# Aluminum powder from aluminum sulfate?

I recently did the experiment where you drop a piece of iron in an aqueous solution of copper sulfate. After a while, the piece of iron gets coated with a fluffy coating of copper that can be dried and mashed into a powder. Apparently this happens because iron is more reactive than copper, according to the reactivity series.

Can I do the same thing by making an aqueous solution of aluminum sulfate, then dropping a piece of magnesium metal in? It should work because magnesium is above aluminum on the reactivity series, right?

• No, you can't. $\,$ – Ivan Neretin Sep 16 at 6:22

The only way of showing that aluminum reacts with water is to dip the aluminum piece in a solution of Mercury chloride. There will be a surface reaction like $$\ce{2 Al + 3 HgCl2 -> 3 Hg + 2 AlCl3}$$ Then the mercury Hg will make an alloy with aluminum. And this alloy cannot be covered by the alumina shield. So such a piece of amalgamated aluminum will be quickly oxidized in air, and will produce long white filaments of $$\ce{Al2O3}$$ or $$\ce{Al(OH)3}$$ if abandoned in air for a couple of minutes due to one of the following reactions $$\ce{4Al + 3 O2 -> 2 Al2O3}$$ $$\ce{4 Al + 3 O2 + 6 H2O -> 4 Al(OH)3}$$ This production of alumina filaments is very interessant to observe. Of course it is not allowed any more today, because of the toxicity of mercury.