Aluminium chlorohydrate

Aluminium chlorohydrate is a group of salts having the general formula AlnCl(3n-m)(OH)m. It is used in deodorants and antiperspirants and as a flocculant in water purification.

In water purification, where it is usually called polyaluminium chloride, this compound is preferred in some cases because the pH value can be varied according to the exact values chosen for the subscripts n and m in the pattern formula. Although many variations are used, an especially important combination is Al12Cl12(OH)24. The actual pH correlates to the formula m/(3n).

Structure
Aluminium chlorohydrate is best described as an inorganic polymer and as such is difficult to structurally characterise. However, techniques such as Gel permeation chromatography, X-ray crystallography and 27Al-NMR have been used in research by various groups including that of Nazar and Laden to show that the material is based on Al13 units with a Keggin ion structure and that this base unit then undergoes complex transformations to form larger poly-aluminium complexes.

Synthesis
Aluminum Chlorohydrate can be commercially manufactured by reacting aluminum with hydrochloric acid. A number of aluminum-containing raw materials can be used, including aluminum metal, alumina trihydrate, aluminum chloride, aluminum sulfate and combinations of these. The products can contain by-product salts, such as sodium/calcium/magnesium chloride or sulfate.

Uses
The variation most commonly used in deodorants and antiperspirants is Al2Cl(OH)5. There is no scientific evidence supporting widespread rumors that aluminum salts in deodorants can cause Alzheimer's disease or breast cancer. Amongst others, research published in the Journal of the National Cancer Institute found no evidence whatsoever that these compounds increase the risk of breast cancer. However, aluminium is a neurotoxin that alters the function of the blood-brain barrier, and it is one of the few abundant elements that appears to have no beneficial function to living cells.

Synonyms

 * aluminium hydroxychloride
 * aluminium chlorhydroxide
 * aluminium chloride basic
 * polyaluminium chloride (or polyaluminum chloride)