The thermodynamic data for the tin‐silver system have been determined by electromotive force measurements on concentration cells involving pure tin and alloys of tin and silver. A technic similar to that developed by Seltz was employed. Activities, relative partial molal and total relative heat contents, free energy changes and entropies are evaluated for both components and for the system over the complete concentration range at 900.1° K. It is shown that solutions of tin‐silver are not “regular” solutions and that the behavior of these alloys is similar to the behavior of the liquid zinc‐antimony alloys.