The swelling of isoelectric gelatin in water has been found to be in agreement with the following assumptions.

Gelatin consists of a network of insoluble material containing a solution of a more soluble substance. Water therefore enters owing to the osmotic pressure of the soluble material and thereby puts the network under elastic strain. The process continues until the elastic force is equal to the osmotic pressure. If the temperature is raised or the blocks of gelatin remain swollen over a period of time, the network loses its elasticity and more water enters. In large blocks this secondary swelling overlaps the initial process and so no maximum can be observed.

The swelling of small blocks or films of isoelectric gelatin containing from .14 to .4 gm. of dry gelatin per gm. of water is defined by the equation

See PDF for Equation

in which Ke = the bulk modulus

See PDF for Equation.

Ve = gm. water per gm. gelatin at equilibrium; Vf = gm. water per gm. gelatin when the gelatin solidified.

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Copyright, 1927, by The Rockefeller Institute for Medical Research
1927
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