EXPERIMENTAL-STUDY OF A CROSSOVER FROM NONCLASSICAL TO CLASSICAL CHEMICAL-KINETICS - AN ELEMENTARY AND REVERSIBLE A--]C REACTION-DIFFUSION PROCESS IN A CAPILLARY(B[)

We study an elementary and reversible A+B<->C reaction-diffusion proce ss with initially separated reagents, in a convectionless capillary, u sing an inorganic chemical reaction. We show that the dynamics of the system can be described in terms of a crossover between an ''irreversi ble regime'' and a ''reversible regime.'' We measured the critical exp onents in both regimes. In the irreversible regime we demonstrate the nonclassical phenomena of reactant segregation and depletion-zone form ation. In the reversible regime we observed the effect of a local equi librium where the classical prediction is confirmed. The experimental results are in good agreement with values predicted by theory and simu lation.