Ionization produced by Heated Salts. 



381 



superimposed upon a rapid growth of current with time 

 appeared soon after the heating had been commenced. Obser- 

 vation showed that the vaporized salt condensed on the cooler 

 glass portions of the electrodes and finally bridged across, 

 forming an increasingly better conductor as time went on. 



Ionization Effects loith Iodine and a Comparison with iliose 

 given by Cadmium Iodide, 



Shortly after the experiments just described (Table IV.) 

 had been commenced, a heavy cloud of what seemed to be 

 iodine vapour appeared in the unsalted tube B. There was 

 little indication of its presence in other portions of the 

 apparatus. This vapour condensed upon the cooler parts of 

 the tube and electrodes and partially disappeared with time. 

 The tube had a strong odour of iodine when opened. Similar 

 phenomena were observed in other experiments. 



These observations suggested that the liberation and 

 ionization of the iodine constituent might play an important 

 role in the current-time relations, especially in the effects 

 observed in the unsalted tube. A considerable quantity of 

 iodine was, therefore, inserted in A, and the conditions of 

 the previous experiment, using cadmium iodide, as to tem- 

 perature, pressure, and potential were duplicated. The 

 current-time relations in the tube containing the iodine are 



Fi<?. 4. 



30 40 50 o 10 

 Time — Minutes. 



given in fig. 4, (o) indicating positive readings and (•) 

 negative values. Curves 3 and 4 of this figure show the 

 corresponding relations in tube B. These curves show that 

 Phil. Mag. S. 6. Vol. 25. No. 147. March 1913. 2 D 



