[lost and found]

I was performing electrolysis on KCl to make KOH. I had two containers connected by a salt bridge. At the time, I didn't have any graphite to use for electrodes, so I just used a bit of aluminum from a beer can. I let the device run overnight. When I checked it this morning, I found a gray podwer at the bottom of the cup containing the positive electrode. The strip of aluminum had disappeared! All that was left was a little bit that hadn't been inside the liquid.

Can anyone explain what happened?

MB

[puppy8800]

Don't you know that the KOH and chlorine will react with aluminium?
That grey powder is probably impurities in "aluminium"

[lost and found]

The two containers were seperated by a salt bridge. Can KOH pass over the bridge?

[AWK]

Both can react

[puppy8800]

Salt bridge used in electrolysis?
could you draw a picture of your device?

[ARGOS++]

Dear Lost and found;


A Stupid Question:  
Which electrode is for you the positive electrode?  Is positive for you the electrode you connected with the positive pole of your power supply? Did you remember that electrons flow opposite to the technical current?

Anyway it seems that you have forgotten, that in one “half-part” of the electrolyse cell you generated “Eau de Javel” that will destroy the oxide passivation of the very reactive aluminium definitely with time. Independent: Chlorides are poison for the oxide passivation.

On the other “half-part” of the electrolyse cell (I suggest you used on both cells aluminium strips!) you may generate your KOH, but just on the surface of the aluminium oxide the concentration will be of such high that the aluminium oxide goes into solution and the “naked” aluminium can not resist anymore and for a long time.

Which of both processes will finally be faster I can’t tell at the moment, maybe the KOH.

But definitely aluminium is one of the worst choices you could take in this situation, independent how you constructed the cells and the bridge.

Good Luck!
                   ARGOS⁺⁺

[lost and found]

puppy8800, here's a picture

ARGOS, I didn't have graphite at the time, so I quickly decided to use aluminum and copper. Yes, the positive electrode is connected to the positive pole of my power supply. Sorry about the confusion.

[ARGOS++]

Dear Lost and found;

Whit your experimental design it should now be clear, that you dissolved the aluminium oxide and the blank aluminium disappeared as it successively re-builds the oxide as long as it was in contact with the KOH of enough concentration you just built, - Sorry!

I hope that in the meantime you found an old empty battery.

Good Luck!
                   ARGOS⁺⁺

[ARGOS++]

Dear Lost and found;

Sorry I forgot:
Yes you are right! – Because you did not immobilise the Ion-Travelling inside the bridge, so also travelling of ions (of all different kinds, not only the “proton”) takes place in the bridge, at least by concentration diffusion, but also driven by the “electrical field”.

Good Luck!
                   ARGOS⁺⁺