# Pale blue species forming during electrolysis of NaHCO3

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.

Eg.:

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

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

or

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

EDIT

I believe I've synthesized $$\ce{MgS2O8}$$ (peroxydisulfate) in the same manner, which apparently oxidizes copper (I shut it off n fell asleep, it consumed its cathode, lol) and does absolutely nothing to $$\ce{Mg(OH)2}$$. Which I had to try because I wanted to be sure I could put sulfur in its highest state of oxidation like I've read was possible. I'm pretty sure I synthesized the desired product because even $$\ce{H2SO4}$$ can't oxidize Cu unless it's hot, but peroxydisulfates do oxidize copper (I have a new PC board etchant!!) and bleach hair (I've always wanted to bleach my hair orange):

$$\ce{MgSO4 + H2O -> SO4- +OH- ->HSO5- +OH- -> MgS2O8 + H2O + Mg(OH)2 }$$

Oh and :

$$\ce{MgS2O8 + Cu -> CuSO4 + MgSO4}$$

Making the acid from the salt should be a lot of fun. However, I am obviously no chemist, I'm an ε = Νδφ/δτ kind of guy so..

What could the blue species have been?

What could I be making instead of NaOH? Am I even Making NaOH?

• Wasn't there a copper wire? – Mithoron Jan 15 at 0:19
• 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. – user14828 Jan 15 at 1:21
• 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). – Mithoron Jan 15 at 1:56
• Copper oxidation – Alchimista Jan 15 at 10:05