C0M3USTI0N OF CHARCOAL A^D OF HIDROGEN. ] (J? 



that of Volta's eudiometer. This comparison led me to, 

 several n%w observations on the use of this instrument. 



fn the trial with hidrosulphuret I followed nearly the pro- 

 cess of Marty. 1 shall only observe, that I coated with suet 

 and sana the glass stopple of the phial containing the hi* 

 tjrosufphuret and gas, to prevent its being completely closed. 

 Without this precaution a vacuum is formed by the absorp- 

 tion of the oxigen gas, which occasions the evolution of the 

 nitrogen that impregnates the Hquid. 



I let the mixture of hidrosulphuret and* gas to be analys- 

 ed stand at rest for five days, in which time** the process i3 

 always finished. In this way J obtained more regular re- 

 sults, than those obtained in a few minutes by agitation ac- 

 cording to Marty.' s prpcess. % , ^ 



I take care, that the whole of the process is conducted at 

 a temperature nearly uniform ; for, if the hidrosulphuret be 

 exposed to a lower degree of heat than that, at which it was 

 impregnated with nitrogen gas before being, placed in con- "***' 



tact with the gas to be examined, it absorbs nitrogen from 

 the latter ; on the contrary, at a higher temperature it adds 



t olt - iV«l 



Jhe eudiometrical process with the hidrosulphuret is more 

 accurate than Volta's process, as will appear hereafter, to 

 determine the proportion of exigen gas when mixed with 

 nitrogen only: but when the mixture contains carburetted 

 or oxicarburetted hidrosren gas, it is best to employ Volta's . r 



eudiometer, or some other process in which a large quantity v^ 



of water is not essential ; for the liquid hidrosulphuret, or 

 even pure water, sensibly absorbs all oxicarburetted hidro- 

 gen gasses, and makes the proportion of oxigen gas appear 

 larger than it really is. This observation is true however 

 only when the proportion of carburetted hidrogen exceed 

 one per cent of the gas analysed *. 



* The absorption of oxicaibu retted hidrogen gasses by hidrosulphuret Absorption oj? 

 of lime lias been announced by Mr. C, L. Bertbollet in his excellent pa i«» an »«iabl« 



% m t • HIIS565 "" 



per on these gasses in the Memoirs of tbe Society of Arcueil, vol, II, 

 p. 79. I bavc observed, that the olefiant gas is absorbed in equal quan- 

 tities by pure water and a solution of hidroguretted sulphuret of potash j 

 hut that pure hidrogen gas is absorbed in larger quantity by pu;e wafe^: 

 than by the liquid hidrosulphuret. 



