110 On some new analytical Researches 



hydroo-en in the second case to any other cause than to the 

 supply of oxvg(in to the potassium from the phosphorus ; 

 and the qusnlily of phoaphurettod hydrogen evolved in the 

 first case, is much less than could be expected, if both po- 

 tassium and phosphorus consisted merely of pure combustible 

 matter. 



The phosphoric acid, formed by tlie combustion of phos- 

 phorus, though a crystalline solid, may still contain water. 

 The hydrogen evolved from phosphorus by electricity proves 

 indeed that this must be the case; and though the quantity 

 of hvdrogen and oxygen in phosphorus may be exceedmgly 

 fcrnall, yet they may be sufficient to give it peculiar cha- 

 racters ; and till the basis is obuuncd free, we shall have no 

 knowledge of the properties of the pure phosphoric element. 



V. 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 oxygen in 

 combustion. 



Hence it is evident, thai they must consist principally of 

 the same kind of elementary matter; but minute researches 

 upon their chemical relaiions, when examined by new ana- 

 lytical methods, will, I am inclined tobelieve, show that tlie 

 great difference in their physical properties does not merely 

 depend upon the differences of the mechanical arrangement 

 of their parts, but likewise upon diflerences in their intimate 

 chemical nature. 



1 endeavoured to discover, whether any elastic matter 

 could be obtained from plumbago very intensely ignited by 

 ibe Voltaic battery in a Torricellian vacuum : but though 

 the highest power of the battery of five hundred was en>- 

 ployed, and though the heat was such, as m another expe- 

 riment instantly melted platina wire of -g-Vth of an inch in 

 diameter, yet no appearance of change took place upon the 

 plumbago. Its characters remained wholly unaltered, and 

 no permanent elastic thiid was formed. 



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

 potassium, in a plate glass tube connected with a proper ap- 

 paratus, 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 hydro- 

 gen : no ga« was evolved in either case. There was lio igni- 

 tion 



