Caloric Behavior of Chemical Oscillation Reactions Shuko Fujieda (Received December 16, 1996) Chemical oscillation behavior of Belousov- Zhabotinskii (BZ) and Briggs- Rauscher (BR) reactions was followed by heat exchange calorimetry of batch and flow types. The chemical oscillations were observed in the solutions composed of bromate, sulfuric acid, malonic acid and Ce(IV) salt for BZ reactions, and hydrogen peroxide, iodate, sulfuric acid, malonic acid and MnSO4 for BR reactions. The concentrations of bromide and iodde in the BZ and BR reactions, respectively, were also monitored simultaneously by the usual potentiometric cell incorporated in the heat exchange calorimeter. The reaction mechanism was discussed in the relation of the observed total heat effect, heat evolving rate and potential difference, and oxygen volume released in BR reactions.
Fig. 1 Analog computation circuit. Netsu Sokutei 24 (1) 1997 5
Table 2 Certification of the assembled calorimeter. Errors in % of standard deviation estimated by Joule heat. Table 3 Mechanism for the BZ Reaction3), so called Field- Koros-Noyes Mechanism.
Fig. 5 Influence of the variation of [Ce(IV)]0 on the observed q plotted versus time: (a) 0.600mM; (b) 0.999mM; (c) 2.13mM; (d) 4.00mM. Fig. 6 Q VS. t (A) and E VS. t (B) in the flow system at Vs=2.90cm3min-1 (t=1053s), [Ce4+]0=1.00 mm, [MA]0=0.300M, [BrO3-]0=0.140 M and [H2SO4]0=0.200M. Fig. 7 Comparison of Q VS. t and E VS. t curves in observed in flow and batch operations. [Ce4+]0=1.00mM, [MA]0=0.300M, [BrO3-]0 =0.140M and [H2SO 4]0=0.200M. Netsu Sokutei 24 (1) 1997 9
Fig. 8 Typical curves observed against time for the BR reaction in the solution composed of [H2O2]0=1.0M,[KIO3]0=0.040M,[MnSO4]0= 0.010M, [H2S0O4]0=0.020 M and [MA]0=0.040 M. E, potential difference; Q, total heat; q, heat evolving rate; G, oxygen evolving rate. At 1min after the addition of an aliquot of solid MA to start the reaction. q, heat evolving rate. (1) is calculated from Ref. 22. Fig. 9 One cycle of oscillation to compare E and q against time. The initial concentration, [H2O2]0=0.72M, [KIO3]0=0.041M, [MnSO4]0 =0.0040 M, [H2SO4]0=0.0036M and [MA] 0= 0.060M. E, potential difference; Q, total heat; 10 Netsu Sokutei 24 (1) 1997
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