Spinning drop tensiometry using a square section sample tube

When measuring interfacial tensions, conventional spinning drop tensiometry requires knowledge of the index of refraction of the denser, outer fluid p hase, in order to correct for the magnification of the inner, spinning drop . We have modified a spinning drop tensiometer to accommodate a square sect ion sample tube, which does not require this correction. Tests performed us ing calibration rods are used to demonstrate this fact. The interfacial ten sion of toluene and water is also measured using this new design. The ensui ng results are in agreement with measurements obtained using a conventional circular sample tube. (C) 2001 Academic Press.