entitled Experiments on Charcoal.. 2jf 



by direct experinlents, which he made known when at Paris, 

 and which are already old; and Priedley announced, that all 

 gales dilfolvcd the fame quantity of ethereal gas, except a 

 iinail difference exhibited by the carbonic acid, which may 

 be eafilv accounted for. 



If the experiments defcribed by Clement and Deforme 

 had been exact, they would have found in a cubic foot of fa- 

 turated atmofphei ic air, at nearly 7 degrees of the thermo- 

 meter*, the fame quantity which they obtained at 1% or 13 

 degrees of the thermometer, 



The elaflic vapour of water has a fpecific gravity, which is 

 to that of air, M the fame degree of compreifion and tempe- 

 rature, as jo to 14 ; but', befides this, there is, in fome gafeous 

 fubfhmces, water combined and more conde'nfed, which has 

 no influence on hygrometric phsenomena ; a difl inction which 

 I indicated in the Ann ales do Chim'ie. by announcing that I 

 mould treat this object in another place, and with the ne- 

 cclTary details. 



It is this combined water which is more or lefs wanting in 

 natural carbonate of barvtes, as has been very properly re- 

 marked long ago by Withering: hence it happens that the 

 acid of this carbonate cannot be difengaged by heat, though 

 it may be d i fen gao-ed from artificial carbonate, which has 

 retained enough of water to give fome of it to the carbonic 

 acid ; but, by employing very dilute nitric acid, the carbonic 

 acid is difengaged from the former as well as the latter, as 

 has been alio remarked by Withering. 



Prieitley has fhown, that, by making the fleam, of water 

 (io. pais upon native carbonate, carbonic acid is eafiiv obtained 

 from it : he juftly afcribes the effect to the part which the 

 carbonic acid ought to take up : he made experiments to de- 

 termine the quantity of it, and though the means Teem ex- 

 act, his remits appear to me exaggerated. 



It is only by this water that we can explain the quantity 

 of hydrogen gas which is obtained by fubjecling carbonic 

 acid to the action of the electric fpark, as done by Dr. Pnelt- 

 fey, Van Marum, Monge and Henry, without decomposing 

 the carbonic acid. 



It is not the hygrometric water which experiences this 

 decompofition, or it form's only a very fmall part of it; for 

 the quantity of hydrogen gas is too confidtrabl.e, and Henry 

 made the experiment with very dry carbonic acid. 

 . C. Clement and Deforme, who pronounce with fo much, 

 confidence that I arri wrong, and who did not deign to wait 



* We fuppofe Rcaiimuf's thermometer is meant.— ^-Edit. 



VoifcvXKI.No, 5u T M 



