Abstract
A general equation ('isotherm') is derived for the adsorption of long-chain ions from water to air or oil interfaces. Under various limiting conditions this general adsorption equation reduces to the Langmuir, Kuster (Freundlich) or Temkin isotherms. Recently published experimental data agree satisfactorily with the theory of this paper, over a wide range of concentration of sodium lauryl sulphate and its near homologues, both with and without added sodium chloride.