On the product of surface tension and compressibility of liquids

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Abstract
The surface tension γ is inversely proportional to the isothermal compressibility κ, and the product κγ near the triple point is equal to 0.32±0.15 Å for many liquids of dissilimar binding, including liquid metals, molten salts, organic liquids, aqueous solutions, and liquids of the common gases. A semiempirical derivation of this relation is given, in which we use Fowler's formula for γ and two formulas for κ: (1) the scaled‐particle Percus‐Yevick hard‐sphere compressibility formula and (2) the compressibility derived from Carnahan and Starling's equation of state. We find that ρkTκ = 0.04±0.03 for many liquids of dissimilar binding, including the categories mentioned above (ρ = number density). Values of κγ obtained for liquid 4He and liquid 3He extrapolated to 0°K are found to agree with the κγ values of classical liquids.