Related Experiment Video
Updated: Jul 19, 2026
08:50
The Mechanics of (Poro-)Elastic Contractile Actomyosin Networks As a Model System of the Cell Cytoskeleton
Published on: March 10, 2023
Some non-equilibrium phenomena in the malic acid/water/Polysorbate 81 system
Abeer Al Bawab1, Stig E Friberg, Mateus M Bergamaschi
1Chemistry Department, Faculty of Science, University of Jordan, P.O. Box 13536, Amman 11942, Jordan.
International Journal of Pharmaceutics
|October 31, 2006
Summary
Topical hydroxy acid formulations applied to skin do not reach equilibrium, contrary to common assumptions. Their structural changes are slow and non-equilibrium, impacting cosmetic and dermatological treatments.
Area of Science:
- Cosmetic Science
- Dermatology
- Physical Chemistry
Background:
- Topical formulations change structure upon skin application.
- These structural changes are often assumed to reach equilibrium.
- Hydroxy acids are common in cosmetic and dermatological treatments.
Purpose of the Study:
- Investigate non-equilibrium conditions in hydroxy acid systems.
- Determine if topical formulations reach equilibrium after application.
- Analyze the kinetics of structural changes in hydroxy acid systems.
Main Methods:
- Brought different, non-equilibrium phases of hydroxy acid systems into contact.
- Avoided convection to isolate phase transfer.
- Estimated substance transfer by measuring volume changes in each phase.
Main Results:
- Hydroxy acid systems remained far from equilibrium even after prolonged contact.
- Kinetics of change varied significantly: extremely slow for solid phases, fast for liquid phases.
- A novel separated layer was observed, not present in equilibrium phase diagrams.
Conclusions:
- Topical hydroxy acid formulations exist under non-equilibrium conditions.
- The structural dynamics are complex and time-dependent, not reaching equilibrium.
- These findings have significant implications for cosmetic and dermatological applications of hydroxy acids.
Related Concept Videos
03:24Common Ion Effect
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 Châtelier’s principle. Consider the dissolution of silver iodide:
01:19Composition of Polyprotic Acid Solutions as a Function of pH
Polyprotic acids of the type H2M constitute two ionizable protons. As a result, on titration with a base, they exhibit two equivalence points in the titration curve. During titration, the species H2M, HM−, and M2− will be present in the solution at different points. The fractions of H2M, HM−, and M2− present at the various instances of the titration are denoted by α0, α1, and α2, respectively.
A graph with the alpha values is plotted against the volume of base added during titration. Here, a...
A graph with the alpha values is plotted against the volume of base added during titration. Here, a...
01:18Titration of Polyprotic Base with a Strong Acid
The titration of a polyprotic base such as sodium carbonate with a strong acid such as hydrochloric acid results in two equivalence points on the titration curve. At the first equivalence point, the carbonate ions in the base are completely converted to bicarbonate ions. The second equivalence point corresponds to the complete conversion of bicarbonate ions to carbonic acid, which dissociates into carbon dioxide and water. The region before the first equivalence point corresponds to the...
04:02Weak Acid Solutions
Few compounds act as strong acids. A far greater number of compounds behave as weak acids and only partially react with water, leaving a large majority of dissolved molecules in their original form and generating a relatively small amount of hydronium ions. Weak acids are commonly encountered in nature, being the substances partly responsible for the tangy taste of citrus fruits, the stinging sensation of insect bites, and the unpleasant smells associated with body odor. A familiar example of a...
01:14Alkylation of β-Diester Enolates: Malonic Ester Synthesis
Malonic ester synthesis is a method to obtain α substituted carboxylic acids from ꞵ-diesters such as diethyl malonate and alkyl halides.
02:45Acid-Catalyzed Hydration of Alkenes
Alkenes react with water in the presence of an acid to form an alcohol. In the absence of acid, hydration of alkenes does not occur at a significant rate, and the acid is not consumed in the reaction. Therefore, alkene hydration is an acid-catalyzed reaction.