M. A. Mcgregor, G. T. Barnes
Nov 1, 1977
Citations
0
Influential Citations
15
Citations
Journal
Journal of Colloid and Interface Science
Abstract
Equilibrium surface pressure-area isotherms for sodium docosyl sulfate (NaDS) have been measured on substrates containing various concentrations of hexadecyl-trimethyl-ammonium bromide (CTAB); and from the isotherms, the saturation adsorptions of CTAB for various surface concentrations of NaDS have been calculated. The surface pressure-area data and other results indicate that a complex is formed in the surface consisting of two NaDS molecules for each CTAB molecule. The Gibbs equation has been modified to account for the presence of the complex on the surface, and adsorptions calculated from this equation are somewhat lower than values calculated without allowing for complex formation. The plot of adsorption against the inverse of the area per NaDS molecule is linear, as required by the accessible area theory. This plot yields a value for the adsorption into accessible areas of the surface that corresponds to the adsorption of CTAB at a monolayer-free surface. However, the other parameter derived from the theory, the effective area of a monolayer molecule, corresponds to the area of the 2:1 surface complex rather than the area of a NaDS molecule.