ABSORPTION OF MOISTURE BY GELATIN IN A SATURATED ATMOSPHERE 32 1 
and these sheets were cut into disks before they became entirely dry, while 
still slightly pliable, and the disks were dried out in contact with air until 
weight loss ceased. During this preparation the gelatin was carefully 
protected from dust to reduce chances of mold or bacterial infection. 
The disks were exposed to a saturated atmosphere in small wide- 
mouthed bottles. The bottles were arranged with a layer of mercury in 
the bottom sufficient to sink them. Over the mercury was a layer of water. 
The gelatin disks were suspended over the water, just as near the water 
surface as practicable, in shallow paper baskets which were attached by 
threads and wax to the center of the rubber cork which closed the bottle. 
The rubber cork was shellacked upon its inner and outer surfaces to protect 
it from water, probably an unnecessary precaution. 
To control the temperature the bottles were sunk in a Freas thermostat 
which was set to run at 26° C, and which showed no deviation with an 
ordinary chemical thermometer during the five months while the tests 
were run. It was found necessary to control the growth of bacteria and 
molds on the gelatin, and this was accomplished by the use of small pieces 
of thymol in the water. The bottles were usually placed in the thermostat 
for some time before the gelatin was introduced. This allowed the air to 
become more nearly saturated. Then the weighed disks were put into the 
baskets. At intervals which were purposely made infrequent so as not to 
interfere with the saturation of the air, the disks were removed carefully 
and quickly to weighing bottles and weighed. The greatest care was taken 
to keep the disks from drying out during weighing, and to keep the air to 
which they were exposed during intake intervals from becoming unsaturated. 
The bottles were always corked and returned to the thermostat during 
weighings. It was noted that there was always condensation of vapor 
on the walls of the. weighing bottles, so that it was not possible to prevent 
all losses of water. 
Results 
In all cases it was found that much more water was absorbed by the 
gelatin from the atmosphere than von Schroder had observed. During the 
preliminary tests in one instance there was a regular intake of water which 
continued for weeks, and which had reached an intake of 250 percent of the 
weight of gelatin when it was accidentally overturned by the laboratory 
attendant, and the experiment was thus brought to an abrupt end. A 
considerable number of disks were started, some with and some without 
thymol. The rate of intake was apparently about the same during the 
first several days, but the disks exposed without thymol would always 
suffer in time with bacterial or mold infections. Usually after about three 
days the uncontrolled disks had to be discarded. The indications were that 
the thymol itself was not noticeably accelerating the rate of water intake. 
Plotted curves practically coincided during the first several days, with and 
without control. 
