Title: Spatial Heterogeneity and Imperfect Mixing in Chemical Reactions: Visualization of Density-Driven Pattern Formation

Abstract

Imperfect mixing is a concern in industrial processes, everyday processes (mixing paint, bread machines), and in understanding salt water-fresh water mixing in ecosystems. The effects of imperfect mixing become evident in the unstirred ferroin-catalyzed Belousov-Zhabotinsky reaction, the prototype for chemical pattern formation. Over time, waves of oxidation (high ferriin concentration, blue) propagate into a background of low ferriin concentration (red); their structure reflects in part the history of mixing in the reaction vessel. However, it may be difficult to separate mixing effects from reaction effects. We describe a simpler model system for visualizing density-driven pattern formation in an essentially unmixed chemical system: the reaction of pale yellow ${\text{Fe}}^{\text{3}+}$ with colorless ${\text{SCN}}^{-}$ to form the blood-red Fe ${\left(\text{SCN}\right)}^{2+}$ complex ion in aqueous solution. Careful addition of one drop of Fe $\left({\text{NO}}_3\right)3$ to KSCN yields striped patterns after several minutes. The patterns appear reminiscent of Rayleigh-Taylor instabilities and convection rolls, arguing that pattern formation is caused by density-driven mixing.

Authors:

Sobel, Sabrina G. ^[1]; Hastings, Harold M. ^[2]; Testa, Matthew ^[2]

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+ Show Author Affiliations

1. Department of Chemistry, Hofstra University, Hempstead, NY 11549-1510, USA
2. Department of Physics and Astronomy, Hofstra University, Hempstead, NY 11549-1510, USA

Publication Date:

Wed May 06 00:00:00 EDT 2009

Sponsoring Org.:

USDOE

OSTI Identifier:

1198248

Grant/Contract Number:  

FG02-08ER64623

Resource Type:

Published Article

Journal Name:

Research Letters in Physical Chemistry

Additional Journal Information:

Journal Name: Research Letters in Physical Chemistry Journal Volume: 2009; Journal ID: ISSN 1687-6873

Publisher:

Hindawi Publishing Corporation

Country of Publication:

Country unknown/Code not available

Language:

English