Ammonium alum
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Ammonium alum (NH4Al(SO4)2·12H2O) or ammonium aluminium sulfate dodecahydrate is a white crystalline double sulfate of aluminium, used in water purification, in vegetable glues, in porcelain cements, in natural deodorants and in tanning, dyeing and in fireproofing textiles.[1]
The pH of the solution resulting from the topical application of ammonium alum with perspiration is typically in the slightly acid range, from 4 to 5.[2] It is a popular deodorant because of its high availability and low cost[citation needed]. A 120 gram stone lasts for at least a year of daily usage - much longer than other deodorants and antiperspirants. It is also hypoallergenic and non-staining[citation needed]. Potassium alum is also used for this purpose.
