General remarks on the nomenclature of charged interfaces

If a unit charge e approaches the surface of an ideally isolated phase (to a distance of approximately 10 cm) from infinity, the work of evg must be done. v / represents the Volta potential. In other words the Volta potential denotes the electrical potential difference inside the phase. 

To transfer charge carriers (electrons, ions) from one phase to another, the surface must be crossed. The surface itself as well as the adsorption layer of surfactants consist of carrying dipoles. That is the reason for an additional jump of the electrical surface potential. This potential may be (Lange 1951) denoted as the dipole part % of the surface potential. 

The simplest model for the electrical double layer is the Helmholtz condenser. A distribution of counterions in the bulk phase described by a Boltzmann distribution agree with the Gouy-Chapman theory. On the basis of a Langmuir isotherm Stem (1924) derived a generalisation of the double layer models given by Helmholtz and Gouy. Grahame (1955) extended this model with the possibility of adsorption of hydrated and dehydrated ions. This leads to a built-up of an inner and an outer Helmholtz double layer. Fig. 2.14. shows schematically the model of specific adsorption of ions and dipoles. 

Example for the Calculation of Potential from Known Dipole Moment of an 

Let us assume the adsorbed surfactant molecule occupy an area of 50A at the interface which corresponds to 2 lO dipoles per cm. We also use the Helmholtz equation 

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