BETWEEN MURIATIC ACID AND CHLORINE. 341 



refuses to issue from a good electrophorus, or even little ma- 

 chine. Besides, no discharging rod or communicating-wire is 

 here required. Holding the eudiometer in the left hand, we 

 turn the handle of the machine, or lift the electrophorus plate 

 with the right, and approaching the little ball, the explosion 

 ensues. The electrician is well aware, that a spark so small as 

 to excits no unpleasant feeling in the finger, is capable, when 

 drawn off by a smooth ball, of inflaming combustible gas. 

 Even this trifling circumstance may be obviated, by hanging 

 on a slender wire, instead of applying the finger. 



We may analyse the residual gaseous matter, by introducing 

 either a liquid or a solid re-agent. We first fill the open leg 

 nearly to the brim with quicksilver, and then place over it the 

 substance whose action on the gas we wish to try. If liquid, 

 it may be passed round into the sealed leg among the gas ; but 

 if solid, fused potash for example, the gas must be brought 

 round into the open leg, its orifice having been previously clo- 

 sed with a cork or stopper. After a proper interval, the gas 

 being transferred back into the graduated tube, the change of 

 its volume may be accurately determined. With this eudio- 

 meter, and a small mercurial pneumatic cistern, we may per- 

 form pneumatic analyses on a very considerable scale. 



It may be desirable in some cases, to have ready access to the 

 graduated leg, in order to dry it speedily. This advantage is 

 obtained, by closing the end of the syphon, not hermetically, 

 but with a little brass cap screwed on, traversed vertically by a 

 platina wire insulated in a bit of thermometer tube. After 

 the apparatus has been charged with gas for explosion, we con- 

 nect the spherical button with the top of the wire. 



With the above instrument I have exploded half a cubic 

 inch of hydrogen mixed with a quarter of a cubic inch of oxy- 

 gen ; 



