102 Discharge of Positive Electrification hy Hot Metals. 



The temperatures are given in degrees centigrade, the rates 

 of leak in scale-divisions per hour. 



By interpolation it was found that the rate of 10 div. per 

 hour was attained at 270°. The same wire was again taken 

 up the scale of temperature without removing it from the 

 apparatus. 



Temperature.. 13° 194° 210° 217° 227° 240° 258° 

 Leak -5 '7 134 T96 5-5 67 45-6 



The rate was 10 div. per hour at 250°, 20 degrees lower 

 than before. 



This change in the temperature at which an assigned rate 

 of leak (10 per hour) was attained is, of course, far beyond 

 the uncertainties of experiment, and must be attributed to a 

 change in the state of the silver surface. Further heating 

 did not alter it much more. 



The apparatus was exhausted, filled with pure hydrogen, 

 and the pressure reduced to 1 cm. 



Temperature. . 15° 

 Leak -2 



10 div. per hour at 228°. 



Thus the leakage set in in hydrogen at a somewhat lower 

 temperature than in air. 



The next experiments were made with a copper wire sub- 

 stituted for a silver one. This wire was cleaned with emery 

 paper before it was put in ; in the course of the experiment 

 it became oxidized. This oxidizing process did not appa- 

 rently facilitate the escape of positive electrification since the 

 leakage was not so soon apparent as in the case of the silver 

 wire. 



The results were : — 



Temperature.. 167° 226° 2o3 e 271° 289 c 308° 325° 331° 

 Rate of Leak . -1 -3 -55 2'9 120 380 204-0 340-0 



Thus the rate of leak was 10 div. per hour at about 287°. 



A repetition of the experiment gave a very similar result. 



The copper wire was taken out and thoroughly oxidized 

 in a blowpipe flame. It was then replaced. The rates of 

 leak were as follows : — 



17.5° 



183° 



210° 



225° 



233° 



•6 



1-0 



2-5 



6-] 



14-8 



Temperature . . 



. . 255° 



259° 



272° 



283 



Rate of Leak . . . 



•7 



311 



150 



83-2 



Here the rate of leak was 10 div. per hour at 266°. 



