Convection-Induced Fingering Fronts in the Chlorite–Trithionate Reaction

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 120; no. 16; pp. 2514 - 2520
• Main Authors: Liu, Yang, Zhou, Wenxiu, Zheng, Ting, Zhao, Yuemin, Gao, Qingyu, Pan, Changwei, Horváth, Attila K
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 28.04.2016
• Subjects: Buoyancy; Computer simulation; Consumption; Density; Instability; Mathematical analysis; Propagation; Stability
• ISSN: 1089-5639; 1520-5215; 1520-5215
• DOI: 10.1021/acs.jpca.6b01192

Based upon a former study, the chlorite–trithionate reaction can avoid the side reactions arising from the well-known alkaline decomposition of polythionates, making it a suitable candidate for investigating spatial front instabilities in a reaction–diffusion–convection system. In this work, the chlorite–trithionate reaction was investigated in a Hele-Shaw cell, in which fingering patterns were observed over a wide range of reactant concentrations. A significant density increment crossing the propagating front indicates that the fingering pattern is generated as a consequence of the buoyancy-driven instability due to the density changes of solute when the gap thickness is less than 4 mm. The velocity of the steepest descent in the propagating front depends almost linearly on the gap thickness but displays a saturation-like profile on the trithionate concentration as well as a maximum on the chlorite concentration. Numerical simulation using the Stokes–Brinkman Equation coupled to the reaction–diffusion processes, including hydrogen ion autocatalysis and consumption, reproduces the observed fingering fronts.