270 Chemical Instruments and Operations. 



bell, its density, within the receiver, will be unduly great. 

 Hence, the pressure of the screw on the spring must be re- 

 laxed until the gage indicate that the gas within the receiver 

 has, by the escape of a portion of it, become with respect to 

 pressure in equilibrio with the atmosphere. The cock com- 

 municating with the gage, is then to be closed, the pressure 

 on the spring restored, and an explosion effected. The com- 

 munication with the gage is now to be opened. The indi- 

 cated deficit must be compensated, and measured, by push- 

 ing in the rod, until the columns of water in the interstices of 

 the gage are on a level. In the next place, close the cock, 

 K, communicating with the gage, and open the cocks, H L S, 

 which are between the receiver and the receptacle, R. Into 

 this receptacle, by forcing the rod home, the gas is to be 

 transferred. Being agitated by the lime water, it is drawn 

 back into the eudiometer, brought into equilibrio with the 

 atmosphere, by appealing again to the gage, and then meas- 

 ured by noticing the number of graduations which the sliding 

 rod must enter, in order to effect its expulsion. This residu- 

 al air, and the deficit produced by the explosion being de- 

 ducted from two hundred, the remainder will be the quantity 

 of the carbonic acid, and of course of carbonic oxide origi- 

 nally in the mixture ; since carbonic oxide, in passing to the 

 state of carbonic acid, absorbs half of its bulk of oxygen 

 without any enlargement of volume. 



3. ANALYSIS OF OLEFIANT CAS. 



As a volume of this gas has been ascertained to be equiv- 

 alent to two volumes of carbon, and two volumes of hydro- 

 gen, it must require three volumes of pure oxygen for its 

 complete combustion, and must leave, after the union, two 

 volumes of carbonic acid. In order to insure a competent 

 supply of oxygen, four volumes of it may be mixed with one 

 of the olefiant gas in the bell glass, and the same manipula- 

 tion resorted to, as in the case of carbonic oxide, excepting 

 that before the explosion, the rod, V, must be drawn out to 

 the greatest extent ; and that as soon as the explosion has 

 taken place, the rod must be returned into the tube, so as 

 nearly to compensate the condensation, before resorting to 

 the gage. 



