an operation by which a solid body is reduced into a liquid; or the action of fire or heat on fat and other fusible bodies, which puts their parts into a mutual intestine motion.—The liquefaction of wax, &c., is performed by a moderate heat; that of fat tartar, by the mere moisture of the air. All fats liquefy; sand, mixed with alkalies, becomes liquefied by a reverberatory fire, in the making of glaas. In speaking of metals, instead of liquefaction, we ordinarily use the word fusion.