AGRICULTURE WITH CHEMISTRY. 49 



ALKALINE SALTS 



Are fixed, or volatile. The fixed are obtained by 

 the combustion of marine and terrene plants. Mineral 

 alkali is also to be procured from muriat of soda, or sea 

 salt. The volatile is obtained from urine — animal mat- 

 ter — fossile coal — soot — and other substances. Alkaline 

 salts combine with acids, forming neutral salts; with 

 animal fat, antl oil, and vegetable oils, they form soaj), 

 or a saponaceous matter, diffusible in water. Alkaline 

 salts av5l upon and destroy the continuity of the parts of 

 animal and vegetable substances : they a£l: mo^t power- 

 fully on the latter, when oxygenated, forming therewith 

 saline compounds, which, in a very high degree, pro- 

 mote vegetation. 



Oxygenated vegetable matter, and oxygenated peat, 

 M hen decomposed, ;'.nd renclci-cd solulile by alkaline salts, 

 assume a brownish red colour, and are tasteless : hence 

 the alkali must enter into combination, and be neu- 

 tralized by an acid or acicis. These will be found to 



G be 



