Mother liquor

As a mother liquor, the liquid is called, from which the chemical purification by recrystallization a desired material has deposited in the form of crystals. The separation of the crystals from the mother liquor can be carried out by decantation or filtration.

Therefore mother liquors contain residues of the crystallized substance and the original impurities that can often be recovered in a subsequent step from these solutions. From the mother liquor, after evaporation of a part of the solvent followed by cooling often also a second crystal fraction of the desired substance are obtained. This second crystal fraction is usually not as " clean" ( chemically homogeneous), as the first crystal fraction.

In industrial processes resulting mother liquors are recycled times in order to optimize the yields.