DISCHARGE OF ELECTRICITY FROM HOT PLATINUM. 
251) 
to 0, hence we may write = h''N\/d, where U is a constant, 
above equation we get 
, _ Q„ j I n 
U* ' = Ei() ' 
Substituting this in the 
In the case of hot platinum in an atmosphere of its own ions, if a' is tlie current per 
unit area due to ions leaving tlie ]datinnm surface, then a; = Nc, where e is the charge 
carried by one ion. Hence we get, putting R ■— 2, which is its value in small calories 
for one gramme molecidar weight of any gas, 
loo- — y<) I j _ '1 
The following taljle gives the values of Q calculated l)y means of this equation from 
the observed currents and taking a = 0. Tlie numbers in brackets indicate which 
pair of experimental numbers taken from the last table given aljove was used. 
Mean temperature. 
Q. 
° 0. 
(b 2) 
1392 
138,500 
(2, 3) 
1425 
132,000 
(3, 4) 
1459 
124,400 
(J, 5) 
1493 
133,500 
(5, 6) 
1528 
126,300 
(6, 7) 
1563 
132,000 
Mean . .* . 
131,100 
The variations in Q are not greater than can l)e ascribed to experimental errors. 
The value of Q obtained corresponds to a fall of tlie ionic charge through 5'74 volts. 
Riohardson’s residt for this quantity was 4H volts, but since the leaks which he 
obtained are about lOOU times greater than those given above, it was to lie expected 
that his value of would l:)e smaller than that which my experiments lead to. 
The value of the constant A in the formula x = calculated from the value 
of the current per square centimetre at 1580° C., is 6’9 X IC^, so that the equation 
becomes 
X = G-9 X 
The following table contains a comparison of the currents calculated by ineaus of 
this formula and those found experimentally :— 
•) r -y 
w 1 j w 
