Saltpetre (n.) 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..

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