ABSTRACT
The principle of this group of methods is the following: it is to reduce a liquid phase into its constituents by provoking the apparition of a solid phase in the bulk solution. Let us consider a constituent dissolved in any liquid phase. This phase is homogeneous when its concentration C is lower than its solubility S (in the liquid phase). Otherwise, there is a rupture of the phase. It can be provoked either by increasing C or by lowering S. Hence, there is precipitation. A separation is also possible by fractioned crystallization. The methods which are discussed in the chapter are those founded on the increase of augmentation by eliminating partially or wholly the solvent; the phenomenon of precipitation which can be induced by a difference of temperature in addition to another solvent or by salting out crystallization which can be defined as the sudden spontaneous apparition of a solid body in the bulk solution. In favorable cases, the body which crystallizes is single and otherwise, there is the formation of mixed crystals. Then, the crystallization phenomena may become complicated. In this chapter, the isolation by filtering membranes is also discussed.
