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Gibbs isotherm is an equation which could be considered an adsorption isotherm that connects surface tension of a solution with the concentration of the solute. Substances can have different effects on surface tension:
Additional recommended knowledge
Gibbs isotherm is
Therefore inorganic salts have negative surface concentrations (which is logical, because they have strong attractions with the solvent) and surfactants have positive surface concentrations: they adsorb on the interface.
A method for determining surface concentrations is needed in order to prove the validity of the model: two different techniques are normally used: elipsometry and following the decay of 14C present in the surfactant molecules.
Gibbs isotherm for ionic surfactants
Ionic surfactants require special considerations, as they are electrolytes:
ΓS refers to the surface concentration of surfactant molecules, without considering the counter ion.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Gibbs_isotherm". A list of authors is available in Wikipedia.|