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Title: A new B-Z oscillator with a modified control mechanism
Authors: Rastogi, R P
Khare, Ravi
Misra, G P
Srivastava, Sangita
Issue Date: Jan-1997
Publisher: NISCAIR-CSIR, India
Abstract: Oscillations in fructose + BrO3- +Ce++ + H2S04 system without any bromine scavenger have been observed in the range 0.035-0.7 M fructose in a batch reactor as well as continuous stirred tank reactor (CSTR). Analysis of reaction product was done by TLC, UV, NMR and HPLC. The oscillations are insensitive to Br- concentration even up to 10-2 M. [Br -] and lBr2] have been estimated at several stages of oscillations in a typical case. At the maxima, [Br -] is found to be of the order of 10-5, M which is much higher than the critical Br - concentration. Tartaric acid is found to promote oscillations when added to non-oscillating fructose system although no oscillations are observed in tartaric acid + BrO3-; + Ce ++ + H2S04 system of a similar concentrations. Within a certain range -of fructose concentration, damped complex oscillations are observed in the batch reactor. In CSTR a periodic oscillations are observed at higher [fructose] with decreasing now rates although sustained periodic oscillations are observed at low [fructose]. In a particular concentration range two types of oscillations in fructose (F) + acetone oscillator separated by time pause have also been observed in the batch reactor. Oscillations that occur before time pause (first type oscillations) are insensitive to addition of Br up to 10- 2 M and are similar to that observed in the corresponding fructose oscillator without acetone. On the other hand. oscillations that occur after time pause (second type oscillations) are stopped when [Br -] ≈ 10-2' M. The colour of reaction mixture is intense brown during first type of oscillations. It changes from colourless to yellow during second type of oscillations. At higher concentration of fructose, only oscillations observed before time pause are obtained while at lower concentration of fructose only the oscillations observed after time pause are obtained but in between sequential oscillations are observed. Computer simulation studies have also been undertaken. Br- -control mechanism is unable to predict oscillations as such, whereas a mechanism based on free-radical control as well as Br- " -control predicts oscillations. Polymerisation studies and ESR studies have been undertaken to ascertain the formation of free radicals.
Page(s): 19-30
ISSN: 0975-0975(Online); 0376-4710(Print)
Appears in Collections:IJC-A Vol.36A(01) [January 1997]

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