THE STRUCTURE OF T H E COLLODION MEMBRANE AND ITS ELECTRICAL BEHAVIOR IX. WATER UPTAKE AND SWELLING OF COLLODION MEMBRANES IN AQUEOUS SOLUTIONS OF ORGANIC ELECTROLYTES AND NON-ELECTROLYTES BY KARL SOLLNER Am)

In a recent publication Carr and Sollner 1 have reported on the water uptake and the swelling of collodion membranes in water and solutions of strong inorganic electrolytes. They determined the weight and volume changes of collodion membranes when placed in water and when transferred from water to solutions of strong electrolytes. I t was found that dried collodion membranes swell reversibly to an appreciable extent when placed in water, the swelling varying from 5 to 11 per cent depending on the brand of collodion. The water uptake as determined by the weight increase is larger than could be accounted for by the volume increase, swelling accounting for only 60 to 70 per cent of the water taken up by the membranes. When the "water-wetted dried" collodion membranes were transferred from water to solutions of various strong electrolytes, there was no detectable change in volume. Similarly, when "porous" membranes were transferred from water to solutions of strong electrolytes, there was no significant volume change. Without giving further details, Carr and Sollner I stated that the problem of water uptake and swelling of collodion membranes is more complex in aqueous solutions of many organic compounds. This is of interest in view of the fact that the permeability of collodion membranes to various organic substances in aqueous solutions was found by several investigators to be anomalously high. Michaelis and Fujita 2 reported that strychnine, quinine, and other alkaloid cations penetrate dried collodion membranes with approximately the same ease as do sodium ions, which undoubtedly are much smaller. Collander, s measuring the relative permeability of about thirty organic nonelectrolytes and weakly dissociated compounds, mostly acids, found that with a few exceptions the permeability decreased regularly with increasing molecular