

•N THE CARBONACEOUS PJII\CIP£E. 



Plumbago, 

 rh^rcoal, and 



diamond, 



consist princi- 

 pally or the 

 same dement, 



butvith che- 

 mical difi'er- 

 encies. . ' 



Plumbago 

 acted upon by 

 the pile m 



>iiCUO. 



TTeated with 



ium in 



kidrojren jras. 



5. On the States of the carbonaceous Principle in Plumbago^ 

 Charcoal, and the Diamond. 



The accurate researches of Messrs. Allen and Pepys have 

 distinctly proved, that plumbago, charcoal, and the diamond 

 produce very nearly the same quantities of carbonic acid, 

 and absorb very nearly the same quantities of oxigen ic 

 combustion. 



Hence it is evident, that they must consist principally of 

 the same kind of elementary matter; but minute researches 

 upon their chemical relations, .when examined by new ana- 

 lytical methods, will, I am inclined to believe, show, that 

 the great difference in their physical properties does not 

 merely depend upon the differences of the mechanical, ar- 

 rangement of their parts, but likewise upou differences in 

 their intimate chemical nature. 



I endeavoured to discover, whether any elastic matter 

 could be obtained from plumbago very intensely ignited by 

 the Voltaic battery in a Torricellian vacuum: but though 

 ihc highest power of the battery of five hundred was em- 

 ployed, and though the heat was such, as in another ex- 

 periment instantly melted platina wire of -^th of an inch 

 in diameter, yet no appearance of change took place upon 

 the plumbago. Its characters remained wholly unaltered, 

 and no permanent elastic fluid was formed. 



I heated one grain of plumbago, with twice its weight of 

 potassium, in a plate glass tube connected with a proper 

 apparatus, and I heated an equal quantity of potassium 

 .alone in a tube of the same kind, for an equal length of 

 time, namely, eight minutes. Both tubes were filled with 

 hidrogen : no gas was evolved in cither case. There was no 

 ignition in the tube containing the plumbago, but it seemed 

 gradually to combine with the potassium. The two results 

 were exposed to the action of water ; the result from the 

 plumbago acted upon that fluid with as much energy as the 

 other result, and the two volumes of elastic fluids were 1*8 

 cubical inch and 1*9 cubical inch; and both gave the 

 same diminution by detonation with oxigen, as pure hi- 

 drogen. Two grains of potassium, by acting upon water, 

 would have produced two cubical inches and one eighth 





