B Interfacial Parameter and Chemical Structural Effects

We have seen that at some point below but near the CMC the surface becomes essentially saturated with surfactant (F Tm). The relation between y and log C, the Gibbs equation, dy = 23nRT m log C (equation 2.19a), in that region therefore becomes essentially linear. This inear relation continues to the CMC (in fact, it is usually used to determine the CMC). 

From this, we see that the effectiveness of a surfactant in reducing the surface tension of a solvent depends upon  

The number of ions n whose surface concentration changes with change in the liquid-phase concentration of the surfactant  

The larger each of these quantities, the greater the reduction in surface tension attained at the CMC. 

The factors that affect Fm, the effectiveness of adsorption, have been discussed previously (Chapter 2, Section IIIC). We can summarize their effects as follows  

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