Tham khảo tài liệu 'nonlinear dynamics part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 118 Nonlinear Dynamics shorten the induction time. The slight decrease in the induction time observed at a very high bromide concentration may result from decreases in H2Q and BrO3 concentrations due to reactions with bromine. The insensitivity of the induction time to the initial presence of brominated substrates suggests that the governing mechanism of this oscillator may be different from UBOs reported earlier. The influence of Ce4 Ce3 and Mn3 Mn2 It is well known that metal catalysts such as ferroin participate the autocatalytic reactions with bromine dioxide radicals BrO2 and therefore redox potential of the metal catalyst in relative to the redox potential of HBrO2 BrO2 couple is an important parameter in determining the rate of the autocatalytic cycle which in turn has significant effects on the overall reaction behavior. In the BZ reaction four metal catalysts including ferroin ruthenium cerium and manganese can be oxidized by bromine dioxide radicals in which the redox potential of HBrO2 BrO2 couple is larger than that of ferroin and ruthenium but smaller than that of Ce4 Ce3 and Mn3 Mn2 . Therefore it is anticipated that when cerium or manganese ions are introduced into the bromate-pyrocatechol reaction behavior different from that achieved in the ferroin-bromate-pyrocatechol system may emerge. Figure 10 plots the number of oscilllations N and induction time IP of the catalyzed bromatepyrocatechol reaction as a function of catalyst . Ce4 and Mn2 concentration. 0 -I--------------1--------------1--------------1---------------1 0 Cataly st M Fig. 10. Dependence of the number of oscillations N and induction time IP on the initial concentrations of cerium and menganese. Other reaction conditions are H2SO4 M NaBrOs M and H2Q 0 043 M. The sharp increase in the number of oscillations at the low concentration of cerium and manganese illustrates that the presence of a small amount of metal catalyst favours the oscillatory
