GASES ABSORBED BY CHARCOAL. 1^ 



fuppofed, on the contrary, to add a confiderable quantity of 

 it to fetid ulcers, and carries off their fetidity as well as 

 charcoal.* 



Water may fometimes be ufed in the Inftrument infiead of 

 Mercury, 



42d. Although, in the courfe of thefe experiments, I have Coloured water 

 conftantly employed mercury, in fome experiments a coloured ^fuSured w 

 water may be ufed with advantage, iince it is better feen in mercury in the 

 the tube ; but this cannot be ufed when the gafes which are machine, 

 abforbed by water are examined, nor with the carbonic acid 

 and the other acid gafes which are much abforbed : then it is 

 necelTary to change the tube, and to fubfiitute one which, 

 infiead of eighteen inches, is at leaft thirty-fix in height; 

 without which it will be entirely filled. 



43d. It was on atmofpheric air -taken in my room with the 

 windows open, that I experimented with coloured water. 

 The charcoal produced an abforption of ten inches and a half. 

 It has been feen, that, with the mercurial apparatus, I had 

 had an abforption of eight inches fome lines. 



The preflure of the atmofphere i*n the water therefore aug- The preflure of 

 mented the abforption, which ufually takes place with the th i atmofphere 

 • , t i «• A-ju. • -l r r , affefts the re- 



mercury, by two inches and a halt; that is to lay, one-fourth f u i ts . 



of the height. 



44th. I fhould obferve, that very frequently the fmall dif- 

 ferences of one or two lines obferved in the abforptions of 

 the fame quality of -air or of gas, are owing to the variations 

 of the atmofphere, which I afcertained by comparing the 

 height of the barometer during the experiment. 



The Pieces of Charcoal ufed in thefe Experiments, acquire Weight. 



45th. After the experiments, all the pieces of charcoal The charcoal 

 employed had acquired greater weight: this augmentation f^JJJJ* ™ ei ^ 

 was from half a grain to two grains, and appears to be de-mentsj 

 pendent on the greater abforption. 



46th. I took four pieces of charcoal which had been ufed 

 in the experiments made with atmofpheric air, which, among 

 them, had acquired four grains in weight: I paffed them 



* See the notes of M. Odier to Beddoes's memoir. Bibl. Brit. 

 Vol. VI. p. 359. 



Vol. X. — January, 180j. C tinder 



