improved Sliding-Rod and of the Volumescope. 1 ] 7 



Description of the Contrivance for the removal of Carbonic Acid 

 from the Gas left after exploding Gaseous Mixtures, partly 



consisting of the Compoimds of Carbon. 



TI)e glass receptacle R fastens by means of a gallows screw 

 to a knob at the end of a perforated cylindrical projection from 

 the cock L, so as, with the aid of intei'posed leather, to make 

 an air-tight juncture. Between the gallows screw and the re- 

 ceptacle, another cock S is interposed, the bore of which com- 

 municates by means of corresponding perforations with that 

 of the cock L. 



Below the receptacle a caoutchouc bag is fastened, which, as 

 well as the receptacle, must be filled with lime-water. 



Means of causing the Explosion of Gaseous Mixtures tsoithin the 

 Receiver of the Sliding-Rod Eudiometer. 



A gaseous mixture, when contained in the sliding-rod eu- 

 diometer, may be inflamed by galvanic ignition excited in a 

 platina wire, in a mode analogous to that already described 

 in the case of the barometer-gauge eudiometer. See Phil. Mag. 

 and Annals, vol. iv. p. 130. 



The circuit is established by means of the leaden rods x x, 

 one of which communicates with the mercury of the cistern, 

 while the other is fastened to the insulated wire by means of the 

 gallows z. To the rod which communicates with the mercury, 

 a piece of iron should be soldered so that the lead need not be 

 immersed, and consequently corroded. The insulated wire, 

 where it enters the cavity of the eudiometer, is made air-tight 

 by means of a small stuffing-box. It is protected from the 

 mercury within the receiver by a covering of twine, well soaked 

 in and coated with shell lac varnish. 



Determination of the Qjiantity of Carbonic Oxide in a Gaseous 

 Mixture, by the impoved Merairial Sliding-Rod Eiidioineter. 



In the first place the mixture must be well washed witli 

 lime-water, or a caustic alkaline solution, in order to remove 

 carbonic acid, if present. In the next place let us imagine the 

 bell-glass O N, after being adequately supplied over the pneu- 

 matic cistern with ecjual measures of the purified mixture and 

 oxygen gas, has been transferred to the jar I, containing a 

 sufliciency of water to displace the gaseous mixture as re- 

 quired. 



In order to fill the receiver with gas, through the gauge-tube 

 and the pipe Q, by which it conmiunicates with the gaseous mix- 

 lurc in the bell-glass, thccudiometer must be filled with mercury 

 to the total exclusion ofair, and the sliding-rod wholly within 

 its tube. Under these circumstances the spring being pressed 



upon 



