Visualization of liquid interface and reaction front flow in partially soluble solvent

Abstract

In this study, visualization of the reaction in partially miscible solvents has been conducted using the Schlieren method, an indicator addition method and PIV method. The CH₃COOH in C₄H₁₀O was set on the NaOH in water against the vertical downward direction of the Hele-Shaw cell. It was found that various convection phenomena could be induced by the generation of H₂O and CH₃COONa during chemical reaction, which were depended on the ratio of initial concentration, R = C_CH3COOH,0/C_NaOH,0. For R = 1, the horizontal travelling wave was observed from the left-hand side to the right-hand side in the HS, which could be caused by Marangoni convection due to the locally H₂O concentration. After that vertical convections were also observed on the interface of the C₄H₁₀O and water and below the interface. They could be caused by Rayleigh Tayler instability and the salt finger, respectively. It was found that the time change of the reaction front from the interface was largely divided by R. For R <1, the change in the reaction front position gradually approaches a constant value in a few seconds. On the other hand, for R≧1, the reaction front increased proportionally t^0.5.