By using labelled sodium sulfate or calcium sulfate (sulfate containing S(35)) the transition of sulfate ion into the body across the skin was investigated soon after taking a bath in sodium
sulfate or calcium sulfate solution under varing conditions. Mice were used for experiments. The percutaneous absorption of sulfate ion proved to decrease gradually in the course of serial baths in sodium sulfate solntion and was accelerated by making a fresh burn on the skin of the bathed animals, but it showed a tendency to decrease as the wound became more and more healed. The application of basic dye to the skin (e.g. 1% methylenblue or 1% fuchsin solution) increased the transition of sulfate ion into the test animal. Little difference was proved between the bath in sodium sulfate and calcium sulfate solution with respect to the penetration of sulfate ion. Passage of sulfate ion from the bath water through the skin was a little promoted by the use of sodium sulfate solution than by the use of calcium sulfate solution.