Adsorption of hydrogen sulfide at the aqueous solution interface. [Pressures up to 3. 0 MPa; 25--130/sup 0/C]

The surface tension of H/sub 2/S-saturated water has been measured at pressures up to 3.0 MPa and at temperatures within the range 25 to 130/sup 0/C. Monolayer coverage of the surface of the aqueous solution by H/sub 2/S occurred at about one-half the saturation pressure, P/sub s/, of liquid H/sub 2/S at a given temperature. Multilayer condensation increased significantly as P/sub s/ was approached. Interfacial tensions between liquid H/sub 2/S and aqueous H/sub 2/S solutions were measured between 30 and 40/sup 0/C. These data were used to show that the spreading coefficients, S/sub 2/, for liquid H/sub 2/S on water were positive and that liquid H/sub 2/S spread on the aqueous phase. The standard thermodynamic properties for the adsorption of H/sub 2/S on water were calculated at the zero-coverage limit between 25 and 130/sup 0/C. The unusually high adsorption coefficient for H/sub 2/S on water was found to be due to a large, positive entropy of adsorption.