Chemo-Hydrodynamical Instability Created by CO2 Absorption in an Aqueous Solution of NaHCO3 and Na2CO3

CO₂ absorption in an initially quiescent aqueous solution of NaHCO₃ and Na₂CO₃ is studied in a Hele-Shaw cell. Using a Mach-Zehnder interferometer, refractive index variations in the liquid are followed during the absorption. It is shown that chemo-hydrodynamical instabilities appear in the liquid phase below the interface. A description of the observations and a preliminary simple modeling of this instability is presented in this paper. It is found that the conjecture that the Rayleigh-Taylor mechanism takes part in triggering the convection is not incompatible with the observed behavior.