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The potential response of silver halide membrane electrodes to the corrosive bromous, bromic, iodous, and iodic acids is investigated in sulfuric acid solutions ([HzS04] = 0.15 and 1.5 M), typical media for several well-known oscillating reactions. The syntheses of the materials (bromide-free NaBrOz and HIOJ needed for the experiments are described. The potentials recorded as a function of time were used for the determination or estimation of several rate constants at 24 f 1 "C: the disproportionation rate constant of HBr02 is kgl = (1.4 f 0.2) X lo3 M-' s-l (in 0.15 M HZSO,) and (3.8 f 1.0) x lo3 M-'s-l (in 1.5 M HZSO,); the corresponding value for HIOz is kIl < 5.4 M-' s-l (in 0.05-0.15 M H2S04); the disproportionation of HIO2 is autocatalytic, the rate-determining step is a reaction of HIOz with HzOI+, the rate constant of which is lzI, = 130 f 5 M-' (in 0.15 M HZSO,); the rate constants of the reactions of HBrOz with Br-and H+, and HIOz with I-and H+ are 106 < kg2 < 4 X 106 M-z s-l (in 1.5 M H2S04) and 106 < ItI, < 4 X lo7 M-z s-l ( i n 0.15 M H2S03, respectively.The corrosive reactions of the halous and halic acids with halide ions are much slower than those of hypohalous acids, which fact required the development of the theory for slow corrosive reactions. Criteria for the definitions of "slow" and "fast" corrosive reactions are given. The possibility of a second autocatalytic process in the halate driven oscillating reactions is demonstrated. On the basis of these results, a generalized Lotka-Volterra scheme is proposed for the BZ, BL, and BR oscillators. IntroductionThe present paper is the second communication in a series devoted to studying the potential response of ionselective electrodes to corrosive species in oscillating chemical systems. The ultimate goal of our work is to provide a consistent interpretation of the potential changes displayed by bromide-and iodide-selective electrodes in the course of chemical oscillations, in terms of concentration changes of the several different intermediates involved. As a first step toward that goal, in a previous paper3 we have shown that halide-ion-sensitive electrodes, besides halide ions, also respond to hypohalous acids. Furthermore, we have demonstrated that in the latter case the electrode response can be best explained by the corrosion potential theory (CPT). The corrosion reaction

Electric field-induced transient pore formation (reversible electroporation) in the bilayer membrane of synthetic large unilamellar vesicles (LUV) is used as a novel method for the preparation of angstrom size quantum dots of the indirect band gap semiconductor AgBr. With Ag+ ions encapsulated in 178 nm diameter LUVs of dioleoylphosphatidylcholine (DOPC) and Br- ions placed in the bulk medium, the reaction Ag+ + Br- → AgBr and subsequent clustering of the product are initiated by the application of a 500 μs long high-voltage (E = 6 kV/cm) electric square pulse to the vesicular suspension. The slow growth of clusters (taking several hours) on the exterior surface of the vesicles is monitored through the blue-shift followed by a red-shift of their UV absorption band. At the turn-around point (269 nm) of the spectral band-shift, the size of the AgBr clusters is estimated to be ∼5 Å, the smallest achieved by colloid chemical methods.