326 
CHARLES A. SHULL AND S. P. SHULL 
vapor. The vapor pressure of a saturated colloid may actually be greater 
than that of a flat surface of water, and the colloid be able therefore to 
distil water into the saturated atmosphere which is common to both. 
Whatever the truth may be in regard to this point, it seems to us unfor- 
tunate that a theory of physical chemistry should be based upon a single 
piece of work which shows somewhat gross irregularities in the data, without 
any attempt to confirm the original findings. 
The experience we have had with gelatin in saturated atmosphere, with 
conditions controlled as carefully as possible, at least suggests the desira- 
bility of a reinvestigation of the relation of the vapor pressure of colloids 
to that of the vapor pressure of water, before we try to establish or accept 
theories which attempt to explain this relation. It might be found that 
there is little to explain. 
The University of Kentucky, 
Lexington, Ky. 
LITERATURE CITED 
1. Bancroft, W. D. The action of water vapor upon gelatin. Journ. Phys. Chem. i6: 
396-406. 19 1 2. 
2. Czapek, F. Biochemie der Pflanzen. 2d ed. Vol. i. Jena, 1913. 
3. von Schroder, P. Uber Erstarrungs- und Quellungserscheinungen von Gelatine. 
Zeitschr. Phys. Chem. 45: 75-117. 1903. 
4. Shull, C. A. Temperature and rate of moisture intake in seeds. Bot. Gaz. 69: 361-390. 
1920. 
5. Volbehr, B. F. K. J. Untersuchungen iiber die Quellung der Holzfaser. Kiel, 1896. 
