ABSORPTION OF MOISTURE BY GELATIN IN A SATURATED 
ATMOSPHERE! 
Charles A. Shull and S. P. Shull 
A great deal of work has been done to determine the relation of colloidal 
matter to water, gelatin being a favorite substance for such studies. How- 
ever, one finds but few attempts to determine the water relations established 
when the colloidal material is exposed to an atmosphere saturated with 
water vapor. The earliest observations of a difference in behavior of 
colloids toward water and water vapor are credited to Volbehr (5). The 
main work dealing with this subject is a paper by von Schroder (3), who 
claims that gelatin absorbs much more water when placed in liquid water 
than when exposed to a vapor-saturated atmosphere. The data presented 
in his paper were afterwards used as a basis for a theoretical discussion by 
Bancroft (i), who attempted an explanation of the observed phenomena, 
but without any apparent attempt to verify von Schroder's results. One 
finds in the recent literature occasional reference to these papers, as in 
Czapek (2). Here Czapek (p. 42) adopts Bancroft's explanation of the 
supposed difference between the vapor pressure of the colloid and that 
of the mass of water which saturates the atmosphere about the colloid. 
For the sake of clearness it will be advantageous to state briefly the 
results of von Schroder's investigations as given in section VII of his paper, 
which is entitled "Ein Beitrag zur Thermodynamik der Quellung" {I.e., 
pp. 109-117). 
In the first place, gelatin absorbs water very rapidly from liquid water. 
A piece of gelatin weighing 0.801 g., and which contained 17.6 percent of 
hygroscopic water, took up moisture as shown in table I . 
Table i . A hsorption of Water hy Gelatin from Liquid Water 
Time Intake in Grams Gain Percent* 
5 mins 2.282 336.1 
10 mins 2.934 432-1 
20 mins 3.669 540.3 
30 mins 4.072 599-7 
40 mins 4.300 633.3 
50 mins 4-415 650.2 
60 mins 4.506 663.6 
2 hrs 4.941 727.7 
24 hrs 6.911 1018. 
48 hrs 7.734 1039. 
* Calculated on absolute dry weight of gelatin disc, 0.679 g. 
1 Contributions from the Botanical Laboratories of the University of Kentucky, No. 3. 
318 
