J4f GASES ABSORBED BY CHARCOAL 



Oxigen gas. three lines in tubes of twelve inches in height. I am cer- 

 tainly not miftaken ; and M M. Rouppe and Van-Norder, 

 who have repeated my experiments in their apparatuses, have 

 obtained the fame refults, and have found, as I did, that, 

 next to hidrogen, oxigen gas is that which is leaft abforbed 

 by charcoal.* 



30th. I muft not pafs over a fingular experiment, the ex- 

 planation of which will alfo be very difficult. 



I examined the abforption which a piece of charcoal, that 

 had remained feven hours in the bright light of the fun, had 

 effected in the fame oxigen gas ; it was only between feven 

 and eight lines, while a fimilar piece, which had been only 

 five hours in the folar light, produced an abforption of ten 

 inches three lines in carbonic acid gas. 



It muft be obferved, that a piece of charcoal expofed to 

 the light of the fun and placed in oxigen gas, produced only 

 an abforption of feven or eight lines, juft like the abforption 

 of a piece which had been expofed to the fun's light, and 

 placed in hidrogen gas, which gave only an abforption of fix 

 lines : and, in this, thefe refults are perfectly conformable to 

 my experiments, made in the year 1783. 



31 ft. This difference of the refults is therefore only owing 

 to the method either of paffing the charcoal under the mercury, 

 or of leaving it in the machine. It appears that, by paffing 

 it through the mercury, the charcoal lofes much of its attrac- 

 tive power, which it retains in the machine. 



Let us endeavour to find whether thefe differences can be 

 accounted tor. 



32d. It might be fuppofed that the red-hot charcoal in- 

 flames the oxigen gas; but fince I do not open the key until 

 fome time after the charcoal has been infer ted, it does not 

 appear to me to be likely that the gas can be inflamed : befides, 

 if this were the cafe, the abforption would be made at once, 

 and it would not require eight days to be complete. 



33d. It might be fuppofed that, in this cafe, the charcoal 

 {applied hidrogen gas, which, mixing with the oxigen gas 

 and producing water, would caufe the abforption : but during 

 the whole experiment there was not the fmalleft drop of water 

 -perceived in the tube. 



* Ann. de Chimie, 

 4 34th. 



