Abstract
We describe an improved Taylor dispersion method for four-component systems, which we apply to measure the main- and cross-diffusion coefficients in an Aerosol OT water-in-oil microemulsion loaded with one of the reactants of the Belousov−Zhabotinsky (BZ) reaction, water(1)/AOT(2)/R(3)/octane(4) system, where R is malonic acid or ferroin. With [H2O]/[AOT] = 11.8 and volume droplet fraction φd = 0.18, when the microemulsion is below the percolation transition, the cross-diffusion coefficients D 13 and D 23 are large and positive (D 13/D 33 ≅ 14, D 23/D 33 ≅ 3) for malonic acid and large and negative for ferroin (D 13/D 33 ≅ −112, D 23/D 33 ≅ −30) while coefficients D 31 and D 32 are small and negative for malonic acid (D 31/D 33 ≅ −0.01, D 32/D 33 ≅ −0.14) and small and positive for ferroin (D 31/D 33 ≅ 5 × 10−4, D 32/D 33 ≅ 8 × 10−3). These data represent the first direct determination of cross-diffusion effects in a pattern-forming system and of the full matrix of diffusion coefficients for a four-component system. The results should provide a basis for modeling pattern formation in the BZ−AOT system.