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Related Concept Videos

Electrochemical Systems01:24

Electrochemical Systems

Electrochemical systems provide a fascinating insight into the dynamic interplay of charged species within various phases. One notable example is the interaction between a membrane permeable to K⁺ ions but not to Cl⁻ ions, separating an aqueous KCl solution from pure water. As K⁺ ions diffuse through the membrane, they generate net charges on each phase, leading to a potential difference between them.Similarly, when a piece of Zn is immersed in an aqueous ZnSO₄ solution, the Zn metal, composed...
Surface Active Agents01:27

Surface Active Agents

Surfactants, named for their behavior at interfaces, positively adsorb at the interfaces of two phases, reducing interfacial tension. Their versatility as emulsifiers, detergents, and foaming agents stems from this ability. Surfactants, often termed amphiphiles, share the property of amphipathy, with molecules having both hydrophilic and hydrophobic portions. The hydrophilic part is called the head, and the hydrophobic part, including an elongated alkyl substituent, forms the tail.Surfactants...
Micelles01:30

Micelles

Micelle formation is an intricate process that hinges on the properties of amphiphilic or amphipathic molecules and the conditions of the system in which they are found. Amphiphilic molecules, which have both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts, play a critical role in this process.In aqueous environments, these molecules arrange themselves such that their hydrophilic heads are turned towards the water phase, while their hydrophobic tails are oriented away...
Ionic Strength: Effects on Chemical Equilibria01:19

Ionic Strength: Effects on Chemical Equilibria

The addition of an inert ionic compound increases the solubility of a sparingly soluble salt. For example, adding potassium nitrate to a saturated solution of calcium sulfate significantly enhances the solubility of calcium sulfate. Le Châtelier's principle cannot predict this shift in the equilibrium. Instead, this could be explained in terms of changes in the effective concentration of the ions in solution in the presence of added inert salt.
In this solution, the primary cation—the calcium...
Ion Exchange01:17

Ion Exchange

Ion exchange chromatography separates charged molecules from a solution by reversibly exchanging them with mobile, or 'active', ions associated with the oppositely charged stationary phase. This method can be used to separate ions, soften and deionize water, and purify solutions. The polymers comprising the ion-exchange column are high-molecular-weight and chemically stable polymers, crosslinked to be porous and essentially insoluble. They are also functionalized with either acidic or basic...
Factors Affecting Solubility04:01

Factors Affecting Solubility

Compared with pure water, the solubility of an ionic compound is less in aqueous solutions containing a common ion (one also produced by dissolution of the ionic compound). This is an example of a phenomenon known as the common ion effect, which is a consequence of the law of mass action that may be explained using Le Chȃtelier’s principle. Consider the dissolution of silver iodide:

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Phase Behavior of Charged Vesicles Under Symmetric and Asymmetric Solution Conditions Monitored with Fluorescence Microscopy
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Phase Behavior of Charged Vesicles Under Symmetric and Asymmetric Solution Conditions Monitored with Fluorescence Microscopy

Published on: October 24, 2017

Salt-induced phase inversion in aqueous cationic/anionic surfactant two-phase systems.

Yan-Qing Nan1, Li-Sheng Hao

  • 1Department of Chemistry, Hunan Normal University, Changsha, People's Republic of China. nanyq@21cn.com

The Journal of Physical Chemistry. B
|September 5, 2008
PubMed
Summary
This summary is machine-generated.

Phase inversion in aqueous two-phase systems (ATPS-C) occurs when specific salts like NaF or NaCl are added, altering ion concentrations and phase densities. This phenomenon is crucial for understanding surfactant behavior in these systems.

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Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets
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Area of Science:

  • Physical Chemistry
  • Surfactant Science
  • Colloid Science

Background:

  • Aqueous two-phase systems (ATPS) are widely used in separation processes.
  • Cationic surfactant-based ATPS (ATPS-C) exhibit unique phase inversion behaviors.
  • Understanding phase inversion is key to optimizing ATPS applications.

Purpose of the Study:

  • To investigate the phase inversion of ATPS-C formed by 1,3-propanediyl bis(dodecyl dimethylammonium bromide) (12-3-12) and sodium dodecyl sulfonate (AS).
  • To determine the effect of various inorganic salts on phase inversion.
  • To elucidate the mechanisms driving phase inversion in these systems.

Main Methods:

  • Preparation and manipulation of ATPS-C at 318.15 K.
  • Addition of inorganic salts (NaF, NaCl, NaHCO3, NaNO3, NaBr) to induce phase inversion.
  • Transmission Electron Microscopy (TEM) for microstructure analysis.
  • Phase composition, density, and volume ratio measurements.
  • Analysis of counterion exchange and Hofmeister series effects.

Main Results:

  • Addition of NaF, NaCl, NaHCO3, or NaNO3 induced phase inversion in 12-3-12/AS ATPS-C, while NaBr did not.
  • TEM revealed no direct correlation between concentrated phase microstructure and phase inversion.
  • Phase composition analysis showed exchange of bromide counterions with added anions.
  • Density changes in the dilute and concentrated phases were critical, with the dilute phase density increasing more significantly.
  • The density contribution of added anions and their Hofmeister series order influenced phase inversion.

Conclusions:

  • Phase inversion in ATPS-C is driven by counterion exchange and differential density changes between phases upon salt addition.
  • The nature of the added inorganic anion (density contribution and Hofmeister effect) dictates its ability to induce phase inversion.
  • Microstructure alone does not determine phase inversion; thermodynamic factors like density and ion interactions are paramount.