136 
MR. B. D. STEELE ON THE MEASUREMENT OF IONIC VELOCITIES 
Now, taking as an example solutions of calcium chloride, if we assume that v is not 
diminished in velocity, u only being affected, and assign such a value to x that the 
absolute velocity of the chlorine ions at the various concentrations = 0'000690 centim. 
second, tlie value given Ijy Kohleausch for the specific velocity, then we find 
that for 
N = O'o, X = 0'756 ; N = I'O, a; = 0'697 ; and N = 2'0, x = 0'610. 
For fhe corresponding solufions of sodium chloride, the figures are 
0'737, 0'678, and 0'590, 
or, solufions of calcium chloride are more dissociated than solutions of sodium chloride 
of the same concentration. If we assume, instead of this, that the ratio gives the 
correct values for x, and calculate the specific ionic velocities for the anion and the 
cation at different concentrations, we ol)tain the following figures ^or solutions of 
calcium chloride :— 
N = 0-5 . . . a = 0-000401 r = 0'000830 
I'O . . . 386 845 
2-0 ... 372 ' 867 
V for Cl from KCl or Na Cl at all concentrations = 0'000690. 
Thus we find fhat, uidess calcium chloride is much more dissociated than sodium 
chloride, the velocity of the anion steadily increases, and tliat of the cation steadily 
decreases with rise in concentration; and the same is shown by all the chlorides 
referred to in this paper whose transport numher increases with increasing N. 
The assumpti(»n of a variation in specific ionic velocity does not in itself seem to be 
sufficient to afford a proljalde explanation of the difficidties in cpiestion. 
The second explanation that we shall consider is one that was advanced in 1859 by 
Hittoef, who says (‘ Fogg. Ann.,’ 106, p. 385, 1859) : “■ Die Yerhaltnisse, welche von 
der Zunahme des Wassers abhiingen, und bei den Verbindungen der Metalle aus der 
jMagnesia-grujJiJe auf die Ueherfiihrungen so wesentlich einwirken, mlissen hei den 
Kaliuin und Ammoniumsalzen S(.) gut wie fehlen. Dadurch werden wir auf chemische 
Veranderungen der Constitution unserer Electrolyte, die mit der wachsenden Menge des 
Wassers eintreten, hingewiesen.” hi the case of the chlorides of zinc and cadmium, 
and of cadmium iodide, the change in p is so great tliat the ratio ^>1, as 
measured by Hittoef, or there is more current carried liy the anion than the total 
current—a conclusion which is obviously absurd. To exjilain these cases, he supposes 
that ionization takes place not only into the simple ions Cd and I, hut also, at least 
