CHILE SALTPETRE, or CUBIC NITRE, is nitrate of sodium, Nals10,, which, however, is not really cubic, but crystallizes in very obtuse angled rhombohedra. It is found in beds in the rainless district of Tarapaca, in Chile, where it occurs sometimes of great purity, but is gen-, erally mixed with other salts (one of which is iodate of sodium), and with sand and clay. These deposits cover more or less completely an area of more than 600 square miles. From the mines it is brought down by rail to the coast, and it is there transferred to ships, origi nally by means of rafts formed of inflated skins. The name of Chile saltpetre is a blunder, When, the first cargo was taken to Liverpool, about 1830, its character was . not known, aria as it could not find a purchaser it was finally thrown overboard. The next cargo went to France, where its value was recognized, and ultimately quantities were brought to England. The de mand for it has gone on steadily increasing. It is used either in mixed artificial manures, or alone as a dressing for grass, the bulk of which it is said to increase. It was anticipated that
it might be used for making gunpowder, but the deliquescence of the salt has been found an insurmountable difficulty. It is, however, transformed into nitre by double decomposition with chloride of potassium, and large quantities are imported into Strassfurt, in Germany, for this purpose. It is, besides, substituted, when ever practicable, for nitrate of potassium as a source of nitric acid. The sole drawback to its general use for this purpose is the presence of chlorides, which, giving off hydrochloric acid, render the nitric acid impure. Of late the in dustry at Tarapaca has been greatly developed. The crude salt or it is called locally, is broken up and the nitrate concentrated by lixiviation with steam and boiling water. The liquor flows continuously from one tank to another gathering more and more of the salt till it has gained the desired strength, and it is then allowed to cool, and the nitrate crystallizes out. From the mother liquor, the world's sup ply of iodine is obtained.