496 



SEC. 13. CHEMISTRY. 



At a superior level is placed a glass jar r, containing pure and concen- 

 trated sulphuric acid ; this jar is connected by a syphon tube s (in which is 

 placed a glass stop cock) with the lower cylinder q. This upper jar, which 

 I shall term the reservoir, is closed by a cap t, through which the siphon 

 tube passes, and in which is also fitted a second glass tube u. The gas from 

 the induction tube is delivered at w, whence it passes into the gas-holder by 

 an arrangement of tubes, which is best understood from the drawing. The 

 passage of the gas is regulated by means of an air pump, connected with the 

 glass tube u by a tube of caoutchouc. 



The volume of gas submitted to experiment was measured in a glass 

 pipette, of which a drawing is given in Fig. 3. The capacity of the pipette 

 (290 8 sub-centimes) between the two marks b and c was estimated by cali- 

 bration with mercury. It was then welded to a glass tube of the form given 

 in the figure ; is a reservoir of sulphuric acid with a syphon tube attached ; 

 d a, cylinder containing water, in which the pipette a is immersed, and in 

 which a thermometer is placed. The gas pipette is connected with the gas 

 holder by a paraffin joint at /. The arrangements for working this pipette 

 are similar to those in the case of the gas-holder. 



In order to estimate the changes in bulk which the electrized gas under- 



Ftc.S. 



