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Updated: Jun 20, 2026

Accurate Determination of the Equilibrium Surface Tension Values with Area Perturbation Tests
Published on: August 30, 2019
Calculation of contact angles from surfactant adsorption isotherms
1steve.chwastiak@alum.mit.edu
Abstract:
Wetting in the system hematite-water-diisobutyl ketone was studied in the presence of an anionic surfactant, hexadecyl sulfonic acid. Adsorption isotherms of surfactant on hematite powder were measured separately at the interfaces between hematite-water and hematite-ketone, and the interfacial tension of the water-ketone interface was determined as a function of surfactant concentration. The Gibbs and Young's equations were used to calculate contact angles from the adsorption data. For comparison, contact angles were measured as a function of surfactant concentration on the face of a hematite crystal selected from the same supply of specular hematite used for preparing the hematite powder. Overall, contact angles calculated from the equations correlate closely with measured contact angles.
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