ORIGINAL RESEARCH article
Front. Phys.
Sec. Interdisciplinary Physics
This article is part of the Research TopicUnraveling Precipitation Patterns: Mechanisms of Geochemical and Geophysical Self-OrganizationView all articles
Spatiotemporal dynamics in a silver thiosulfate, silver sulfide reaction-diffusion system
Provisionally accepted
- Notre Dame University – Louaize, Zouk Mosbeh, Lebanon
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Liesegang pattern formation is a self‐organizing phenomenon governed by diffusion and reaction kinetics generally in a porous matrix. This study investigates the transient precipitation dynamics of silver thiosulfate and its subsequent formation into silver sulfide Liesegang pattern within gelatin matrices through the diffusion of sodium thiosulfate into silver nitrate. The interplay between the decomposition of Ag2S2O3 to Ag2S and its dissolution into soluble [Ag(S₂O₃)₂]³⁻ complex ion under excess thiosulfate produces Ag2S periodic patterned bands. The migration extent of the Ag2S2O3 band increases with increasing concentration gradient and its width increases with increasing gelatin percentage. The Ag2S bands morphology and clarity are primarily regulated by the gelatin structure and solvent polarity, with potassium fluoride, an inert salt contributing to sharper boundaries through increased complex ion and colloid stability. The system successfully isolates the thermodynamically unstable silver thiosulfate, produces in some cases equidistant silver sulfide Liesegang pattern for the 2.5 % gelatin systems, and reveals that pattern morphology and spacing can be tuned by modifying experimental conditions. In addition, this study is significant for understanding a unique class of Liesegang patterns wherein the kinetics of dissolution and dissociation are alternating in response to the diffusion of a counter ion that initially forms a precipitate at the reaction front.
Keywords: self‐organization, reaction‐diffusion kinetics, Liesegang patterns, Silver thiosulfate, Silver sulfide
Received: 25 Jul 2025; Accepted: 02 Dec 2025.
Copyright: © 2025 Badr. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Layla Badr
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