APPARATUS FOR SILENT DISCHARGE. 



225 



spirally on its external surface (Fig. 34), this strip being fixed 

 with gum. The whole glass surface in contact with the 

 atmosphere is carefully coated with shellac, in order to insulate 

 it more fully. 



(2) A V tube (Fig. 35), slightly less in diameter than the 

 test-tube, so arranged as to be able to be introduced into it, 

 almost without friction. 



This tube is closed at one of its ends (Fig. 35), and filled with 

 dilute sulphuric acid. 



The test-tube being placed over a large mercury trough, the 

 gases on which it is desired to operate are introduced into it 

 after having been measured in a graduated test-tube with the 

 usual precautions. The volume is regulated according to the 

 capacity of the test-tube, diminished by that of the vertical 

 portion of the V tube. It is also necessary to take account of 

 the increase of volume pro- 

 duced by decomposition, if 

 there be occasion to do so. 

 The closed part of the V tube 

 is then introduced into the 

 interior of the test-tube, first 

 having been filled with water 

 acidulated with sulphuric 

 acid. 



Then, the test-tube being 

 held in the left hand, a small 

 porcelain basin, like those 

 usually employed for measur- 

 ing nitrogen in organic com- 

 pounds, is introduced by the 

 right hand under the mercury, 

 and passed under the test- 

 tube, held vertically, when Fig - 35> 

 the whole is taken away, so as to isolate the test-tube arranged 

 over the basin, as in Fig. 36. 



It is held in place with the aid of the wooden jaw of a 

 Gay-Lussac support, which, for the sake of simplicity, has not 

 been shown. This support, at the same time, applied against 

 the platinum strip in Fig. 36, keeps in place a thin sheet of 

 platinum, fixed at the end of a wire communicating with one 

 of the poles of a very large Euhmkorff coil, whilst the other 

 pole is attached to a second wire which dips into the acidulated 

 water of the V tube. 



12. The combination of nitrogen with hydrogen, as well as 

 that of oxygen and nitrogen, ceases below a certain potential of 

 the electric apparatus, which produces the silent discharge. It 

 does not take place at all at the low tensions. 



13. The combination of free nitrogen with the hydrocarbon 



Q 



