The tension of composite fluid surfaces.—No. II

Abstract

With the figures in Table III of the preceding paper (p. 311) as a guide the problem of the spreading of one fluid over the surface of another may be approached with some sense of security. In an earlier paper the equation of a composite surface was found to be T S = T A + T AB -K g when T S is the tension of the composite surface, and K g a term depending upon gravity. Putting K g = 0, it is seen that spreading will occur only when T S > T A + T AB , and, at the limit, T S =T B that is to the tension of pure water in the experiments under consideration. Taking T B = 74, the tension of pure water, we have from the last paper That is to say a drop of any of these saturated substances should not spread upon a surface of pure water except octane, and in actual fact none of them do spread, except octane, a drop of which slowly expands on water to form a very thin plate. In the case of all the other substances examined the quantity (T A + T AB ), < T B , and they all flash over a water surface in characteristic fashion.