Soap

(sōp, 20), n. [A-S. sâpe, Icel. sâpa, Sw. såpa, Dan. säbe, L. Ger. sepe, D. zeep, O. H. Ger. seifa, N. H. Ger. seife, Lat. sapo, Gr. σάπων, It. sapone, Sp. xabon, Pg. sabâo, Pr. sabo, Fr. savon; W. sebon, Ir. & Gael. siabunn.] A compound of one or more of the acids obtained from fatty bodies, with alkalies or oxides.

☞ Soaps are commonly either margarates or oleates of potassa or soda, made by boiling some common oil with the lye of wood ashes, and are used in washing and cleansing. Soap is used in medicine as a cathartic.

Castile soap, a hard, mottled kind of soap, made from olive oil and soda. The mottled appearance is given by adding green vitriol and sulphureted ley to it while in a pasty condition. — Insoluble soap, an insoluble compound of a metallic oxide with a fatty substance, not possessing detergent qualities. — Soft soap, a viscid, semi-fluid, potash soap, of a dirty, brownish-yellow color, having an excess of alkali.