VISUALIZATION BY COHERENT ANTI-STOKES-RAMAN SCATTERING SPECTROSCOPY OF THE MIXING PROCESS OF 2 NONREACTIVE LIQUIDS IN A CSTR

By CARS spectroscopy we demonstrate the existence of large concentration variations (fluctuations) during the nonreactive mixing process of two liquids (toluene/p-xylene). The average concentrations of toluene and local fluctuations were measured as a function of position inside a continuous-flow stirred tank reactor (CSTR, 1.5 mL) in five horizontal cross sections with 90 points each. The CARS measurements support the macro- and micromixing concept were the mixing of liquids may be viewed as a stretch-and-fold process of liquid elements. Thus a CSTR represents a "noise generator". These conclusions are also valid for aqueous solutions in which local fluctuations may strongly influence the dynamic behavior of nonlinear chemical reactions.