Vapour from electrified Still Surfaces of Liquids. 223 
changes were made in the arrangement of the apparatus. In 
place of the condensing-disk there was used a platinum disk 
of 12 centim. diameter, which could be connected at will by 
means of platinum wires, either directly with the needle of the 
electrometer or with the condenser-plate B. The porcelain 
dish in the sand-bath was replaced by an iron dish containing 
the mercury to be evaporated. Platinum or iron was neces- 
sary, because all metals which amalgamate with mercury 
show peculiar electric action, the causes of which I have not 
yet succeeded in detecting. At 200° 0. the mercury vapour 
was visibly condensed upon the platinum disk C, and very 
copiously from 200° to 360° C. It is necessary in the expe- 
riments that the surface of the mercury be kept perfectly free 
from oxide. 
First, the experiments were conducted according to the 
method on page 220 ; i. e. the platinum disk C was in direct 
connexion with the electrometer-needle, and after the mercury 
was swung under C was insulated with the needle. During 
the two minutes while the mercury was under 0, and elec- 
trified by 480 zinc-water-copper elements, the electrometer- 
needle showed the following deflections: — 
70 scale-divisions = 1 Daniell. 
Positive charge of 404 Daniells. 
Experiment. 
Mercury at 
room-temp. 
Mercury at 
360° O. 
1 
+ 8 
+10 
+ 6 
+ 4 
+14 
+15 
+ 5 
+ 5 
2 
3 
4. 
Secondly, the mercury was charged by a Topler electrical 
machine to a high potential, and observations were made 
according to the method described on page 218; i.e. the disk C 
was connected with the condenser-plate B of the Kohlrausch 
condenser, and with this was insulated before the mercury was 
swung under C. The plate A was ^ millim. distant from B, 
and during the two minutes of the experiment was connected 
with the earth. After the mercury was swung away from C, 
A was first insulated and then separated from B. By this 
method the insulating-power of B and C evidently comes into 
consideration. The results of this method are as follows : — 
