Relationships have been determined between film pressure and bulk concentration for dodecyl trimethylammonium bromide and for sodium dodecyl sulphate in a n-heptane/0.1 M aqueous sodium chloride system at 20°C. The results obtained by means of the dipping-plate technique conflict with previously reported results from drop-volume measurements. Relationships between film pressure and area per molecule for adsorbed monolayers were derived by means of the Gibbs equation. Excellent agreement was found for the force-area relations of spread and adsorbed films of the same head-group, confirming the earlier finding that these relations are independent of chain length. The insoluble-monolayer technique thus provides an accurate criterion of the reliability of interfacial tension-concentration data for soluble films.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry