KO,CO, CaO,NO. = CaO,CO, KO,N05 The clear liquor is then evaporated and crystallized. It has been found that the earth in which niter has once been formed furnishes fresh niter more readily than on the first occasion. Care is taken that the niter plantations, as they are termed, shall rest upon an impervious flooring of clay, so that the liquid which drains away'from them may be col lected and preserved."—Miller's Elements of Chemistry, 2d ed. vol. ii. p. 359.
Niter does not occur in any living members of the animal kingdom, but it is found in the juices of various plants, amongst which may be named the sunflower, nettle, goose-foot, borage, tobacco, barley, etc.
All the niter used in this country comes from the East Indies. The common varieties, which have a dirty yellowish appearance, are termed rough or crude saltpeter, while the purer kinds are called East India refined. The purification or refining of niter is effected by dissolving it in water, boiling the solution, removing the scum, straining it while hot, and setting it aside to Crystallize. The most common impurities are sulphate of potash. chlorides of sodium and potassium, and nitrate of lime. Chloride of barium will detect the first Of these lithpurities; nitrate of silver the of ammonia the third.
Niter is employed in the manufacture of sulphuric acid, in the preparation of nitric acid, as an oxidizing agent in numerous chemical processes, as an ingredient of fireworks, and especially in the manufacture of gunpowder. It is extensively used in medicine. In moderate doses (from ten grains to a scruple) it acts as a refrigerant, diuretic, and diaphoretic, and hence its use is indicated when we wish to diminish abnormal heat, and to reduce the action of the pulse, as in febrile disorders and hemorrhages. In acute
rheumatism it is given in large doses with great benefit. Sonia physicians prescribe as much as one, two, or three ounces, largely diluted with water, to be given in the course of 20 hours; but as in several cases a single ounce has proved fatal in a few hours, the effects of such large doses should be carefully watched. It is a popular remedy in sore throat, either in the form of niter balls, or powdered and mixed with white sugar. In either case the remedy should be retained in the mouth till it melts, and the saliva impregnated with it gently swallowed. The inhalation of the fumes produced by the ignition of touch-paper often gives speedy relief in cases of spasmodic asthma.
Nitrate of potash is sometimes called prismatic niter or potash saltpeter, to distinguish it from nitrate of soda, which is known in commerce as cubic niter or soda saltpeter.
Cubic niter, or nitrate of soda (NaO,N0,,), occurs abundantly on the surface of the soil in Chili and Peru. It derives its name from its crystallizing in cube-like rhombohedrons. In most of its properties it resembles ordinary inter, but in consequence of its greater deliquescence it cannot be substituted for that salt in the preparation of gunpowder. Being considerably cheaper than the potash-salt, cubic niter is often substituted for it in the manufacture of nitric and sulphuric acids; and it is used in agriculture as a top dressing for wheat And oats. In several experiments it has been found that one cwt. per acre has produced an increase of 12 bushels in the wheat crop, and of 4 or 5 sacks in the oat crop