86 COMMON SALT. 



Soda like potash is never found in its pure 

 state, but always combined with some acid, 

 indeed it is with difficulty obtained in any 

 other form. 



We purpose here to consider this salt in 

 the three states only in which it exists most 

 abundantly, viz. — ^as common salt, a combi- 

 nation of chlorine and sodium ; common soda, 

 such as is sold in the shops for washing and 

 other purposes; and nitrate of soda: — all of 

 which have an important influence on vegeta- 

 tion. 



In its combinations with other acids this salt 

 is quite unimportant as far as its uses in agri- 

 culture are concerned. 



Common Salt. — The first state of soda that 

 comes under our notice is a compound of chlo- 

 rine gas and sodium, in the proportion of 36 

 atoms of the former to 24 of the latter. It ex- 

 ists abundantly as a native product in many 

 parts of the globe ; but in others it is almost 

 deficient. 



In our own country it forms an immense 

 source of traffic, not only with those places 

 distant from its sources, but also with many 

 European states where it does not so abun- 

 dantly exist. 



There are three sources from which this 

 salt is derived, first as a native rock salt at 

 Northwich in Cheshire, next from the brine 

 spring at Droitwich in Worcestershire, and 

 lastly by evaporating the sea water and thereby 

 obtaining the salt held in solution. 



Some idea may be formed of the immense 



