convenient. Unfortunately, it can only be employed to separate volatile substances from non-volatile impurities.
