The properties of dry collodion membranes previously described allow the prediction that cells of these membranes will concentrate solutes under certain conditions. Three such cases have been studied experimentally.
1. A membrane containing thiosulphate and immersed in a solution of iodine concentrates iodide ion.
2. A membrane containing sodium chromate and immersed in mercury chloride concentrates chloride ion.
3. A membrane containing calcium carbonate and immersed in acetic acid concentrates acetate ions.