The Measurement of Low Interfacial Tension via the Spinning Drop Technique

Introduction A method for obtaining interfacial and surface tensions by measuring the shape of a drop of liquid or bubble of gas in a more dense liquid contained in a rotating horizontal tube was first suggested by Plateau's (1) experiments. Beer (2) in 1855 considered the problem of the shape of the drop in some detail, as did Lord Rayleigh (3) in 1914. It was not until 1942, however, that Vonnegut (4) suggested the method be used for measuring surface and interfacial tensions. Vonnegut's method rested on the approximation that the drop could be treated as a cylinder with hemispherical ends and thus avoided having to solve exactly for the drop shape. The diameter of the cylinder was the sole dimension of interest used to calculate the tension. Silberberg (5) improved Vonnegut's method by calculating correction factors for low speeds or small volumes. Rosenthal (6) in 1962 considered the stability