THEORETICAL CONSIDERATION ON THE APPLICABILITY OF THE SPHERE METHOD FOR MEASURING INTERFACIAL-TENSION AND CONTACT-ANGLE

When a sphere is passed through the interface between two fluid phases, the interfacial tension as well as the contact angle can be determined by measuring the vertical force components acting on the sphere as a function of the depth of immersion. It is shown that the interfacial tension can be calculated with good accuracy directly from the measured values. This approximation method does not require any numerical solutions of the Laplace equation. From a critical comparison of several methodical variants it is concluded that the sphere method promises good results particularly for larger contact angles. © 1979 Dr. Dietrich Steinkopff Verlag.