412 
mund and Drucker ‘) suggested the value 338 at 25 * 2 * 4 * 6 ; and then 
Drucker 2 ) used the valne 312 at 18° and 345 at 25°. Again, 
Drucker 8 ), Goodwin and H askei, l 4 ), and Whetham 6 ), by combining 
their molecular condnctivity measureraents with the transference 
ratios obtained by Jahn and his pupils, and Tower deduced the 
mean value for hydrion equal to 313 at 18° or 346 at 25°. Kohl- 
rausch 6 ) again, and Jahn and his pupils 7 ), ’deelared the most 
probable value of hydrion to be 315 at 18° or 348 at 25°. Gorke 8 ) 
obtained the value 353 at 25° from measurements of picric acid. 
Noyes and Kato 9 ) came to the value 315 at 18° or 348 at 25° 
from migration ratios of nitric and hydrochloric acids. Drucker and 
Kisnjair 10 ) again gave the value 313 at 18° or 346 at 25°. It 
would be quite evident from these that the value for hydrion is 
far from being correctly known. 
Now, by applying Kohlrausch’s formula for the temperature 
coëfficiënt of mobility we can get the values of ions at 0° from' the 
val ues given at 18 or 25°. But this empirical formula holds good 
with rigidity in the neighbourhood of 18°; so results deduced at 
0° are rather uncertain. Moreover Kohlrausch himself has changed 
these values of temperature coefficients many times. For comparison, 
are added below the tables (see p. 41 6) of temperature coefficients («) 
as published by Kohlrausch 11 ) in 1901, and 1908. 
Thus extrapolation to 0° is rather uncertain. With a view to deter- 
mine exactly the ionie velocities at 0°, this investigation was under- 
taken. Noyes and Falk 12 ) have given very accurate tables collected 
from the work of numerous in vestigators for the transference numbers 
of varioüs substances at almost infinite dilution and at 0°. From the 
molecular conductivity determination at 0°, the sum of the ionic 
o u 
velocities at 0 is obtained (since oo — u -f- v), and - is taken 
v 
from Noyes and Falk’s tables ; thus u and v are obtained. 
9 Zeit. Phys. Ghem. 1903, 46, 827. 
2 ) Zeit. Phys. Ghem. 1904, 49 , 563. 
8 ) Zeit. Elektrochem. 1907, 13, 81. 
4 ) Proc. Amer. Acad. 1904, 40, 399. 
B ) Zeit. Phys. Ghem. 1906, 55, 200. 
6 ) Zeit. Elektrochem. 1907, 13, 333. 
7) Zeit. Phys. Ghem. 1907, 58, 641. 
8 ) Zeit. Phys. Ghem. 1908, 61, 495. 
») Zeit. Phys. Cliem. 1908, 62, 420. 
10) Zeit. Phys. Ghem. 1908, 62, 731. 
u ) Sitzungsber. d. Berl. Akad. 1901, 1026; 1902, 572; Proc. Roy. Soc. 71, 338 
(1903). Zeit. Elektrochem. 14 (1908), 129. 
12 ) loc. cit. 
