COMPOSITIONS OF PLANTS. 



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cannot be dissolved but by a red heat with alkalies. We 

 shall not, therefore, be too hasty, if we suspect that plants 

 form siliceous earth, from carbon and hydrogen, especially as 

 the diamond, which is the most perfect of the gems, is 

 almost entirely composed of carbon and hydrogen. Lime, 

 also, as it is a principal product of the animal kingdom, and 

 is found almost every where along with azote, is probably a 

 compound of this latter body with carbon. 



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360. 



With respect to the metals which we find in the ashes of 

 plants, they may be reduced, so far as is known to us, to the 

 following, namely, iron, manganese and copper. The last of 

 these is found in the tubercles of the Scitamineae. Iron is 

 found in the ashes of almost all plants, and frequently united 

 with oxide of manganese. 



Although we know not the elementary bodies from which 

 metals are formed, it is very probable according to Do- 

 bereiner''s experiments, that carbon, in union with hydrogen 

 and azote, suffers a change during the process of vegetation, 

 which assimilates it to a metallic nature ; perhaps this change 

 has an influence upon the colours of blossoms, and by the 

 power of heat, the metal in the organic body is transformed 

 to a metallic oxyde. 



361. 



When we proceed to the consideration of the more remote 

 constituents, a wide field is opened to conjecture. Sulphur, 

 phosphorus, the elementary matter of cyanogen, the fundamen- 

 tal principles of halogen, and iodine are more or less related 

 substances, which, by their great inflammability, and tendency 

 to assume the gaseous form, attract oxygen from air and wa- 

 ter, and thus form peculiar acids. 



Sulphur exists in albumen, and in other vegetable juices ; 

 and sulphuric acid salts are found in the ashes of almost all 

 plants. Albumen also contains phosphorus, and phosphorated 

 lime, and salts compounded with the same acid are produced 

 in the juices of many plants. The phosphoric Ught of putrid 



