. ON THE CARBONACEOUS PRINCIPLE. 333 



flammable air, and that which had been exposed to heat 

 alone, all other circumstances being similar, evolved nearly 

 one cubical inch and fa both of which were pure hi- 

 drogen. 



in another experiment of a similar kind, in which frag- A similar eat 

 ments of diamonds were used in the quantity of four grains, P enment * 

 the potassium became extremely black from its action upon 

 them during an exposure to heat for three hours, and the 

 diamonds were covered with a grayish crust, and when acted 

 upon by water and dried, were found to have lost about 

 ^•y of a grain in weight. The matter separated by washing, 

 and examined, appeared as a fine powder of a dense black 

 colour. When a surface of platina wire was covered with 

 it, and made to touch another wire in the Voltaic circuit, 

 a brilliant spark with combustion occurred. It burnt, when 

 heated to redness in a green glass tube filled with oxigen gas, 

 and produced carbonic acid by its combustion. 



These general results seem to show, that in plumbago the Piumbaj^ 

 carbonaceous element exists merely in combination with 

 iron, and in a form which may be regarded as approaching 

 to that of a metal in its nature, being conducting in a high 

 degree, opaque, and possessing considerable lustre. 



Charcoal appears to contain a minute quantity of hidro- Charcoal. 

 gen in combination. Possibly likewise, the alkalis and 

 earths produced during its combustion exist in it not fully 

 combined with oxigen ; and according to these ideas, it is 

 a very compounded substance, though in the main it con- 

 sists of the pure carbonaceous element. 



The experiments on the diamond render it extremely Diamond, 

 likely, that it contains oxigen; but the quantity must be 

 exceedingly minute, though probably sufficient to render the 

 compound nonconducting: and if the carbonaceous element 

 in charcoal and the diamond be considered as united to still- 

 less foreign matter in quantity, than in plumbago, which 

 contains about ~ z of iron, the results of their combustion, 

 as examined independently of hygrometrical tests, will not 

 differ perceptibly. 



Whoever considers the difference between iron and steel, Minute differ- 

 in which there does not exist more than ^ of plumbago, c ™**^ c °™" 

 or the difference between the amalgam of ammonium and greatly alter 



< mercury, 



