Sciencemadness Discussion Board

Unexpected Product From Electrolytic Cell

cpman - 3-10-2014 at 13:12

Hello everyone!
So, today I ran an electrolytic cell with a baking soda electrolyte, a copper anode, and a graphite cathode to make basic copper carbonate.
I ran the cell at 12V DC from a power supply. My multimeter is broken, so I don't know the current.
Lots of bubbles were evolving from both electrodes, as would be expected. The bubbles from the cathode appeared to be H2, and I presume that the anode bubbles were a mix of CO2 and O2. The anode was quickly covered by a greenish-blue solid, and the solid filled the solution. I presume that this is basic copper carbonate, like I expected.
I filtered the solution, and was VERY suprised to see that the filtrate was a light, sky blue color, like a dilute solution of CuSO4.
I'm not sure what this could be.
Is it some sort of complex with carbonate?
Here is a picture of the filtrate next to the percipitate:

Any ideas as to what this solution has aside from NaHCO3 and distilled water?
(Sorry for the big photo...)

Metacelsus - 3-10-2014 at 13:16

I would guess it's a suspension of basic copper carbonate that was small enough to pass through your filter. You could shine a beam of strong light through to test it by seeing if it scatters.

cpman - 3-10-2014 at 15:55

You are right. Thanks a lot.

khlor - 9-10-2014 at 15:34

I done this sort of experiment some time ago, I was using regular table salt (NaCl for the record) and copper electrodes, in the anode I got a dark redish color(Cu2O) and in the solution I got CuOH suspensil, I dried and I got CuO. I think this also happened on yours, but the reaction continued with the CO2 or the carbonate anios.