462 



SODIUM. 



from the existence everywhere of a soluble compound of sodium, 

 its chloride, the sources of that element are the more accessible, 

 if not the most abundant. 



The anhydrous protoxide of sodium and the peroxide are pre- 

 pared in the same manner as the corresponding oxides of potas- 

 sium, which they greatly resemble in properties. The composi- 

 tion of the peroxide of sodium, however, is different, being 

 expressed by the formula 2Na + 3O (Thenard). It is supposed 

 by M. Millon to be Na + 2O. 



COMPOUNDS OF SODIUM. 



Soda; Na O ; 391 or 31.31. A solution of soda is obtained 

 by decomposing the crystallized carbonate of soda, dissolved in 

 4 or 5 times its weight of water, by means of half its weight 

 of hydrate of lime ; the same points being attended to as in the 

 preparation of potash. A preference is given to this alkali 

 from its cheapness, for most manufacturing purposes, and in 

 the laboratory it may generally be substituted for potash, where 

 a caustic alkali is required. On the large scale it is prepared 

 from salts of soda, a carbonate containing chloride of sodium 

 and sulphate of soda. The solution of soda is purified from 

 these salts by concentrating it considerably, upon which the 

 foreign salts cease to be soluble in the liquid and precipitate 

 (Mr. W. Blyth). 



The following table, constructed by Dr. Dalton, exhibits the 

 quantity of caustic soda in solutions of different densities : 



SOLUTION OF CAUSTIC SODA. 



The solid hydrate of soda is obtained by evaporating a solu- 

 tion of soda, precisely in the same manner as the corresponding 

 preparation of potash. It is soluble in all proportions in water 

 and alcohol. 



Soda is distinguished from potash and other bases by several 



