46

NITHATE OF POTASH.

which, although far less caustic than pure potash, hasstill very considerable caustic powers, in consequence ofwhich it is so commonly used in washing, and for otherhousehold purposes. Carbonic acid, in combining withthe alkalies, does not seem able to neutralise them, ordestroy their caustic powers so completely as it can mostother bases; and therefore it must be remembered thatthe carbonates of the alkalies still possess some of thepowers of the alkalies themselves. The other com-pounds formed by the alkalies with the more powerfulacids are quite neutral, and in them no traces of thecaustic nature of the bases can be found

135. One of the principal uses of nitre is in the manu-facture of gunpowder, which consists of nitre, charcoal,and sulphur, finely powdered, and very carefully mixedtogether. The chemical action which takes place duringthe burning or explosion of gunpowder is very simple.The nitre consists of potash and nitric acid,—a substancecontaining a very large quantity of oxygen, combinedby a comparatively weak attraction with a portion ofnitrogen. The finely-powdered charcoal has a verystrong attraction for oxygen, and when sufficientlyheated is able to decompose the nitre, seizing upon theoxygen of the nitric acid, and forming carbonic acid, asmall portion of which combines with the potash of thenitrate, and forms carbonate of potash.

136. The use of the sulphur in gunpowder is similarto its use in the lighting of a common sulphur match ;it very easily catches fire, and the flame thus produced