In colloidal chemistry, an aggregation number is a description of the number of molecules present in a micelle once the critical micelle concentration (CMC) has been reached. In more detail, it has been defined as the average number of surfactant monomers in a spherical micelle.[1]
The aggregation number of micelles can be determined by isothermal titration calorimetry when the aggregation number is not too high.[2] [3]
Another classical experiment to determine the mean aggregation number would involve the use of a luminescent probe, a quencher and a known concentration of surfactant. If the concentration of the quencher is varied, and the CMC of the surfactant known, the mean aggregation number can be calculated.