INTERFACIAL-TENSION IN BINARY-SYSTEMS CONTAINING A DENSE GAS

An experimental system was constructed consisting of an autoclave, a d evice for measuring interfacial tension using the pendant-drop method, and a density-measuring device was constructed. Interfacial tension w as measured at pressures up to 25 MPa and temperatures ranging from 31 3 to 393 K. Furthermore, the density of the coexisting phases and phas e equilibria were measured. The investigated binary systems are compos ed of pelargonic acid or stearic acid as nonvolatile components and ca rbon dioxide, ethane, nitrogen, argon, helium, or hydrogen as gaseous components. The interfacial tension was found to be mainly a function of the gas content of the coexisting liquid phase. Except for helium, the interfacial tension decreases with increasing gas concentration of the liquid phase. At equal gas content in the liquid phase, carbon di oxide and ethane, having positive heat of solution, decrease the inter facial tension less than argon and nitrogen, having negative heat of s olution. The influence of hydrogen on the interfacial tension does not fit in this order because of its very small size.