ON THE CARBONACEOUS PRINCIPLE. 331 



of hidrogen gas; the deficiency in the result, in which 



potassium alone was used, must bo ascribed to the loss of a 



small quantity of metal, which must have been carried off 



in solution in the hidrogen, and perhaps, likewise, to the 



action of the minute quantity of metallic oxides in the plate 



glass. The difference in the quantity of hidrogen given oft* 



in the two results is however too slight, to asciibe it to the 



existence of oxigen in the plumbago. 



- I repeated this experiment several times with like re* The expeii- 



sults, and in two or three instances examined the compound ment repeated. 



formed. It was infusible at a red heat, had the lustre of 



plumbago. It inilamed spontaneously, when exposed to 



air, generated potash, and left a black powdery residuum, 



It effervesced most violently in water, and produced a gas, 



which burnt like pure hidrogen. 



When small pieces of charcoal from the willow, that had Charcoal acted 



been intensely ignited, were acted upon by Voltaic, clectri- u ^ onb y the 

 J w 7 i j . pii e in vacuo. 



city in a 1 orricellian vacuum, every precaution being taken 

 to exclude moisture from the mercury and the charcoal, the 

 results were very diiiercnt from those occurring in the case 

 of plumbago. 



When plumbago was used, after the first spark, whiclj. 

 generally passed through a distance of about one eighth of 

 an inch, there was no continuation of light, without a con.. 

 tact or an approach to the same distance; but from the 

 charcoal a ilame seemed to issue of a most brilliant purple, A , fl 

 and formed, as it were, a conducting chain of light of nearly formed, 

 an inch in length, at the same time that elastic matter was d i rt « 

 rapidly formed, some of which was permanent. After ter evolved, 

 niany unsuccessful trials, I at length succeeded in collecting « 



the quantity of elastic fluid given out by half a grain of 

 charcoal; the process had been continued nearly half an 

 hour. The quantity of gas amounted to nearly an eighth 

 of a cubical inch ; it was iuiiammable by the electric spark 

 with oxigen gas, and four measures of it absorbed three 

 measures of oxigen, and produced one measure and a half 

 of carbonic acid. The charcoal in this experiment had be- 

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

 heated to whiteness, approached to that of plumbago. 



J heated two grains of potassium together with two grains charcoal heat- 



of 



