1905-6.] Electrolysis through Precipitation Films. 
457 
A very satisfactory film was formed, and the conductivity was 
determined at various temperatures. The temperature coefficient 
was calculated from the formula 
JL K,-K g 
K 9 , t- 25 
in which and K 25 are the conductivities at temperatures t and 
25° C. 
The results are as 
follows : — 
Time. 
Temperature. 
Conductivity in mhos. 
c. 
12.0 p.m. 
25*0° C. 
•001523 
... 
12.30 „ 
12-0 „ 
835 
•0348 
1.0 „ 
12-3 „ 
869 
338 
2.0 „ 
0-3 „ 
544 
260 
3.30 „ 
16-2 „ 
1105 
312 
4.30 „ 
25*0 „ 
1782 
. . . 
Following morning 
25*0 „ 
1517 
B. Effect of a chromic hydroxide film made in sulphate solutions 
on the other salts. 
In this series of experiments solutions of ammonium chloride, 
ammonium bromide, and of ammonium sulphate were prepared so 
as to have the same specific conductivity ; the concentrations 
were *25 mol. NH 4 C1, ‘25 mol. NH 4 Br, and about T7 mol. 
(jST[ 4 ) 2 S0 4 . A film of chromic hydroxide was then formed 
in the unsymmetrical cell exactly as described in the previous 
experiment. 
When the final conductivity had been constant for several days, 
the mixed solutions were replaced by the T7 mol. (NH 4 ) 2 S0 4 
solution, w r hich was allowed to remain until the readings were 
constant. This solution was then replaced by a fresh portion of 
the ammonium sulphate solution, but the readings were found to 
be the same as before. The ammonium sulphate solution was 
similarly replaced by the ammonium chloride solution, and the 
chloride by the ammonium bromide solution ; and, in conclusion, 
the bromide solution was washed out with the ammonium sulphate 
