The critical micelle concentration of solutions of cetyltrimethylammonium bromide and of tetradecyltrimethylammonium bromides were determined by a kinetic method. This involved the determination of the rates of the hydroxydehalogenation of some activated aromatic substrates over a wide range of detergent concentrations. Measurements were made in solutions containing significant quantities of added hydroxyl ion and substrates which were themselves amphiphilic. Conventional methods cannot be applied with confidence to such systems. The effects of changing hydroxyl ion concentrations, added sodium bromide, changing the nature of the aromatic substrate (whether neutral or charged), the identity of the micellar counterion and the temperature were investigated. It was wound that added bromide or hydroxyl ions resulted in a lower CMC whereas increased temperature led to an increase in the CMC. The nature of the micellar counterion (Br, F, OH, SO4) had little effect on the CMC. The presence of a charged aromatic substrate led to a considerable lowering of the CMC, whereas the neutral aromatic substrate used showed very little effect.

An investigation of the use of the flow-based procedure of discontinuous flow analysis (DFA) for the determination of silver in photographic emulsions is described. It is shown that a procedure used by the photographic industry which involves the complexation of a silver halide with the thiosulfate ion followed by titration with thioacetamide produces poor repeatability when applied in DFA. Evidence is presented to demonstrate that this is due to a slowing of the response of the silver sensor used to detect the end-point in the titration which is caused by the formation of a loosely bound layer of silver sulfide on the sensor surface. This surface layer has been identified using scanning electron microscopy and cyclic voltammetry. An alternative procedure is proposed for the determination using DFA which involves complexing the silver halide (bromide) with the cyanide ion followed by titration with sodium sulfide. The results from this method are within 2% compared with those obtained by AAS.