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Many different clock reactions have been reported in the student experiment literature (1-14). Clock reactions do not require instruments and are also quick enough so that many variations (temperature, concentration, ionic strength) can be studied in a single period. The major disadvantage is that in almost all cases there is a long period in which nothing appears to happen, followed by a sudden dramatic change, which gives the student the unrealistic idea that the reaction begins suddenly after an induction period. The chemistry is also necessarily complicated since at least two reactions are involved.The system we report can be conveniently studied by clock reaction methods with the added advantage that there is a continuous change in color until the sample matches a control. This eliminates the pedagogical difficulties of traditional clock reactions. This reaction is the bleaching of bromcresol green (BCG) by hypochlorite. There is a fast reaction, which is followed in this experiment, and a slow reaction in which a colorless product is produced overnight. The fast reaction involves the change of color from the blue basic form of the dye to a yellow intermediate.Since BCG is an acid-base indicator, it has both an acid form (yellow) and a basic form (blue): basic acid

274ChemInform Abstract In order to mimic intramolecular electron transfer in protein systems, models such as (V) are prepared by Zn-mediated, acid-catalyzed coupling of (III) with (IV) and subsequent oxidation (no yields are given). The mixed Fe2+-(Va)-Fe3+ system undergoes fast electron exchange under conditions in which bimolecular electron transfer is minimal and the diporphyrin reacts many times faster than a similar protein-protein system. (Fluorescence quenching).