Issue 38, 2011
From the journal:

Physical Chemistry Chemical Physics

Differential diffusion effects on buoyancy-driven instabilities of acid–base fronts: the case of a color indicator

S. Kuster,a   L. A. Riolfo,ab   A. Zalts,c   C. El Hasi,c   C. Almarcha,b   P. M. J. Trevelyan,b   A. De Wit*b  and  A. D'Onofrio*a  

* Corresponding authors

a Grupo de Medios Porosos, Facultad de Ingeniería, Universidad de Buenos Aires, Paseo Colón 850, Buenos Aires, Argentina
E-mail: adonofr@fi.uba.ar

b Nonlinear Physical Chemistry Unit, Service de Chimie Physique et Biologie Théorique, Université Libre de Bruxelles (ULB), Campus Plaine, 1050 Brussels, Belgium
E-mail: adewit@ulb.ac.be

c Instituto de Ciencias, Universidad Nacional General Sarmiento, J. M. Gutiérrez 1150, B1613GSX, Los Polvorines, Provincia de Buenos Aires, Argentina

Abstract

Buoyancy-driven hydrodynamic instabilities of acid–base fronts are studied both experimentally and theoretically in the case where an aqueous solution of a strong acid is put above a denser aqueous solution of a color indicator in the gravity field. The neutralization reaction between the acid and the color indicator as well as their differential diffusion modifies the initially stable density profile in the system and can trigger convective motions both above and below the initial contact line. The type of patterns observed as well as their wavelength and the speed of the reaction front are shown to depend on the value of the initial concentrations of the acid and of the color indicator and on their ratio. A reaction-diffusion model based on charge balances and ion pair mobility explains how the instability scenarios change when the concentration of the reactants are varied.

Graphical abstract: Differential diffusion effects on buoyancy-driven instabilities of acid–base fronts: the case of a color indicator

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Article information

DOI
https://doi.org/10.1039/C1CP21185D
Article type
Paper
Submitted
14 Apr 2011
Accepted
26 Jul 2011
First published
31 Aug 2011

Phys. Chem. Chem. Phys., 2011,13, 17295-17303

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Differential diffusion effects on buoyancy-driven instabilities of acid–base fronts: the case of a color indicator

S. Kuster, L. A. Riolfo, A. Zalts, C. El Hasi, C. Almarcha, P. M. J. Trevelyan, A. De Wit and A. D'Onofrio, Phys. Chem. Chem. Phys., 2011, 13, 17295 DOI: 10.1039/C1CP21185D

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