104 NITRATE OF SODA. 



known that sulphuric acid poured on salt expels mu- 

 riatic acid, whilst, on the other hand, there are sub- 

 stances which can take away the acid and leave caus- 

 tic soda. It is now known that dry salt contains 

 nothing but chlorine and sodium ; and when it is de- 

 composed by sulphuric acid, or in any other way, the 

 muriatic acid and soda evolved were not contained 

 in the salt, but are formed by the decomposition of 

 a portion of water, the oxygen of which unites with 

 the sodium to form soda, whilst the hydrogen com- 

 bines with the chlorine to form muriatic acid. Hence, 

 though strictly speaking common salt is a chloride 

 of sodium, yet for practical purposes it may be con- 

 sidered as a muriate of soda; because whatever 

 change it undergoes, or in whatever manner it is de- 

 composed, soda and muriatic acid are given out just 

 as if they were really the components of salt. Soda 

 is an oxide of sodium. 



217. The only other compound of soda, which 

 occurs native in any quantity, is the nitrate or cubic 

 nitre, as it is commonly called. It is found native 

 in large quantities in certain parts of South America, 

 and is used to a considerable extent as a manure. 

 When it was first brought over to this country, some 

 few years ago, it was proposed to substitute it for the 

 nitrate of potash in the manufacture of gunpowder, 

 and in the preparation of nitric acid. It was, how- 

 ever, found that it possessed the property of attract- 

 ing moisture from the air ; and hence, being always 

 more or less damp, it could not be used by the gun- 



