An examination of the basic postulates of surface chemistry: A variational calculus analysis of the classic rotating drop experiment

A demonstration, using the variational calculus, is given showing that it is impossible to describe the excess free energy in any liquid surface by the use of a single energy parameter, the surface tension, without violating the laws of motion. The addition of the required second parameter, the flexural rigidity, is shown to be adequate to explain published data on the systemn-hexadecane/glycerol, and to demonstrate that for small radii of curvature, the curvature parameter may contribute orders of magnitude more to the surface energy than the surface tension does.