Publication costs assisted by Universitat Bayreuth New developments of the theory of micellar kinetics are reported together with new experimental results obtained in the course of chemical relaxations (T-jump, p-jump, and shock tube) studies of micellar solutions of ionic surfactants. These results as well as those obtained in previous studies are quantitatively interpreted in terms of this theory. Several pieces of information thus far not available on micellar solutions have been obtained: (1) the rate constants k+ and k~for the association/dissociation reactions of one amphiphilic ion to/from micelles. The association reaction is very close to being diffusion controlled. The variation of the dissociation rate constant with the alkyl chain length is in quantitative agreement with what is expected from theory; (2) the width of the distribution curve of stable micelles is found to increase with chain length but the micelle polydispersity is small and decreases for increasing chain length; (3) an approximate value of the average number of amphiphilic ions in the micellar species at the minimum of the distribution curve; (4) the enthalpy and entropy changes associated with the incorporation of one amphiphilic ion into the most stable micelle and into the aggregate at the minimum of the distribution curve. The enthalpy changes for these two processes are of opposite signs. This explains why the overall heat of micellization is very small.

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Time-resolved laser-induced fluorescence is a unique method for direct uranium speciation at low level in the framework of environmental studies. By varying pH and uranium concentration in the absence of carbonate ions and at fixed ionic strength, it was possible, together with free uranyl UO22+, to identify spectrally and temporally all the uranium-hydroxo complexes, namely, UO2OH+, UO2(OH)2, UO2(OH)3−, (UO2)2(OH)22+, (UO2)3(OH)5+, and (UO2)3(OH)7−.

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