New Experiments on Thermoosmosis

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Abstract
Thermoosmosis, the transport of liquid across a membrane which separates two solutions of identical composition but different temperature, was studied by means of a specially constructed apparatus. No thermoosmosis was observed with water or aqueous solutions of nonelectrolytes. With aqueous solutions of electrolytes thermoosmosis occurs across electrically charged membranes but not across uncharged membranes. While thermoosmotic effects are small their reproducibility is good. The rate of thermoosmosis is proportional to the temperature difference across the membrane. The direction of the thermoosmotic movement depends on the sign of charge of the membrane and the nature and concentration of the electrolyte in the solution. The results confirm those of Lippmann and Aubert (1907, 1912) and prove their tentative conclusion that thermoosmosis with electrolytic solutions is an electrochemical phenomenon and related to electroosmosis. The present results show in addition that the direction and rate of thermoosmosis depend in a strikingly similar manner on those factors which determine the direction and rate of anomalous osmosis, namely, the charge of the membrane and the nature and concentration of the electrolyte. This similarity is strongly suggestive evidence of a fundamental, close relationship between the two phenomena.

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