The effect of electrolyte on the micellar charge and hydration of a polyoxyethylene sulphate type of detergent in aqueous solution

Summary Measurements of the electrophoretic mobilities of the micelles of the anionic detergent C₁₆H₃₃(OCH₂ · CH₂)₇OSO₃Na have been made in aqueous sodium chloride solutions over the concentration range 0-0.01 M and used to calculate the magnitude of the electroviscous effect and the micellar charge in these solutions. The micellar hydration, as assessed from viscosity data, is shown to decrease as the salt concentration is increased and this is thought to be a consequence of the lower micellar charge in the more concentrated salt solutions which allows a greater contraction of the ethylene oxide chains resulting in a loss of water mechanically trapped by the micelles.