1(5$ fOMBTTSTION OF «HARCOAL AND OF HlDROGEtf. 



Separation of To separate the carbonic acid gas from the oxigen and ni* 

 acid l trogen after the combustion of the charcoal, I employed 



the mercurial pneumatic apparatus. I immersed the mer- 

 cury in the small globe, which by means of the vacuum ex- 

 tracted the gas from the receiver, where the combustion had 

 been effected ; and I passed the air contained in this globe 

 into a wide tube rilled with mercury, which was long enough 

 to allow the column of gas to stand about 0*^7 of a met. 

 [10-6 inch.] high. I then introduced through the mercury 

 one or two grammes [15 or 30 grs.] of highly concentrated 

 solution of potash, agitated the solution in the gas occasi- 

 onally, and in a few hours the whole of the acid gas was 

 condensed. I then replaced the mercury by water and mea- 

 sured the absorption. 

 Separation of Experience has shown *^e, that, when the carbonic acid 

 carb nir acid j mixed with oxitft-r: gas nearly pure, considerable mis- 



by lime water takes are made in separating the two gasses by lime water. 

 °£ l ^° d be de " This liquid, by means of the agitation required for the com- 

 plete Condensation of the acid gas, absorbs oxigen gas. This 

 effect is not produced by the lime, but by the water of the 

 solution, which is required to be in very large proportion to 

 Potash prefer- the volume of gas*. Liquid potash absorbs nearly the 

 same proportion of oxigen gas as an equal bulk of lime wa- 

 ter ; but as the solution of potash maybe used in an infi- 

 nitely less quantity, the errour arising from it is too small 

 to be noticed, 

 I/ime water Lime water affects the result too, not merely by absorb- 



Soeen° Ut m ' * n £ ox *£ en S as » but by replacing it by nitrogen gas, with 



which it is always more or less impregnated f. 

 but may be When the acid gas is mingled with common air, or with 



t»s«d when ox jg en ga 5 contaminated by a large proportion of nitrogen, 

 h prtsent. lime water may be employed to absorb the acid gas without 



any sensible errour. 

 Experiments The following is the mean result of my experiments on 

 on the abiorp. this su bj e ct, under a temperature of 14° [57'2° F.]. The 



* This affects the calculation from the quantity of gas absorbed, not 

 that from the precipitate thrown down. C. 



f This would alter the state of the residual gas, it is true; but it 

 wculd tend to correct the calculation made from the quantity of gas ab- 

 sorbed. C. 



lime- 



