pdt@mhuxv.UUCP (12/08/83)
As long as people are asking chemistry-related questions (and relating questionable chemistry), a few facts might make a welcome change. :-) First and certainly least of all, aluminum is trivalent in its garden- variety oxide: its formula is Al(sub 2)O(sub 3), not AlO(sub 2) as suggested. (If it's not worth doing, it's not worth doing right.) Second, as one reader suggested (I'm sorry I forgot your name), aluminum is coated by an oxide which is quite chemically inert. Even concentrated nitric acid will not dissolve aluminum because it cannot attack the oxide. On the other hand, dilute acid with small amounts of what (we) chemists call "complexing agents" (like chloride or citrate, for example) WILL dissolve aluminum: the complexing agent facilitates the dissolution of the oxide because the aluminum complex in solution is more stable than the oxide. Nitrate (as in nitric acid) forms no stable aluminum complexes; so nitric acid can't dissolve the bulk metal because it can't get to it, but acidic solutions containing salt (like spaghetti sauce) can. Another reader (chemists can be forgetful) points out that base (alkaline solutions) dissolves aluminum. Hydroxide attacks BOTH the aluminum oxide and the aluminum metal, releasing a lot of energy. This is what makes Drano (tm), a mixture of sodium or potassium hydroxide and bits of aluminum, heat up drain clogs. Once aluminum hits your tummy, your digestive juices probably turn it into the tetrachloroaluminate(III) ion, [AlCl(sub 4)](sup -1). In order for this species to be metabolized, the reacting biochemical must (1) produce a more stable complex and (2) do so rather quickly. I have no doubt that we have such things in us--I haven't a clue as to what or where they are, though. Once a big globby protein has grabbed on to the aluminum, its outside may still be subtly reactive with other biochemical species (like brain tissue, where it may accumulate). Without knowing the identity of these biochemicals, it's impossible to say whether the aluminum accumulation is a symptom or a cause of Alzheimer's syndrome. Aren't you glad you didn't ask?