Abstract:

The relations between preoscillatory period τ as well as oscillating period T_2 and each reactant initial concentration have been studied. The formula at 302K are:
τ=22.8 c~(-2.23)_(H_2SO_4) c~(-2.17)_(KBrO_3) c~(0.795)_(GA) (mol.dm~(-3))~(4.25)·s
T_2=0.84 c~(-2.28)_(H_2SO-4)c~(-1.97)_(KBrO_3) exp{(0.000147(mol.dm~(-3))~2/c~2_(GA)}(mol.dm~(-3))~(4.25)·s
The major conclusions are:
(1): τ and T_2 decrease while increasing concentrations of KBrO_3 and H_2SO_4, which is similiar to classical BZ systems(1).
(2):τ and T_2 increase with increasing the concentration of GA (Gallic Acid), which is contrary to the classical BZ systems. This implies that organic subtrate GA plays special rule in the oscillation of GA-KBrO_3-H_2SO_4 system.
With the method of CV(Cyclic Voltammgrams) the effects of GA in this system have been studied. It has been found that when preoscillatory period ends GA is almost exhausted. In other word, It is impossible to hold oscillation of this system with GA subtrate. In fact, GA subtrate only supplies the substances that hold oscillation of this system. Therefore, The explanation of OKN mechanism~([4]) to this system is not available.
It has been studied that the effects of Fe(Phen)~(2+)_3 on the oscillation of GA-KBrO_3-H_2SO_4 system. It has been found that the oscillating behavior of Br~- ion will change with the concentration of Fe(Phen)~(2+)_3, ie, at low concentration of Fe(Phen)~(2+)_3 the behavior of Br~- ion is similiar to that of GA-KBrO-H_2SO_4 system, at high concentration of Fe(Phen)~(2+)_3 the behavior of Br~- ion is contrary to that GA-KBrO_3-H_2SO_4 system. The significant differenc es are that before the oscillating pulse of Br~- ion during each oscillating period the former is gradual increase of Br~- ion concentration and the latter is gradual decrease of Br~- ion concentration. The kind of phenomenon in chemical oscillations is first discovered. This implies that the oscillation of GA-KBrO_3-H_2SO_4-Fe(phen)~(2+)_3 system cannot be explained with OKN mechanism. The oscillation is phenomenally couple of two different oscillations.