Aluminium chlorohydrate

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

In water purification, this compound is preferred in some cases because of its high charge, which makes it more effective at destabilizing and removing suspended materials than other aluminium salts such as aluminium sulfate, aluminium chloride and various forms of polyaluminium chloride and polyaluminium chlorisulfate, in which the aluminium structure results in a lower net charge than aluminium chlorohydrate. Further, the high degree of neutralization of the HCl results in minimal impact on treated water pH when compared to other aluminium and iron salts.

Uses

Aluminium chlorohydrate is one of the most common active ingredients in commercial antiperspirants.^[1] The variation most commonly used in deodorants and antiperspirants is Al₂Cl(OH)₅.

Aluminium chlorohydrate is also used as a coagulant in water and waste water treatment processes to remove dissolved organic matter and colloidal particles present in suspension.

Safety

The Food and Drug Administration considers the use of aluminium chlorohydrate in antiperspirants to be safe and it is permitted in concentrations up to 25%.^[2]

Alzheimer's disease

Studies have found only a negligible association between exposure to and long-term use of antiperspirants and Alzheimer's disease.^[3] There is no adequate evidence that exposure to aluminium in antiperspirants leads to progressive dementia and Alzheimer's disease.^[4]

Heather M. Snyder, the senior associate director of medical and scientific relations for the Alzheimer's Association, has stated, "There was a lot of research that looked at the link between Alzheimer's and aluminium, and there hasn't been any definitive evidence to suggest there is a link".^[5]

Breast cancer

The International Journal of Fertility and Women's Medicine found no evidence that certain chemicals used in underarm cosmetics increase the risk of breast cancer.^[6] Ted S. Gansler, the director of medical content for the American Cancer Society, stated "There is no convincing evidence that antiperspirant or deodorant use increases cancer risk".^[5]

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^[7] and Laden^[8] 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

Aluminium chlorohydrate can be commercially manufactured by reacting aluminium with hydrochloric acid. A number of aluminium-containing raw materials can be used, including aluminium metal, alumina trihydrate, aluminium chloride, aluminium sulfate and combinations of these. The products can contain by-product salts, such as sodium/calcium/magnesium chloride or sulfate.^[9]

Because of the explosion hazard related to hydrogen produced by the reaction of aluminium metal with hydrochloric acid, the most common industrial practice is to prepare a solution of aluminium chlorohydrate (ACH) by reacting aluminium hydroxide with hydrochloric acid. The ACH product is reacted with aluminium ingots at 100 °C using steam in an open mixing tank. The Al to ACH ratio and the time of reaction allowed determines the polymer form of the PAC n to m ratio.

See also

• Aluminium chloride
• Aluminium hydroxide
• Deodorant
• Keggin structure

References

1. Lukacs VA, Korting HC (1989). "[Antiperspirants and deodorants—ingredients and evaluation]". Dermatosen in Beruf Und Umwelt (in German). 37 (2): 53–7. PMID 2656175.
2. Code of Federal Regulations Title 21 21 C.F.R. 350.10
3. Graves AB, White E, Koepsell TD, Reifler BV, van Belle G, Larson EB (1990). "The association between aluminium-containing products and Alzheimer's disease". Journal of Clinical Epidemiology. 43 (1): 35–44. doi:10.1016/0895-4356(90)90053-R. PMID 2319278.
4. Exley C (March 1998). "Does antiperspirant use increase the risk of aluminium-related disease, including Alzheimer's disease?". Molecular Medicine Today. 4 (3): 107–9. doi:10.1016/S1357-4310(98)01209-X. PMID 9575492.
5. "Antiperspirant Safety: Should You Sweat It?". WebMD.
6. Gikas, PD; Mansfield, L; Mokbel, K (2004). "Do underarm cosmetics cause breast cancer?". Int. J. Fertil. Womens Med. 49 (5): 212–4. PMID 15633477.
7. Rowsell J, Nazar LF (2000). "Speciation and Thermal Transformation in Alumina Sols: Structures of the Polyhydroxyoxoaluminum Cluster [Al₃₀O₈(OH)₅₆(H₂O)₂₆]¹⁸⁺ and Its δ-Keggin Moieté". Journal of the American Chemical Society. 122 (15): 3777–8. doi:10.1021/ja993711.
8. Laden, Karl; Felger, Carl B. (1988). Antiperspirants and deodorants. New York: M. Dekker. ISBN 978-0-8247-7893-4.
9. American National Standards Institute (1993). AWWA standard for liquid poly aluminium chloride. Denver: American Water Works Association. OCLC 31849037.