Ionization produced hy Heated Salts. 



379 



potential reading. Schmidt* investigated in detail the 

 effects produced by a reversal of the electric field, using 

 cadmium iodide at temperatures of 260° 0. and 332° 0. and 

 sl pressure of 3*7 mm. The results recorded in Table II. 

 agree in general with those of Schmidt in the case of the 

 effects observed in tube B. The results, however, in the 

 salted tube A (which should be compared with Schmidt's 

 results) are quite different. 



The ionization produced by cadmium iodide under positive 

 and negative potentials was further investigated by making 

 use of a modification of the apparatus shown in fig. 1. 

 The glass portions were similar in form to those previously 

 described ; the tubes were 15 cm. in length and 1 cm. in 

 diameter. The arrangement of electrodes in tube B was the 

 same as shown in figure 1. The inner electrode, however, 

 of the tube carrying the salt consisted of a closed platinum 

 ■cylinder fitted in symmetrically with respect to the outer 

 platinum gauze. The distance between these two electrodes 

 was 2 mm. It was thus possible to obtain saturation with 

 greater surety, allowing the passage of uncharged matter 

 only into B. The experiments with this apparatus were 

 made at a temperature of 353-360° C. and at a pressure of 

 1 cm. Saturation was obtained in A for both positive and 

 negative potential currents with 80-120 volts. Table III. 

 •contains data for representative current-E.M.F. curves. 



Table III. 



Tube A. 



Tube B. 



V 



+ 



_ 



+ 



10 



3-6 



3-4 



• . • 



20 



50 



4-8 





40 



6-3 



56 



KV0 20 



80 



9-8 



5-8 



26-3 3-4 



120 



10-2 



6-2 



29-0 51 



160 



10-8 



7-0 



301 5-3 



200 



137 



8-3 



320 70 



The current-time effects were examined in both tubes 

 under the saturating potential of ±120 volts. The pressure 

 was 1 cm. and the temperature 358-363° C. The ionization 

 in the salted tube, under either a positive or negative 

 potential, fell off from an initial maximum and reached the 

 steady state after forty minutes' heating. This constancy 



* Loc. at. 



