The Szyszkowski, Langmuir, and Frumkin Equations

In addition to the Gibbs equation, three other equations have been suggested that relate the surface excess Tj, surface or interfadal tension and equilibrium concentration in the liquid phase C . The Langmuir equation [3] relates Tj to Cj 

Equation (5.28) shows that a plot of 1/Tj versus 1/Cj gives a straight line from which F and a can be calculated from the intercept and slope of the line. 

The S2yszkowski equation [4], which indicates a relationship between the surface pressure and bulk surfactant concentration Cj, is a form of equation of state  

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