563 



the electrodes are fastened. By means of an intermediate piece the 

 two legs are connected with each other aiid with the water-jet 

 siiction-pnmp, which immediately removes the oxjhjdrogen gas 

 formed in the electrolysis. The Inminesceiice is started by tiie im- 

 mersion of the cathode, and at the same time the cell is closed 

 air-tight. In the metal chromoscope the lube drawn in fig. 2 comes 

 in the place of the f/'-tube. 



In order to photograph the spectra, the light was thrown on the 

 slit of a Hii.GER spectiogra[)h by means of a small condenser with 

 small focal distance. When Viridin-Inalo plates were used, the expo- 

 sure had sometimes to be continued from 40 to 150 minnles, be- 

 cause spraying took place. As electrolyte HNO, 1 : 4 was generally 

 used ; other electiolytes, however, may equally well be used, e.g. 



Fig. 1 



Fig. 2 



diluted or concentrated HjSO^, KOH etc.; this brings about no 

 essential difference as to the nature of the phenomena. 



-37* 



