512 MR. W. C. D. WHETHAM ON THE VELOCITIES OF THE IONS. 
We thus find for the specific ionic velocity of the barium ion, travelling through 
a decinormal solution of barium chloride in solid agar jelly at a temperature of 18°, 
Vp, = 0000393 centim. per sec. 
For an aqueous solution of corresponding strength, KoHLRAUSCH calculates, that, 
in order to give the observed values to the conductivity and the migration constant, 
the barium ion must have a specific velocity of 
Vp, = 0'000366 centim. per sec. 
New solutions were then set up, the amount of sodium sulphate being only just 
enough to give a visible precipitate. The voltage used was less—about 24 instead of 
40, but otherwise the experiments were similar. 
The following mean results were obtained :— 
v = 0°244 centim. in 10 mins. 
Galvanometer = 22'7. Therefore y = 1:08/243. Mean conductivity of solutions 
9°57 X 1072 at 16°°9, ‘Temperature of water-bath 16°°9. 
Therefore 
v, = 0°000376 centim. per sec., 
which gives for the velocity of the barium ion at 18° the value 
Vga = 0°000386 centim. per sec. 
Calciwm.—The determination of the velocity of the calcium ion was not quite so 
satisfactory. The solutions used were decinormal ones of calcium chloride and sodium 
chloride, sodium carbonate being added to the latter as indicator. The precipitate of 
calcium carbonate was only visible when a considerable amount of sodium carbonate 
was present. This would make the change in concentration, due to the precipitation, 
considerable, and tend to increase the potential gradient at the boundary, and make 
the observed velocity greater. 
The galvanometer had been moved, so that it was re-graduated. 

za | 
| || 
1] 

ee 
| Resistance. | Galyanometer. | — Resistance. Galvanometer. | 
| Bide pose a 
| ohms. | | | ohms. 
180 | 27°5 150 31:5 
| 170 29°3 | 140 33°5 
| 160 30:1 i 130 35'1 
| 

To these resistances 10 ohms must be added for the galvanometer and leads. 
