NITRATE OP POTASH. 101 



206. One of the most important of the salts of 

 potash, is the nitrate, or, as it is commonly called, 

 saltpetre, or petre, which is found native in many 

 places as a white powdery matter on the surface of 

 the ground, and is procured pure by washing the 

 earth, and evaporating the solution of nitre thus 

 obtained. 



207. Nitre is a perfectly neutral salt, and is in 

 that respect very different from the carbonate of 

 potash, which, although far less caustic than pure 

 potash, has still very considerable caustic powers, in 

 consequence of which it is so commonly used in 

 washing, and for other household purposes. Car- 

 bonic acid, in combining with the alkalies, does not 

 seem able to neutralize them, or destroy their alka- 

 line powers so completely as most other acids can ; 

 and therefore it must be remembered that the carbon- 

 ates of the alkalies still possess some of the powers 

 of the alkalies themselves. The other compounds 

 formed by the alkalies with the more powerful acids 

 are quite neutral, and in them no traces of the alka- 

 line nature of the bases can be found. 



208. One of the principal uses of nitre is in the 

 manufacture of gunpowder, which consists of nitre, 

 charcoal, and sulphur, finely powdered, and very care- 

 fully mixed together. The chemical action which 

 takes place during the burning or explosioa of gun- 

 powder is very simple. The nitre consists of potash 

 and nitric acid, the latter substance contains a large 

 quantity of oxygen, combined by a comparatively 



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