I have a solution of 3500 ml $\ce{H2O}$ + 454 g $\ce{NaHCO3}$ in electrolysis at a potential of 12.5V using a lead anode and copper cathode. The surface areas aren't measured but they are enormous. I made the electrodes myself from lead and copper foil.

The idea was to make NaOH from $\ce{NaHCO3}$ (an inexpensive source $\ce{NaHCO3}$ $$0.86/454g and NaOH $7/500g) meanwhile producing the PbO2 layer on the lead anode.

Everything seemed to be going as expected until I see there's a pale blue species being produced. What could it be? I'm thinking H2O2, water having the potential to completely become peroxide, so I used the 5V output instead and the blue species vanished.

I've read electrolysis of salts in basic solution usually result in the salt reaching its highest state of oxidation at the anode.


$\ce{NaCl + H2O ->Cl- + OH- -> HClO + OH- ->ClO2- + H2}$ eventually becoming $\ce{ClO4-}$

(correct me if I'm wrong but I believe that's the way that reaction carries out),


$\ce{(NH4)2SO4 -> (NH4)2S2O8}$

EDIT It's just copper. Apparently in a solution of NaOH, there is some oxidation of a Cu cathode. I've seen it occur many times afterward. Hydrogen peroxide cannot be made without special laboratory equipment.

  • 2
    $\begingroup$ Wasn't there a copper wire? $\endgroup$ – Mithoron Jan 15 at 0:19
  • $\begingroup$ copper cathode so nope, and remember the blue color comes back when it's reacted with something else. I also reacted it with ammonia with no tetraamine formation. $\endgroup$ – user14828 Jan 15 at 1:21
  • 3
    $\begingroup$ Well, if there was copper then however you did it, it's much more probable then any peroxides or other highly oxidated species (which aren't colorful BTW). $\endgroup$ – Mithoron Jan 15 at 1:56
  • 1
    $\begingroup$ Copper oxidation $\endgroup$ – Alchimista Jan 15 at 10:05

The blue color was caused by copper being stripped from the wire. btw, when your hair turns orange, it is because it is being stripped of color, among other other things (chemical bonds), which will cause it to be brittle and also absorb any hair dye to the extreme that it feels waxy...I'd suggest you cut off a piece of hair for a test before dunking your whole head in bleach (chlorine will turn it greenish).

P.S. Use nitric acid to dissolve Cu.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.