CONVECTIVE CHEMICAL FRONTS IN THE 1,4-CYCLOHEXANEDIONE-BROMATE-SULFURIC ACID-FERROIN SYSTEM

Traveling waves were investigated in the Belousov-Zhabotinsky reaction in which 1,4-cyclohexanedione was the substrate. Isothermal density c hange (Delta rho(c)) and reaction enthalpy were determined. Delta rho( c) is positive, while the reaction enthalpy is negative; therefore, do uble-diffusive convection was expected according to the Pojman-Epstein model. Experiments were carried out in tubes and in spectrophotometri c cells. In tubes the effect of the diameter and the orientation of th e tube on the wave velocity and on the wave shape was studied; gravita tional anisotropy and the expected double-diffusive convection were fo und. Experiments in cells were compared to the calculations of Wu et a l. (Wu, Y.; Vasquez, D. A.; Edwards, B. F.; Wilder, J. W. Phys. Rev. E 1995, 51, 1119-1127). They predicted a critical cell width under whic h no simple convection should occur. However, because double-diffusive convection was observed, their calculations are not directly applicab le.