388 Prof. CI Shear d on the 



No effects were observed in contradiction to the facts already 

 set forth. Nor can the large negative emission from the 

 original salt be attributed to moisture. A thick paste of fresh 

 salt of about 3 grams weight was made and the ionization 

 effects determined at a pressure of 1*8 cm. and a temperature 

 of 480-90° C. The negative current fell off asymptotically 

 with the time from a maximum of 200 x 10" 10 ampere, a value 

 about one-eighth of that shown in curve 2, fig. 6. The 

 positive ionization, however, from the moistened salt was 

 increased tenfold. When the distillate was removed from the 

 inner electrode it was found coated on the inside with a thin 

 blackish coloured film, a phenomenon which was not observed 

 in other experiments. 



Chemical Analyses of the Distillates. 



Chemical analyses were made as to the percentage of iodine 

 in (1) a sample of the cadmium iodide (Einer and Amend) 

 used, (2) of the fifth distillate obtained at 1 cm., and (3) of 

 the tenth distillate at 2 cm. pressure. The following- 

 percentages of iodine were found : (1) 72*14, (2) 70*27, and 

 (3) 65*85. Hence continued distillation diminishes the per- 

 centage of iodine. This fact lends farther support to the 

 view that the negative ionization consists in large part of 

 the iodine constituent. 



Conclusions. 



The following points have been fairly definitely estab- 

 lished : — 



(1) There can be an ionization in the secondary chamber 

 B when only uncharged matter enters B, since there is a 

 saturating potential in A. Thus the ionization is partially an 

 ionization of the vapour. This may arise from the action of 

 the vapour on the electrodes or it may be a volume ionization, 

 or both. 



(2) In addition there is an emission of ions from the salt, 

 as shown by the experiments with the air-cooled electrode 

 apparatus. Furthermore, the presence of negative ions is 

 definitely proven. There is a large initial negative emission 

 and practically no positive on heating a sample of the original 

 salt. As the heating continues the positive ionization in- 

 creases to a maximum and then falls away; the negative 

 continually diminishes. 



(3) The ionization in the unsaltod tube B may equal or 



