Growth of Sodium Dodecyl Sulfate Micelles with Detergent Concentration

Sodium alkyl sulfate micelles are predicted to grow as a power law of the total counterion salt concentration, Yaq, in the aqueous phase as follows: NA = K~(Y~~)Y, where N A is the micelle aggregation number and ~2 and y are constants which are estimated from the critical micelle concentration and the apparent degree of counterion attachment. For sodium dodecyl sulfate, NA = 162(Y,q)1/4 is predicted and is shown to be in good agreement with aggregation numbers measured by a number of techniques over a wide range of Yaq whether this quantity is varied by changing the concentrations of the detergent, the added counterion salt, or both. Values of ~2 and y are estimated for six members of the sodium alkyl sulfate family.