saltpeter

{ } n. [ F. salpêtre, NL. sal petrae, literally, rock salt, or stone salt; so called because it exudes from rocks or walls. See Salt, and Petrify. ] (Chem.) Potassium nitrate; niter; a white crystalline substance, KNO3, having a cooling saline taste, obtained by leaching from certain soils in which it is produced by the process of nitrification (see Nitrification, 2). It is a strong oxidizer, is the chief constituent of gunpowder, and is also used as an antiseptic in curing meat, and in medicine as a diuretic, diaphoretic, and refrigerant. [ 1913 Webster ]

Chili salpeter (Chem.), sodium nitrate (distinguished from potassium nitrate, or true salpeter), a white crystalline substance, NaNO3, having a cooling, saline, slightly bitter taste. It is obtained by leaching the soil of the rainless districts of Chili and Peru. It is deliquescent and cannot be used in gunpowder, but is employed in the production of nitric acid. Called also cubic niter. --
Saltpeter acid (Chem.), nitric acid; -- sometimes so called because made from saltpeter. [ 1913 Webster ]