Related Experiment Video
Updated: Jun 14, 2026
13:27
Exploring the Effects of Atmospheric Forcings on Evaporation: Experimental Integration of the Atmospheric Boundary Layer and Shallow Subsurface
Published on: June 8, 2015
Coarsening of precipitation patterns in a moving reaction-diffusion front
1Department of Physics, University of Technology and Economics, 1521 Budapest, Hungary.
Summary
Precipitation patterns in a moving reaction front were studied. The observed self-similar coarsening of aluminum hydroxide precipitate follows a square-root time dependence, matching theoretical models.
Area of Science:
- Physical Chemistry
- Materials Science
- Chemical Engineering
Background:
- Precipitation reactions at moving fronts are complex phenomena.
- Understanding pattern formation is crucial for controlling chemical processes.
- The interplay between precipitation and dissolution influences pattern evolution.
Purpose of the Study:
- To investigate precipitation patterns in a 2D moving front.
- To analyze the time evolution and scaling of aluminum hydroxide precipitate.
- To compare experimental observations with theoretical models.
Main Methods:
- Studied sodium hydroxide (NaOH) diffusion into an aluminum chloride (AlCl3) gel.
- Observed the time evolution of aluminum hydroxide (Al(OH)3) precipitate.
- Analyzed the self-similar coarsening of precipitate patterns.
Main Results:
- Precipitate Al(OH)3 exists in a narrow, optically accessible region due to redissolution.
- Observed self-similar coarsening of precipitation patterns.
- Characteristic length scale (xi) increases with time as xi(t) ~ sqrt(t).
Conclusions:
- Experimental results align with a theory based on Cahn-Hilliard phase-separation dynamics.
- The model accurately incorporates redissolution effects.
- This study provides insights into pattern formation in reactive diffusion systems.
Related Concept Videos
01:12Precipitation Processes
The experimental conditions in a gravimetric analysis should be optimized to maximize the particle size and purity of the obtained precipitate. Ideally, the concentration of the precipitating reagent should be low with effective stirring to maintain low relative supersaturation for the growth of large crystals. In homogeneous precipitation, the precipitant is slowly generated by a chemical reaction in the solution to avoid local reagent excesses. For example, urea decomposes gradually to...
03:10Precipitation Reactions
In a precipitation reaction, aqueous solutions of soluble salts react to give an insoluble ionic compound – the precipitate. The reaction occurs when oppositely charged ions in solution overcome their attraction for water and bind to each other, forming a precipitate that separates out from the solution. Since such reactions involve the exchange of ions between ionic compounds in aqueous solution, they are also referred to as double displacement, double replacement, exchange reactions, or...
01:10Types of Coprecipitation
Coprecipitation is the contamination of a precipitate by otherwise soluble species and occurs via different processes. In colloidal precipitates, coprecipitation occurs via surface adsorption. For instance, barium sulfate has a primary layer of adsorbed barium ions and a secondary layer of nitrate counterions. This results in contamination of the precipitate by barium nitrate.
Sometimes, ions in a crystal lattice can undergo isomorphous replacement by inclusions of similar charge and size. For...
Sometimes, ions in a crystal lattice can undergo isomorphous replacement by inclusions of similar charge and size. For...
01:17Precipitation and Co-precipitation
Precipitation and coprecipitation methods can be used to separate a mixture of ions in a solution. In qualitative inorganic analysis, ions that form sparingly soluble precipitates with the same reagent are separated based on the differences in solubility products. For example, consider the separation of Cu(II) and Fe(II) ions by precipitation as insoluble sulfides. First, copper(II) sulfide is precipitated by the addition of acidic H2S, where the dissociation of H2S is suppressed. Adding H2S...
01:16Precipitate Formation and Particle Size Control
In precipitation gravimetry, the precipitating agent should react specifically or selectively with the analyte. While a specific reagent reacts with the analyte alone, a selective reagent can react with a limited number of chemical species.
The obtained precipitate should be either a pure substance of known composition or easily converted to one by a simple process, such as ignition or drying. In addition, the precipitate should be insoluble and easily filterable. In general, filterability...
The obtained precipitate should be either a pure substance of known composition or easily converted to one by a simple process, such as ignition or drying. In addition, the precipitate should be insoluble and easily filterable. In general, filterability...
03:11Precipitation of Ions
Predicting Precipitation
The equation that describes the equilibrium between solid calcium carbonate and its solvated ions is:
The equation that describes the equilibrium between solid calcium carbonate and its solvated ions is: