Aluminum acetate is a salt derived from the chemical combination of aluminum and acetic acid, widely used in topical medications and industrial processes. The specific chemical formula for the neutral form is \(\text{Al}(\text{C}_2\text{H}_3\text{O}_2)_3\).
Deconstructing the Chemical Formula
The formula \(\text{Al}(\text{C}_2\text{H}_3\text{O}_2)_3\) is determined by the chemical principle of charge neutrality, as aluminum acetate is an ionic compound. It is formed by the electrostatic attraction between the positively charged aluminum ion (\(\text{Al}^{3+}\)) and the negatively charged acetate ion (\(\text{C}_2\text{H}_3\text{O}_2^-\)).
To achieve a neutral charge, the single \(\text{Al}^{3+}\) ion must be paired with three \(\text{C}_2\text{H}_3\text{O}_2^-\) ions. The three negative one charges (\(3 \times -1\)) balance the single positive three charge (\(+3\)). The parentheses in the formula indicate that the subscript “3” applies to the entire acetate group.
The acetate ion is sometimes written using its structural formula as \(\text{CH}_3\text{COO}^-\), resulting in the alternative notation \(\text{Al}(\text{CH}_3\text{COO})_3\). Both notations represent the exact same compound, which is formally named aluminum triacetate. This structure allows the compound to dissociate into its constituent ions when dissolved in water.
Key Physical Properties
Aluminum acetate in its pure, neutral form is a white, crystalline solid. While stable at room temperature, it decomposes when heated to high temperatures, releasing water and acetic acid instead of melting.
A defining property is its high solubility in water, forming a clear, colorless liquid that is slightly acidic due to hydrolysis. The compound is also hygroscopic, meaning the solid form absorbs moisture from the surrounding air.
It can also be found in various hydrated forms, such as aluminum acetate tetrahydrate, where water molecules are incorporated into the crystal structure. Its ability to dissolve readily makes it highly suitable for external medical applications.
Primary Uses in Medicine and Industry
Aluminum acetate is highly valued in medicine and industry primarily because of its powerful astringent properties. An astringent causes the mild coagulation of proteins on the skin’s surface, leading to the constriction of body tissues. This effect helps to dry out weeping or oozing skin conditions and reduce inflammation.
In medicine, aluminum acetate is the active ingredient in over-the-counter topical preparations like Burow’s solution and Domeboro powder packets. These solutions are used as soaks or wet dressings to provide temporary relief for minor skin irritations.
Common conditions treated include:
- Rashes from poison ivy, oak, or sumac
- Insect bites
- Athlete’s foot
- Contact dermatitis
The compound is sometimes incorporated into otic (ear) solutions to help manage chronic ear infections or swimmer’s ear. The most common form used in these preparations is basic aluminum diacetate, known for its mild antiseptic action.
Beyond medicine, aluminum acetate has significant industrial applications, particularly within the textile industry. It functions as a mordant, fixing dyes to fabric by forming a stable complex between the dye molecule and the fiber. Historically, its astringent action was also utilized in some antiperspirant formulations to constrict sweat ducts.