Expert: Henry Boyter - 6/21/2004

Question
I'm 46 yo lay person interested in anti perspirant ingrediants. My pharmicists told me that aluminum chloride and aluminum dichlorohydrate are basically the same thing. I got curious and tried to research it online. I could only find that they are both chemicals used in antiperpirants, which I already knew. I tried looking up the definitions on a web site called chemnet.com (I think that was it)as well as trying several other sites. I would get a definition for aluminum chloride but not for aluminum dichlorohydrate. I did find a definition for aluminum chlorhydrate. I'm just a little curious and am in such of a strong over the counter deoderant/antipersirant that is comparible to the presciption, which is 20% aluminum chloride.
Thanks, Thomas

Answer
aluminum chloride   =   AlCl3

aluminum chlorohydrate  =  [Al2(OH)5Cl]x-2H20

aluminum dichlorohydrate  =  [Al2(OH)4Cl2]x-xH20

The later two are polymers of aluminum formed in the presence of water and chlorine.  AlCl3 can be turned into the latter two, but chemcially they aren't the same.  The latter two are sometimes called polyaluminumchloride (PAC.
They have the same function (so basically the same thing) in cosmetic uses, but as to their effectiveness, I'm not an expert.  The -2H20 means two water molecules are trapped in the structure of the solid.  The x just indicates the polymers can have more than one unit.