It was found from experiments that the addition of polythylene glycol (PEG) can make the B-Z and B-R reactions producing double induction periods, i.e. before the general induction period there is an earlier stage of induction in which there is no any change of color and state. The lifetime of the earlier stage is not noly effected by the concentration of PEG, but also by the time of the last reagent added. It was also found that there are two linear relationships between the concentration of PEG and the reduced viscodity of PEG solution or/and the lifetime of the earlier stage of induction. Another characteristic of PEG effect is that it can decrease the period change during the oscillat ing reactions. These experimental results are not only useful in the research pf chemical oscillation, but also give a simple method for determining colligative properties of macro molecule sultion.
