LII. A new drop-weight method for the comparison of surface tensions

It is shown by dimensional analysis that in the Harkins and Brown drop-weight method of surface- tension determination, the correction factor is a function only of the shape of the unstable drop, provided that when drops are similar in shape at the unstable stage equal fractions of the whole drop become detached. A drop-weight method has been worked out in which the usual flat tip of definite radius is replaced by an inverted cone. It is shown theoretically that all unstable drops hanging from such a cone are similar in shape, and surface-tension determinations may be carried out by this method provided that the cone is calibrated by means of a liquid of known surface tension. The conical-tip method does not require the use of correction factors, and it gives results which are in close agreement with those obtained by the method of Harkins and Brown.