(1953). New Experiments on Thermoosmosis

Thermoosmosis, the transport of l iquid across a membrane which separates two solutions of identical composition but different emperature, was studied by means of a specially constructed apparatus. No thermoosmosis was observed with water or aqueous olutions of nonelectrolytes. With aqueous olutions of electrolytes thermoosmosis occurs across electrically charged membranes but not across uncharged membranes. While thermoosmotic effects are small their reproducibil ity is good. The rate of thermoosmosis is proportional to the tem-perature 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 L ippmann 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 di-rection and rate of thermoosmosis depend in a strikingly similar manner on thos