\Salt`pe"ter\, Saltpetre \Salt`pe"tre\,, n. [F.
salp[^e]tre, 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.
{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.