Ask A Scientist Chemistry Archive

Question:
Just a quick question.  I am making thermite and need powdered Al.
First I dissolved aluminum foil in HCl to make AlCl3. Next I tried to
find magnesium to precipitate out the Al but I can't get any.
 
If I electrolyze the aqueous AlCl3 will the Cl be driven off as a gas?
I would rather not try it until I know it works.
 
Jon Sauer (Wooly Rupert)
 
Answer:
The Cl- probably will be oxidized and bubble off the anode if you
electrolyze the solution, but the best aluminum you'll get is a coating
on the cathode.  It's not like Al powder will start falling out of the 
solution.  Your best bet for Al powder is to order some from Aldrich
or someplace and use that.  The stuff you get from electrolysis won't
be nearly fine enough to use in a thermite reaction (nor plentiful
enough!).  I speak from experience here...I tried to use, I think, 30
mesh Al and it wasn't enough to get the reaction going.  It was impossible
trying to grind it smaller too.  Good luck.
-Joe Schultz