Tolman's δ, surface curvature, compressibility effects, and the free energy of drops

An extension of a treatment by Laaksonen and McGraw leads to an analytical expression for the variation of Tolman's delta with drop size. According to this approach, the change in sign of delta as a drop becomes large is a consequence of compressibility. An expression for the reversible work to produce a small drop from bulk liquid is given that corrects conventional expressions for effects of compressibility and Tolman's delta. It is shown, however, that when this expression is applied to the formation of a drop from the supersaturated vapor, the reversible work, W-rev', in excess of volume work no longer explicitly involves the Tolman delta or the compressibility, in agreement with treatments by Gibbs and by Debenedetti and Reiss. Nevertheless, if the expression for W-rev' is to be related to directly measurable quantities, compressibility and delta still play a role.