( 279 ) 
mum, after which it will fall until a constant value is reached, 
whieh would indicate the attainment of equilibrium. 
It was to be expected that the attainment of the final condition 
would be slow, considering that the contents of the cell were not 
stirred and that the saturation of the liquid with HgO was brought 
about by diffusion. 
The correctness of these views was proved numerically by all 
the experiments. In the following table the time in hours, from the 
first filling of the cell, is given under ¢, the E.M. F. of the element 
(at 25°,0) at the time mentioned is given under Z in millivolts. 
TABLE II. 
t. (hours) E. (Millivolts) t (hours) JE (Millivolts) 
0 0,585 61 1.037 
3/4 0,759 73 0,876 
11/, 0,843 97 0,756 
51, 1,066 121 0,721 
24 1,237 147 0,703 
- 293/, 1,237 LEE 0,686 
49 1,169 194 0,685 
241 0,685 
Representing the E.M, F. graphically as a function of the time, 
the curve in fig. 2 is obtained. A maximum is attained in 24 hours, 
t Be nt 
EP nc SRB ll teu BREE ER 
da A EEE WEBA àl 
Eet ADE ed | BRE Bese 
<i, ees ate le eal el ble 
REE Ie 
TAAI ere Pel TT 
ry (0540829 400 B U WM MI IM 14 2d 
Time in hours > 
Fig. 2. 
the condition of equilibrium being reached only after tbe lapse of 
171 hours; this was observed for a further 70 hours. 
According to this experiment the difference of potential between 
red and yellow mercuric oxides at 25°,0 is equal to 0,685 millivolts. 
2. Although, as above mentioned, impurities could not be discov- 
ered by analytical methods in the specimens of red and yellow 
mercuric oxide used yet, considering the great delicacy of the electric 
20* 
