chapter  7
Solid-Liquid Extraction
Pages 7

Leaching or solid-liquid extraction are terms used to describe the extraction of soluble constituents from a solid or semisolid by means of suitable solvents. The process, which is used domestically whenever tea or coffee is made, is an important stage in the production of many fine chemicals found naturally in animal and vegetable tissue. Examples are found in the extraction of fixed oils from seeds, this method offering an alternative to mechanical expression, in the preparation of alkaloids, such as strychnine from Nux vomica beans or quinine from Cinchona bark, and in the isolation of enzymes, such as renin, and hormones, such as insulin, from animal sources. In the past, a wider impor-tance attended the process because the products of simple extraction proce-dures, known as Galenicals, formed the major part of the ingredients used to fulfill a doctor's prescription.