The rates of the acid-catalysed hydrolysis of sodium dodecylsulphate (SDS) and sodium dodecyldiethoxysulphate (SDE,S) have been investigated in concentrated surfactant solutions (0.035-0.6 mol dmP3). The acid concentration dependence of the initial rates shows a ' saturation' effect, whereas increasing surfactant concentrations above the c.m.c. lead to a maximum in the kz,obs values, beyond which they decrease sharply.These results are discussed in terms of the ion-exchange pseudophase model of the miceller reaction. The nature of the counterion has an effect on ke+obs, the values following the sequence NH, > Li > Na B Mg. This has been ascribed to differences in the ion-exchange constants, K H I X , of these cations in the Stern layer of the micelles with the hydrogen ion. Maintaining the total counterion concentration and the ratio of concentrations of surfactant counterion to the concentration of hydrogen ion constant (at 30, i.e. 0.6: 0.02 mol dmP3) largely eliminates the decrease in the kz,obs values with increasing surfactant concentration, as expected from the pseudo-phase ion-exchange model. Quantitative agreement between theory and experiment is less good, however, owing at least partly to deviations from ideality in solutions of high ionic strength.

Kinetics of the Acid-catalysed Hydrolysis of Dodec ylsulpha te and D odec yldie t hox y sulpha te Sur fac t an t s in Concentrated Micellar Solutions Part 2.-Effects of Added Electrolytes on the Hydrolysis of Sodium Dodecylsulphate and Sodium Dodecyldiethoxysulphate

Halogeno-o-phenylenediamines and Derived Heterocycles.

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