title: Calculation of contact angles from surfactant adsorption isotherms.
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.
authors.affiliation: steve.chwastiak@alum.mit.edu
authors.forename: Stephen
authors.initials: S
authors.lastname: Chwastiak