[Archy12345]

2H₂O  O₂ + 2H₂

I need an oxygen rich environment in a flask for an experiment I'm doing.

I'm trying to obtain the oxygen through the standard electrolysis of water. I dissolved some magnesium sulfate in the water I was splitting to conduct the electricity. I have an old 12V AC to DC transformer that I'm using as the electricity source. Both the anode and cathode are copper wire. I did the old technique of filling the collection flask with water and turning it upside down in the water, and I made sure there were no bubbles. (I did this with two collection flasks; one for oxygen and on for hydrogen.)

After turning on the current, I struggled to produce any oxygen at all; practically none. Around the the rims of the hydrogen flask there was this green/blue material that formed. Seemingly insoluble.
I filled up almost half of the hydrogen flask with hydrogen, but the oxygen flask didn't even have an eight of what it should have had.

Anyone know what's going on here? I didn't used distilled water, but I really don't think that was the problem. Could the use of copper for both electrodes have an effect?

Thanks,
Ben

[Arkcon]

I'm uncertain what the problem may be.  Generally, bare copper ware should work, but its possible the oxygen oxidized the copper as fast as it was produced.  Maybe you'd like to try using a mechanical pencil lead as an electrode, maybe by using melted wax or other easily melted insulator to cover all exposed copper.

[Archy12345]

That would explain the lack of oxygen. Thank you very much, I will try the pencil lead idea.

[billnotgatez]

People have used carbon rods from fashioned carbon-zinc batteries
Taking care not to get the electrolyte on their hands etc.

[curiouscat]

I have an old 12V AC to DC transformer that I'm using as the electricity source.

Are  you sure it's a rectifier and not a transformer alone? 

[Archy12345]

I have an old 12V AC to DC transformer that I'm using as the electricity source.

Are  you sure it's a rectifier and not a transformer alone?

Yes, I am. Ha, I had thought about that before as a possible reason for the thing not working.

Come to think of it, I have a couple carbon electrodes I could try.

[curiouscat]

I have an old 12V AC to DC transformer that I'm using as the electricity source.

Are  you sure it's a rectifier and not a transformer alone?

Yes, I am. Ha, I had thought about that before as a possible reason for the thing not working.

How did you check?

[Archy12345]

I have an old 12V AC to DC transformer that I'm using as the electricity source.

Are  you sure it's a rectifier and not a transformer alone?

Yes, I am. Ha, I had thought about that before as a possible reason for the thing not working.

How did you check?

It states on it "Input: AC 120v Output: DC 12v"