[CliffordK]

I will also mention that electricity has a wonderful ability to find the path of least resistance, be that the metal your are welding connected to your grounding cable, or through your body.

I find it amazing that a person can generally hold a piece of filler wire in the arc with one's bare hands and not get shocked.  But, your work is generally well grounded, so it is the path of least resistance.  You, on the other hand generally you are not well grounded.  Even touching the grounded work, your body still isn't the path of least resistance.

When you weld your filler wire to the tungsten electrode, away from the work, then I presume most good welders would drop the power output, and you still may not be grounded. 

The problem may occur with one piece of metal that is well grounded, and one that is not, and you in the middle.  Or, the use of a grounded welding table instead of grounding your work, coupled with variable output from your power supply.

Anyway, at this point, we need to get back onto the original topic of carbon electrodes NaOH.

[Lab Rat]

I know what the electrolysis will produce, but I'm doing it outside and wearing a gas mask so I should be alright. Thank you for your concern though.

Do you really need salt in the electrolysis reaction?  If not sodium bicarbonate (baking soda), I don't think, will produce any harmful gases.  However, I am not sure that this will produce sodium hydroxide.  If you have access to it, you can put some elemental sodium in water and this will produce sodium hydroxide.  Be careful, though, as this is quite an explosive reaction-even a small piece of sodium will produce a powerful explosion-small pieces of glowing material may be shot into the air.

[damocles]

I know what the electrolysis will produce, but I'm doing it outside and wearing a gas mask so I should be alright. Thank you for your concern though.

Do you really need salt as your catalyst in the electrolysis reaction?  If not sodium bicarbonate (baking soda), I don't think, will produce any harmful gases.  However, I not sure that this will produce sodium hydroxide however.  If you have access to it, you put some elemental sodium in water and this will produce sodium hydroxide.  Be careful, though, as this is quite an explosive reaction-even a small piece of sodium will produce an explosive reaction; small pieces of glowing material may be shot into the air.

(1) Lab Rat elemental sodium is much more dangerous and much less accessible than caustic soda, which can be readily bought at appropriate stores (hardware stores in this country; do not know what British/North American equivalents are). If the aim is simply to get hold of some caustic soda, there is no need for electrolysis or any other awkward and dangerous chemical procedure, and certainly not to use an extremely dangerous material like metallic sodium. In my student days there was a man at my university who had permanent lifetime employment as a "cleaner" because he had been blinded and had bad facial scars from an accident where water had come in contact with NaK eutectic that was being used as a coolant in some particle physics equipment.

(2) Salt is not a catalyst in this electrolysis reaction, it is a reactant, along with water. The stoichiometric form of the electrolysis reaction is

NaCl + H₂O (+ electrical energy) --> NaOH + ¹/₂ H₂ + ¹/₂ Cl₂

The interfering reaction is simply
H₂O (+ electrical energy) --> H₂ + ¹/₂ O₂

Under standard conditions (1.0 M chloride solution), the first reaction actually requires a higher electrical energy input than the second (E₀ = 1.358 volt and 1.223 volt respectively), and so it is only kinetic factors that help the higher energy reaction to proceed -- probably preferential adsorption of chloride ions onto a fairly hydrophobic electrode (another good reason for using graphite). It is therefore essential to keep the chloride concentration high, well over 1 M. Probably the best way of achieving this is to have an excess of solid salt at the bottom of the cell that can dissolve to replace the salt that is being consumed.

From CliffordK:

Capture the hydrogen for "experiments", maybe in a mylar balloon.
Will the oxygen and chlorine come out together?

Yes they will come out together. That will not matter too much as a mixture of chlorine and oxygen gases is quite stable, but the mixture is much more dangerous in contact with hydrogen gas than either chlorine gas or oxygen gas alone would be.

I repeat that

When you get your electrode, Bmore, you may still have quite a lot of difficulty with the practical aspects of this electrolysis. It is an industrial method for producing caustic soda and chlorine gas known as the "chloralkali process". But it is not easily adapted for home, or even laboratory use,

[Lab Rat]

(1) Lab Rat elemental sodium is much more dangerous and much less accessible than caustic soda, which can be readily bought at appropriate stores (hardware stores in this country; do not know what British/North American equivalents are). If the aim is simply to get hold of some caustic soda, there is no need for electrolysis or any other awkward and dangerous chemical procedure, and certainly not to use an extremely dangerous material like metallic sodium. In my student days there was a man at my university who had permanent lifetime employment as a "cleaner" because he had been blinded and had bad facial scars from an accident where water had come in contact with NaK eutectic that was being used as a coolant in some particle physics equipment.

(2) Salt is not a catalyst in this electrolysis reaction, it is a reactant, along with water.


As for #1, I did warn that it was a dangerous reaction that would shoot off glowing debris.  The second one, however, was my mistake.