ABSORPTION OF MOISTURE BY GELATIN IN A SATURATED ATMOSPHERE 325 
An important difference between the curve of absorption as shown for 
gelatin in saturated vapor and that obtained for seeds in water should be 
noted. The absorption curve for Xanthium seeds shows a break at about 
35 percent due to approaching saturation. The gelatin curve here pre- 
sented shows no such break due to approaching saturation, but maintains 
a slowly decreasing rate over long periods of time, with remarkable 
regularity. 
Discussion 
The data which are presented indicate that gelatin absorbs much more 
water from a saturated atmosphere than was found by von Schroder. 
And an examination of his data leads one to suspect that he did not maintain 
a saturated atmosphere. It is not so easy to see in table 2, but in table 3, 
which records the loss of water from saturated gelatin, it is rather easily 
detected. If the behavior in this case were normal, we should find the loss 
largest during the first 24 hours, because the difference in moisture equil- 
ibrium was greatest at the beginning of the experiment. Each day there- 
after should show less and less daily loss because of the closer and closer 
approach of equilibrium conditions. This, however, is not the case in his 
data. On the first day the loss is 0.259 g., on the second day 0.078 g., on 
the third day 0.046 g., on the fourth day 0.035 g., and on the fifth day 0.511 
g. Counting average daily loss, there was nearly twice as large average 
daily loss at the end of five days as at the end of the first four days. And 
at the end of 14 days the average daily loss was still more than double 
that at the end of the first four days. From the fifth day on, the loss is 
always much more rapid than during the second, third, and fourth days. 
This would make it appear very probable that the gelatin was losing water 
into an unsaturated atmosphere. 
And if the atmosphere is unsaturated in this case, it probably was un- 
saturated in the experiments, the data of which are recorded in table 2. 
It is a very difficult matter to produce and maintain conditions of saturation, 
and there is not much doubt that the frequent opening of the chamber for 
weighing allowed the atmosphere to fall considerably below the saturation 
point. There is nothing in von Schroder's discussion to show how he 
handled his materials. Even in our own work we can not be certain 
that complete saturation was procured and maintained at all times. But 
the results would indicate that we came nearer to it than did von Schroder. 
We feel that the amount of work done is insufficient to show that colloids 
do not exhibit the phenomenon to which von Schroder's work called atten- 
tion. Even though we have shown that gelatin takes up from saturated 
vapor much more water than was formerly supposed, it may still be true that 
colloids show a difference in behavior toward water in liquid and in gaseous 
form. Much of the difference in the actual amount of water taken in 
must be related to the filling of minute lacunae when immersed in water, 
and the saturation of the gelatin around the lacunae only, when exposed to 
