THE ELECTRICAL RESISTANCE OF THIN LIQUID FILMS. 
487 
solution from which it is formed, may in the course of 40 minutes lose 233 out of the 
57‘7 volumes of water originally contained in every 100 volumes of the solution. 
A. V . 
(2.) The values of —— increase as the film gets thinner, but in all cases are much 
smaller than the value of the same quantity calculated from the moment at which the 
film was formed to that at which it reached a thickness of 14 X 10~ 5 centims. Hence, 
as we should expect, the greater part of the loss, whether measured by the total 
amount of water evaporated or by the change in the constitution of the film, takes 
place in the first few minutes. As the film thins, however, the evaporating surface of 
a given quantity of liquid increases, and thus after a time the rate of change of con¬ 
stitution increases too, no doubt again to diminish when the tension given off by the 
film is approaching equilibrium with that in the air. 
Another film (September 29, Y.) was in like manner formed when no precautions 
had been taken to regulate the amount of moisture in the air. When it was about 
11^ minutes old, a dry sheet of blotting paper hung up inside the inner case was 
damped by water introduced by a pipette through the hole in the back of the 
apparatus. The film continued to thin and the electrical resistance to increase, but 
the specific resistance which had been rising immediately began to falh 
In the following table (Table XI.), column I. gives the number of minutes elapsed 
since the formation of the film, column II. the apparent thickness of the part between 
the needles, column III., p, which has the same signification as above. 
The table illustrates the rapid changes which a film may undergo. Similar 
experiments were made with many other films, and always with the same result. 
Table XI. 
l. 
m. 
ii. 
III. 
V■ 
5-6 
14-0 
15-8 
6-4 
13-0 
16-6 
7 -2 
12-0 
16-9 
8-2 
11-0 
177 
9-2 
10-0 
18-5 
107 
9-0 
18-2 
11-2 
Water in 
troduced. 
11-4 
8-5 
17-8 
127 
8-0 
17-3 
12-9 
7-5 
16'5 
13-6 
7-0 
15-6 
14-9 
6*5 
15-0 
16-3 
6-0 
147 
18-0 
5-5 
14-4 
204 
5-0 
13-9 
23-4 
4-5 
13-4 
28*1 
4-0 
12 1 
1 
