112 On some new dnalytical Researches 



become harder at the point, and its lustre, where it had been 

 heated to whiteness, approached to that of phnnbaeo. 



I heated two grains of potassium together with two grains 

 of charcoal, for five minutes; and to estiina:e the effecta of 

 the metallic oxides and potash in the green glass lube, I 

 made a comparative experiment, as in the case of plumbago ; 

 but there was n.) proof of any oxvgen being furnished to the 

 potassiuni from the charcoal in the proceS's, for the com- 

 pound acted upon water with great energv, and produced a 

 quantity of inHanimable gas, only inferior by one twelfih to 

 that producetl bv the potassium, which had not been com- 

 bined with charcoal, and which gave the same diminution 

 by detonation with oxvgen ; and the slight dHTerence may 

 be well ascribed to the inHuence of foreign matters in the 

 charcoal. There was no ignition in the process, and no 

 gas was evolved. 



~ The compound produced in other experiments of this kind 

 was examined. It is a conductor of electricity, is of a dense 

 black, inflames sjiontaneouslvj and burns with a deep red 

 light in the atmosphere*. 



The non-conducting nature of the diamond, and its infusi- 

 bilitv, rendered it impossible to act upon it bv Voltaic clec- 

 Iricily ; ^i^d the only new agents which seemed to ofler any 

 means of decomposing it, were the metals of the alkalies. 



When a dia.nond is heated in a green glass tube with po- 

 tassium, there is no ela.slic fluid given out, and no intensity 

 of action ; but the diamond soon blackens, and scales seem 

 to detach themselves from it ; and these scales, when ex- 

 amined in the magnifier, are gray externally, and of the 

 colour of plumbago internally, as if they consisted of plum- 

 bago covered by the gray oxide of potassium. 



In heating together three grains of diamonds in powder, 

 and two grains of potassium, for an hour in a small retort 

 of plate glass filled with hydrogen, and making the com- 

 parative trial with two grains of potassium heated in a simi- 

 lar apparatus, without any diamonds, I found that the po- 

 tassium which had been heated with the diamonds, produced, 

 by its action upon water, one cubical inch and tV^* "^ 'i^' 

 flammable air, and that which had been exposed to heat 

 alone, all other circumstances being similar, evolved nearly 

 one cubical inch and j-V^"'^* both of which were pure hy- 

 drogen. 



* In the Bakerian Lecture for 1S07, I have mentioned the decomposition 

 of carbonic acid by potassium, which takes place with inflammation. Ifllje 

 potnssium is in excess in this expeiipieut, the same pyrophorus as that dc- 

 •cribcU above is foriae^. 



It 



