The microscopic structure of semipermeable membranes and the part played by surface forces in osmosis

Abstract

In the following investigation an attempt has been made to arrive at some of the fundamental facts associated with the mechanism of osmosis. Hitherto very few experimental observations have been made in this connection. Raoult, Flusin, Kahlenburg, and a few others have shown, however, that certain membranes such as copper ferrocyanide obeys Poiseuille's law for the rate of flow through capillary tubes; whilst Beutner, Donnan, and others have proved that certain precipitation membranes can act as electrodes, reversible with respect to various ions. The further questions which are dealt with in the present communication are experimental ones: such as what is the size of the colloidal particles of which a semipermeable membrane is composed, and how is the membrane built up from those particles ; to what extent does a membrane show the properties of the gelatinous precipitates or gels as ordinarily prepared by bulk precipitation, and how does its structure differ from these; how is the structure of the membrane altered by variations in the method of its formation, the nature of the solutions bathing it, and the treatment to which it is subjected; and what is the size of its pores, the extent to which they are under the control of surface forces, and therefore of adsorption phenomena also.