268 Chemical Instruments and Operations. 



Description of the Water Gage. 



The gage consists of three tubes, the interstices between 

 which are partially supplied with water. In the first place a 

 larger and outer glass tube, O M, open at the upper end, is 

 at the lower end cemented into a socket attached to the 

 cock, O, of the bell glass. Secondly, a small tube of varnish- 

 ed copper, the axis of which is made to coincide with that of 

 the larger tube, is inserted into the bore of the cock. Lastly, 

 a glass tube in size and situation intermediate between the 

 tubes just mentioned, and open at the lower end, at the up- 

 per end enters the pipe, Q,, which communicates with the 

 bore of the cock, K, and of course when this is open, with 

 the cavity of the receiver. When water is poured into the 

 tube, M, if the pressure within and without be in equilibrio, 

 it rises in the interstices between the three tubes to the same 

 height ; but whenever there is any diversity of pressure be- 

 tween the air of the inner and outer glass tubes, it is indica- 

 ted by a consequent difference in the height of the liquid col- 

 umns included. 



Description of the Contrivance for the removal of Carbonic 

 Acid^from the Gas left after exploding Gaseous Mixtures, 

 partly consisting of the Compounds of Carbon. 



The glass receptacle, R, fastens, by means of a gallows 

 screw, to a knob at the end of a perforated cylindrical pro- 

 jection from the cock, L ; so as, with the aid of interposed 

 leather, to make an air- tight juncture. Between the gallows 

 screw and the receptacle, another cock, S, is interposed, the 

 bore of which communicates by means of corresponding per- 

 forations 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, with- 

 in 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 gage eudiometer.* 



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

 one of which communicates with the mercury of the cistern, 



* See Art. 128, p. 127, of the Compendium, 



