510 MR. W. C. D. WHETHAM ON THE VELOCITIES OF THE IONS. 
nearly equal specific 1esistance, so that the uncertainty, which must appear in the 
result, shall be, at all events, as small as possible. 
Bariuwm.—Decinormal* solutions of sodium chloride and barium chloride, the former 
containing a little sodium sulphate, were made up with agar jelly just strong enough 
to set. The resistance of each was determined in a cell of the form shown in fig. 2, 
Fig. 2. 


the constant of which was known, and gave the conductivity of any solution in 
reciprocals of legal ohms, by dividing 1°5596 by the observed resistance measured in 
legal ohms. 
Resistance of sodium chloride solution at 15°°8 =: 161°8 ohms. 
is barium a 45 a 163°0__,, 
* = Ei , 13°4= 1730 ,, 
I 
The temperature coefticient of resistance is, therefore, about 2°5 per cent. per degree, 
and the mean conductivity of the two solutions at 15°°8, 9°60 X 107%. 
A small tangent galvanometer was adjusted and graduated by passing the current 
from a freshly prepared Daniell’s cell through it and a box of resistance coils arranged 
in series. The following readings were obtained— 






Resistance. Reading. | Resistance. Reading. 
vbms. a , onms. @ 
250 216 170 28:7 
240 22°1 | 160 29°8 
230 22°9 | 150 313 
220 23:8 140 32:7 
210 24-5 130 34:5 
200 25-4 120 361 
| 190 2674: 110 384 
| 180 27°5 100 40:6 


The resistance of the galvanometer and its leads was 10 ohms. 
* A decinormal solution contains one-tenth of the equivalent weight of the substance in grams in one 
litre of solution, e.g., 1 x $ BaCi, =°1 x 4 (137 + 70°8) = 10°39 grams per litre. 
