Saltpetre

Nitre, or nitrate of pota a, is composed of 54 parts nitric acid and 48 parts of pota a. It is spontaneously generated in the soil, and is a nece ary ingredient of powder. It has occasionally been produced artificially in nitre-beds , formed of a mixture of calcareous soil with animal matter; in these, nitrate of lime is slowly formed, which is extracted by lixiviation and carbonate of potash added to the solution, which gives rise to the formation of nitrate of pota a and carbonate of lime; the latter is precipitated; the former remains in solution and is obtained in crystals by evaporation. Its great use is in the manufacture of gunpowder, and in the production of nitric acid. See Gunpowder .