DISCHARGE OF ELECTRICITY FROM HOT PLATINUM. 
271 
except at pressures of several millimetres. The following values of the positive leak 
were obtained at 1300° C., using 160 volts:— 
Pressure. 
Positive leak. 
millims.. 
amperes. 
766 
40 X 10-9 
156 
24 X 10-9 
9 
4 X 10-9 
The following table gives the values of the negative leak at a temperature of 
1400° C. in hydrogen at several pressures :— 
Pressure. 
Current per square 
centimetre. 
millims. 
amperes. 
13.3 
1 X 10-3 
0-112 
l-2x 10-5 
0-0013 
2 X 10-' 
0 
1-2 X 10-10 
The last number is the leak from a very well cleaned wire in air at a low pressure. 
The leak obtained l^y Mr. Richaedson at 1400° C. was al.iout 3 X 10~® ampere per 
square centimetre, with a gas pressure of about OT millim, 
(5.) The Leah from Palladium in Hydrogen. 
Some measurements were made of the leak from a palladium v/ire 0'2 millim. in 
diameter and 13 centims. long. The wire was left about 20 hours in hydrogen at a 
few millimetres pressure ; after mounting it and l^efore it was lieated the pressure 
was reduced to 0'0003 millim. The balancing 
resistance (14) of the wire was 320 ohms at 
18° C. On heating to 14 = 1100, the negative 
leak with 200 volts was 3 scale divisions 
(1 division = 3x10“® ampm’e) and the positive 
leak 750 divisions. After five minutes tlie leaks 
fell to 0’5 and 130 divisions respectively, while 
the pressure rose to 0'022 millim. The positive 
leak continued to fall with the time, and 
ultimately, after several hours’ heating, became 
only 6 divisions with 14 = 1550 ohms. It was 
found that the positive leak was quite inde¬ 
pendent of the pressure of the liydrogen, while the negative leak increased nearly 
proportionally to the pressure at small pressures. Fig. 8 shows the variation of the 
leaks (P.D. = 200 volts) with the pressure, the resistance R being 1400 ohms. 
