DISCHARGE OF ELECTRICITY FRO^I HOT PLATINUM. 
251 
Temperature on 
platinum scale. 
Correction. 
Temperature. 
o 
1066 
0 
° C. 
1066 
1100 
6 
1106 
1200 
26 
1226 
1300 
50 
1350 
1400 
83 
1483 
1500 
120 
1620 
1600 
164 
1764 
1638 
182 
1820 
The temperatures so determined in tliis way are sidyect to an error due to the ends 
of the wire being cooled by the thicker electrodes to wliich they are welded. There 
is also an error due to the resistance of these electrodes being measured along witli 
the wire and changing with the temperature. These errors are, however, almost 
entirely eliminated by the method of standardising the wire adopted, for the wire 
was standardised under nearly the same conditions as it was used under in the 
experiments, consequently these errors are reduced to almost zero at 1066° and at 
1820°, and are therefore very small at the intermediate temperatures. The numbers 
obtained consequently represent very nearly the tenq)erature of the wire at some 
distance from the electrodes. There was no appreciable error due to thermo-electric 
effects. 
It was found that after a wire had lieen just fused, as described above, the whole 
length of tlie wire, except about 1 centim. at each end, showed signs of fusion, 
although as soon as any part of the wire fused completely it broke, and so stojjped 
the current. The wires used were always about 13 centims. long, but in calculating 
the leak per sq. centim. of platinum surface, their length was taken as 1 centim. less 
than their actual length to allow for the cooling of the ends near the electrodes. 
This amounts to counting the 1 centim. of wire at each end as leaking half as much 
per unit area as the rest of the wire. 
The tube containing the platinum wire was sealed on to a tube which communi¬ 
cated with a Topler pump and McLeod gauge. The connecting tubes between the 
different parts of the apparatus were made short to enable the gas to get into 
equilibrium as quickly as possible. 
The methods used for preparing and purifying the different gases used will be 
described in the following sections. 
(2.) The Leah from Hot Platinum in Air, Nitrogen, and Water Vapour. 
The results obtained with air will first be described. The air was passed slowly 
through tubes containing soda-lime and calcium chloride and then let into the 
apparatus through a good mercury-sealed tap. A bulb containing phosphorus 
2 K 2 
