[billnotgatez]

Check out the sources used by people who make soap as a hobby.

[Mark Imisides]

No idea about the foam. My first idea is contaminants/surfactants.

It's CO2 caused by the reaction of localised hydronium ions (caused by the reaction of ferric ions with water)  at the anode with the bicarb.

Are you trying to tell us that evolving CO₂ makes foam, but evolving hydrogen and oxygen don't?

Correct. The reason is that the former is a homogenous reaction whereas the latter is a heterogenous reaction.

One of the many points about electrolysis that most people on this thread don't appreciate is that the formation of gases at a solid electrode from an aqueous reactant is a hideously slow and inefficient process. The overvoltage for the these processes is huge. For a typical electrolysis reaction the potential difference between the E0 and the potential at which electrolysis occurs is of the order of 300-500 mV. For hydrogen evolution, dependent on the substrate that is used, it is of the order of 700-800 mV.

In the early days of electrolysis, this was referred to as a "bubble overvoltage", and interpreted in terms of the work required to form the bubbles. In recent itmes, however, it is explained in terms of interfacial reaction kinetics, specifically the rate at which electrons transfer across the heterogenous interface. Thus, overvoltage is related to the equilibrium current exchange density.

Bottom line is this - formation of bubbles at electrode interfaces is such a slow process, and influenced by so many variables, that calculations of reaction rates (or Faraday's law) are extremely complex.

The reaction between the H+(aq) and bicarb ions, on the other hand, is an extremely fast process that produces a great deal of effervescence. One of the qualitative tests for carbonate or bicarbonate ions, as I'm sure you're aware, is the addition of a small amount of acid - instantaneous effervescence being the result.

[Mark Imisides]

One other thing - the bubbles formed by a heterogenous process are big - they don't dislodge from the electrode surface until their buoyancy overcomes their adsorptive attraction to the electrode which, depending on the surface energy of the electrode, can be quite large. The outcome of this is that bubbles formed at an electrode surface are usually large enough to actually see.

Bubbles formed by a homogenous reaction on the other hand, are so small that all you see is the foam that they produce (the result of the massive surface area of the air/liquid interface)

[Borek]

Sorry, but your explanation to the foam creation doesn't make sense to me. First of all, OP told us:

Using sodium bicarb as a catalysis...the water over time deveopes a thick layer of white foam that floats on top of the water.

Over time, so it is building up, it is not a thing present all the time, it is not a thing that appears at the very beginning. It is not kind of a short lasting foam you are probably referring to (at least that's what I can guess form your description).

Second, amount of bicarbonate in the solution is limited, so (assuming it is a simple acid base reaction) it will be a problem only at the very beginning. Again, from the description it is not.

Third, overvoltage has to be taken into account when designing cell and calculating its parameters, no doubts about it, but we are talking about using voltages that should be easily able to overcome the problem. That means that the main limiting factor is the solution resistance which limits current we can use.

Finally, you suggest that H⁺ is produced by the reaction of Fe³⁺ with water:

It's CO2 caused by the reaction of localised hydronium ions (caused by the reaction of ferric ions with water)  at the anode with the bicarb.

While it is very likely that electrode corrodes, it is not a fast process, so amount of H⁺ produced will be low, for sure not high enough to make bicarbonate react as fast as you seem to suggest. We have several processes taking place, let's concentrate on two of them. On the anode dissolution of iron, followed by the carbon dioxide evolution:

Fe -> Fe³⁺ + 3e^- (not necesarilly one step, but it doesn't matter for our calculations)
Fe³⁺ + 3H₂O -> Fe(OH)₃ + 3H⁺ (probably much more complicated, as there are many complexes involved)
3H⁺ + 3HCO₃^- -> 3H₂O + 3CO₂

bottom line is - 1 electron used for corrosion, one molecule of carbon dioxide.

On the cathode:

2H⁺ + 2e^- -> H₂

2 electrons, one molecule of evolving gas.

Even assuming that there are no other reactions but iron dissolution occuring on the anode, amount of carbon dioxide evolving will be only twice larger than the amount of hydrogen evolving. This is not as huge difference in speed as you suggest, and that's only assuming there is no oxygen evolving at the anode at all. There is oxygen evolving and anode corrosion is a slow process, so amount of carbon dioxide evelving should be much, much lower.

[billnotgatez]

Mark Imisides New Member -- Do you have examples of gas or liquid electrodes that are currently being used for this process?

[nj_bartel]

Ill look into the carbon.

Sodium hydroxide is caustic soda or lye...a little dangerous. But "The Works" toilet bowl cleaner is 20% NaOH so ill mix some in and hope for the best. The extra 80% is the problem. They might be bad contaminates.

KOH is another form of lye....I dont know where to get it as easily as the NaOH

No no no.  'The Works' is Muriatic Acid, 20% by weight HCl in aqueous solution - no contaminants.  Just a heads up.

And I believe KOH is in stump remover, not positive though.

[Borek]

Some types of drain cleaners are NaOH based. Either H₂SO₄ or NaOH in these things, both can be used as an electrolyte in water electrolysis.

[billnotgatez]

I have never made soap from scratch except in a class laboratory.
But, there are many hobbits that do make soap.
I Googled "soap making sodium hydroxide" and selected this site.


Potassium hydroxide is known as caustic potash
Sodium hydroxide is known as caustic soda


http://www.thesoapdish.com/caustics.htm

[aarothepharo]

i wonder is a hobby or craft store carries NaOH.

[nj_bartel]

possibly, but NaOH = oven cleaner.

[billnotgatez]

nj_bartel

how pure or is that even important

[aarothepharo]

TO EVERYONE READING THIS POST...Im going to switch to carbon rods for electrodes so we dont have to worry about IronOxide. Is carbon rods ok with everybody?

If you are still actively participating in this thread please post a list, in your opinion, of electrolyts that you think may be a good choice. I will pick the most popular answer and try it.

Ill run the expirement again when I get the Carbon rods. Unless anyone has an objection to the carbon.

Please everybody submit a list.

[nj_bartel]

nj_bartel

how pure or is that even important

Pretty sure some of them come as pure as you can make it, while others come with scouring agents.

[billnotgatez]

This guy used carbon rods
See how he got them from old batteries

http://sci-toys.com/scitoys/scitoys/echem/echem.html

I take it you did not search this forum or the web as I suggested

[mir]

When I was young, I used graphite rods from two dynamos as electrodes for electrolysis of salt water. But for some reason the graphite rods dissolved. Huh, how curious is that?

I also tried tin and even nails. But they made stinking soup of something.