Word Study
saltpetre
CIDE DICTIONARY
saltpetre, 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.].
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]
OXFORD DICTIONARY
saltpetre, n. (US saltpeter) potassium nitrate, a white crystalline salty substance used in preserving meat and as a constituent of gunpowder.
Etymology
ME f. OF salpetre f. med.L salpetra prob. for sal petrae (unrecorded) salt of rock (i.e. found as an incrustation): assim. to SALT
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