base, in geometry. See Base.

Base, in chemistry, any body which is dissolved by another body, which it receives and fixes, and with which it forms a compound, may be called the basis of that compound. Thus, for example, the bases of neutral salts are the alkaline, earthy, and metallic matters which are saturated by the several acids, and form with them these neutral salts. In this sense it is that these neutral salts are called salts with earthy bases, salts with alkaline bases, salts with metallic bases: also the appellations basis of alum, basis of nitre, basis of Glauber's salt, basis of vitriol, &c. signify the argillaceous earth, which, with the vitriolic acid, forms alum; the vegetable alkali, which, with the nitrous acid, forms nitre; the mineral alkali, which, with the vitriolic acid, forms Glauber's salt; and the metal which, with the vitriolic acid, forms a vitriol; because these substances are supposed to be fixed, unactive, and only yielding to the action of the acids, which they fix, and to which they give a body and consistence.

among physicians, denotes the principal ingredients in compound medicines.