292
ELEMENTS OF MATERIA MEDICA
History. —At what time this salt became known is difficult now todetermine. As it is found in various parts of the East, on the surface ofthe earth, it appears probable that it must have been known at a veryearly period. Furthermore, if the Chinese and Hindoos were acquainted
with the art of making gunpowder and fireworks at a very early period
of history, they must have employed, and, therefore, been acquainted with,nitre. Geber, {Invention of Verity) however, is the first who distinctlymentions it. But the terms neter of the Old Testament ( Prov. ch. xxv. 20 ;Jer. ch.ii. 22), translated nitre, — vhpov of Herodotus {Euterpe, lxxxvii.)and Theophrastus {De Igne) —and nitrum, of Pliny {Hist. Nat. xxx. i.),appear to have been applied either partially or exclusively to natron (ses-qui-carbonate of soda.) (See Beckman’s History of Inventions and Dis-coveries, vol. iv.) The word saltpetre, usually applied to nitre, is evidentlyderived from salpetrce, literally signifying rock salt.
Natural History . —This salt occurs in both kingdoms of nature.
{a.) In the inorganized kingdom,. —In the East Indies, Egypt, Persia ,Spain , and other parts of the world, large quantities of nitre are found inthe soil. It would appear to be formed below, and to be brought to thesurface of the soil by efflorescence. Some have thought that the nitricacid of the salt was formed by the union of the nitrogen and oxygen ofthe atmosphere, while others have supposed the presence of animal mat-ters necessary to yield, by their decomposition, nitrogen. In someinstances the latter opinion is probably correct: but it does not invariablyhold good, for in a nitre cave at Ceylon, Dr. Davy {Account of the Inte-rior of Ceylon) found nitre without any animal matter. The potash ofthe nitrate is in most cases easily accounted for, being found in some ofthe constituents of the soil, namely, feldspar and mica.
(6.) In the organized kingdom. This salt has been found in variousplants, as in the roots of Cissampelos Pareira, Geum urbanum, &c. (De-candolle, Phys. Veget. p. 387.)
Preparation. —The nitrate of potash consumed in this country isimported from India , where it is obtained from natural sources. In someparts of Europe it is procured artificially.
1. From natural sources. —The district of Tirhut, in Bengal, is moreproductive of nitre than any other place in India . It is most abundantin those parts containing a redundancy of carbonate of lime. An averagesample of the soil analyzed by Mr. Stevenson {Journ. of the AsiaticSociety of Bengal, vol. ii. p. 23) gave the following composition:
Matter insoluble in three Mineral Acids . . Silex
50-0
44-3
Carbonate of Lime .
Matter soluble in ditto
Nitrate of Potash
Matter soluble in Water
lOO'O
“ In the month of November the leonahs, or native manufacturers ofsaltpetre, commence their operations, by scraping off the surface from oldmud heaps, mud buildings, waste grounds, &c. where the saltpetre hasdeveloped itself in a thin white efflorescence, resembling frost rind. Thissaline earth being collected at the factories, the operator first subjects it