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nitre:see potassium nitratepotassium nitrate,
chemical compound, KNO3, occurring as colorless, prismatic crystals or as a white powder; it is found pure in nature as the mineral saltpeter, or niter. (The name saltpeter is also applied to sodium nitrate, although less frequently.
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any of-the nitrates (nitric acid salts) of alkali and earth metals and ammonium. In nature, niters are formed during the decomposition of various organic radicals upon the action of nitrifying bacteria. From the mid-14th century, the term “saltpeter” was applied to potassium nitrate (KNO3)—the main constituent of black gunpowder.
KNO3 was obtained from niter piles—agglomerates of manure mixed with limestone, marl, and building debris that were placed between layers of brushwood or hay. Decomposition of this mixture yielded ammonia, which, during nitrification (aided by bacteria), was converted first to nitrous and then to nitric acid. Interaction of the nitric acid with CaCo3 gave Ca(NO3)2, which was then leached with water. The addition of wood ash, composed mainly of K2CO3, induced the precipitation of CaCO3 and the formation of a KNO3 solution. This method was used until 1854, when the German chemist C. Nöllner began producing KNO3 with the reaction KCl + NaNo3 = KNO3 + NaCl in solution. The raw materials here were natural Chile saltpeter (NaNO3) and KC1, which was obtained from natural potassium salts. This method has gradually replaced the previous one. Niters are primarily used as nitrogenous fertilizers.
S. A. POGODIN