Experiments on Charcoal. 



69 



announces *, that, the temperature and prefture being equal, 

 atmofpheric air, hydrogen and carbonic acid gas, when moift 

 aflecT the hair hygrometer in the fame manner; but as this 

 inftrument indicates only the degree of faturation, and not the 

 quantity of water, we thought it our duty to make fome ex- 

 periments for the purpofe of afcertaining this quantity. 



The property which concrete muriate of lime has to take 

 moift ure from the gafes without altering them, induced us 

 to make choice of it a:s the means of deliccation. 



We made ufe of the apparatus generally employed. It 

 confifts of a glafs tube containing the concrete muriate of 

 lime, the weight of which is known, and through which the 

 gas is made to pafs. In order to be certain of their complete 

 faturation, we made them pafs through ajar filled with water, 

 and placed immediately before the muriate of lime, the tem- 

 perature of which was the fame as that of the atmofphere 

 and of the gafes. It was always 12 or 13 degrees of the cen- 

 tigrade thermometer, and the preffure from 762 to 765 mil- 

 limetres: the other circumftances were alfo as equal as pof- 

 fible. 



The following is a table of the deficcations which we made; 



The carbonic acid, pairing through the flafk of water de- 

 ft ined to moiften it as much as poflible, would have been 

 there diflblved ; but we had previoufly faturated it, fo that 

 there really patted upon the muriate of lime as much of that 

 gas as of the others. 



It is here feen that the quantities of water depofited by 

 each kind of gas were nearly the fame, and the differences 

 can be afcribed only to the unavoidable imperfection of the 

 procefs. Thus it is certain that equal volumes of very dif- 

 ferent gafes depofit the fame quantity of water. 



It remained to know whether the quantities of water 

 which cannot be taken from gafes by deliccation are equal ; 

 but it was almoft impoifible to alcertain this point by a 

 * EJfai fur rHygrometric. chap. ix. of the fecond effay. 



E 3 direct 



