AGRICULTURE WITH CHEMISTRY. 55 



On iron the changes are produced by the alternate adlion 

 of inflammable matter, and pure air or oxygen : in the 

 former case fixable air is disengaged ; in the latter, at- 

 mospheric air is separated, or decomposed, by the abstrac- 

 tion from it of pure air. Both the azotic or phlogisti- 

 cated air, the other component part of atmospheric air, 

 and fixable air, promote the growth of plants. 



VITRIOLIC ACID. 



This acid, in the new nomenclature, is called by the 

 French chemists the sulphuric acid ; a name much more 

 descriptive of its origin than that generally used. 



All acids, in the new nomenclature, are named from 

 the peculiar bases or substances of which they are formed, 

 by the combination of pure air, or oxygen ; the presence 

 of which in all cases is necessary to constitute an acid. 

 This process, under the head of oxygenation, has been 

 frequently resorted to, and Avhich, together with the 

 insoluble saline compounds formed by the developemcnt 



of 



