Structure of T H E Collodion Membrane and Its Electrical Behavior Vi

Previous publications 1, ~ in this series have dealt with the preparation and electrochemical properties of the activated (electronegative) collodion membrane. The activation consisted of an oxidation of the nitrocellulose, a process which caused an increase in the number of dissociable groups in the pores of the membrane. Such membranes show more pronounced effects than similar untreated membranes when tested by electrochemical methods such as the extent of anomalous osmosis, the magnitude of concentration potentials, and the rate of electroosmosis. The purpose of the present communication is to present a method for the preparation and a description of electropositive membranes which are analogous in most respects to the activated collodion membranes. The literature on electropositive membranes has recently been reviewed by Manegold and Kalauch? Two general methods for the preparation of such membranes are available. First, they have been prepared from inherently electropositive materials, such as the oxides of aluminum, zirconium, or thorium.4, s The second method consists of'impregnating membranes prepared from collodion or similar materials with some basic organic compound. One objection to the use of the polyvalent metal oxide membranes is that the electropositive charge is rather easily reversed in the presence of many electrolytes. For this reason they are not suitable for most purposes. The impregnated membrane, in many instances, has proven more practical. The impregnation of collodion with basic substances may be accomplished either by dissolving such substance in the collodion solution or by adsorbing the material on the surface of a previously cast membrane. Among the