Why did my electrodes react this way when passing current through ascorbic acid?

[Justonium]

I was using two steel electrodes to pass a current through a solution of ascorbic acid. The negative electrode was the only one that bubbled at first (hydrogen bubbles of course). But when I came back an hour later I was most surprised to find both electrodes bubbling, and many different things going on. Both electrodes were bubbling, and the negative electrode was actually corroded! It had turned dark black. There were also pieces of this black substance falling off, which aligned when put under a magnetic field. The positive electrode had corroded too, but was a lighter, grayish color. In addition to this, a soluble violet salt was dissolving off of it. When the electricity was turned off, the grayish surface did not dissolve, indicating that two different salts had formed on its surface. Both electrodes remained bubbling for quite a while, though the next morning when I took them out, they both looked no different than they had before, the negative one black, and the positive one gray. Three different substances were formed in this multi-variabled experiment, one of which which was actually on the negative electrode. Could anybody give any insight as to what the heck has happened?

[Theophrastus]

While I am unable to pinpoint an exact compound, I would guess that your violet salt was probably a mixture of various isomers of iron complexes, such as the following complex (hypothetically speaking):

 

[ce] Fe(HO-CH-CO-CH-CH2(OH)-CH2-OH)2 [/ce]

 

(In this case, the CH's are positively charged, and bonded to the central iron atom)

 

The gas released by the cathode was probably carbon dioxide (look up Kolbe Electolytic Synthesis) and of course, hydrogen gas, was released at the anode. Other than that, your remaining compounds are quite the mystery to me. While the black anodic precipitate sounds like magnetite to me ([ce] Fe3O4 [/ce]); how the iron got that way however, I have no idea. I would think that given oxygen gas, you would attain iron carbonate as a precipitate from the cathode, but again, electrolysis is a confusing process, with mixed results. I would keep some of the products though for analysis. In this respect, I'm sorry if my post was too late. If you still have the products, it might be interesting to do some ion tests on the precipitates. (If the yield was sufficient, saving some, if identified, for later use.)

Cheer!

 

-Theo

 

ps: I'll get some steel nails, and some ascorbic acid from my local pharmacy and try the process out for myself. Can you give me some precise details on your execution? (voltage, current, temperature, electrolyte concentration, temperature, etc.) In doing so, I'm wondering if I can (a) destabilize my theorized complex with conceptrated acid, and then perform some cool ion tests, and other testing as to the nature of the ligands.

Edited September 26, 2009 by Theophrastus

[alex folen]

Yes, would do the same, making sure ALL variables are in front of me to the best of our knowledge. Gosh, I must have nothing to do now.