Contact angles; wetting and de-wetting of mercury: Part I. A critical examination of surface tension measurement by the sessile drop method

A survey is given of the existing methods for measuring the surface tension from the geometry of sessile drops. These methods, which generally consist of the measurement of simple drop dimensions, are insufficiently accurate for use with adsorption studies.

A new procedure is described to find the surface tension by means of a graphical evaluation of the drop shape factor β (the constant shape factor as defined in Bashforth and Adam's treatment of the sessile drop). In this way the accuracy is considerably increased (0.1% uncertainty in γ).

The interfacial tension of the system mercury/0.05 M Na₂SO₄ at −0.460 V vs. saturated calomel electrode, and at 25°, is found to be 426.2 ± 0.2 dynes/cm, which agrees well with the literature.

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