Making Sodium Chorite from NaCl Solution and Electrolysis

Chemistry and homework help forum.

Organic Chemistry, Analytical Chemistry, Biochemistry, Physical Chemistry, Computational Chemistry, Theoretical Chemistry, High School Chemistry, Colledge Chemistry and University Chemistry Forum.

Share your chemistry ideas, discuss chemical problems, ask for help with scientific chemistry questions, inspire others by your chemistry vision!

Please feel free to start a scientific chemistry discussion here!

Discuss chemistry homework problems with experts!

Ask for help with chemical questions and help others with your chemistry knowledge!

Moderators: expert, ChenBeier, Xen

Post Reply
yerrag
Full Member
Full Member
Posts: 12
Joined: Sun Oct 07, 2018 7:39 pm
Location: Manila

Making Sodium Chorite from NaCl Solution and Electrolysis

Post by yerrag »

I came across this article that shows how to make sodium chlorite from sodium chloride in a water solution using electrolysis:

https://sciencing.com/make-sodium-chlorite-5188671.html

The reaction should look like this, according to the Chemical Equation Balancer:

https://www.webqc.org/balance.php?react ... aClO2%2BH2

NaCl + 2H2O = NaClO2 + 2H2

Is this possible?

I finished the process last night, and I got a solution with a lot of black precipitate, which was from the carbon plates I used. It came from the anode carbon plate. Half of the carbon plate (attached to the positive 12v terminal of my AC-DC converter) was leached off and caused black precipitates.

When I filtered the solids off the final solution, all I could see was black. I wasn't sure if there were any sodium chlorite in it. Maybe I should have used a pencil, as originally instructed, as I won't expose too much carbon and this may lead to less leaching of carbon into the solution.
yerrag
Full Member
Full Member
Posts: 12
Joined: Sun Oct 07, 2018 7:39 pm
Location: Manila

Re: Making Sodium Chorite from NaCl Solution and Electrolysis

Post by yerrag »

watched this video :

https://youtu.be/1nAe_T5mO2o

I think I have some ideas:

1. Lower voltage to 3v. This will conserve the erosion of carbon electrodes that dirty the water. But more importantly, it may keep the voltage from going to a point where it provides enough energy needed to make chloride ions turn into chlorine gas, as I need to have the chloride ions available to make chlorite ClO2-

2. Continue to use the graphite rods. It's still better than lead, which will not erode as fast but is toxic. And platinum is too expensive.

3. Lower the pH of the solution of HCl. This will favor the reaction involving the breakdown of water into hydrogen and oxygen molecules, instead of the reaction involving the chloride ions turning into chlorine molecules that leave the solution into the atmosphere.

4. Lower the concentration of NaCl in the solution, if needed, as this favors the breakdown of water into hydrogen and oxygen, and not the one involving chlorides ions turning into molecular atmospheric chlorine.

I have no idea how much HCl to use, but I imagine it won't be too much as long as it favors water breaking down into H2 and O2. I may just try making this one change.

I just hope that the chloride ion will be able to react with the oxygen and form ClO2. I still have to find out what reactions are involved in making the Cl- and O2 turn into ClO2. Does anyone know what how chloride ion turns into chlorite ion? Does it first become hypochlorite ClO- before becoming ClO2-? If so, what is needed to make the full reaction happen?
User avatar
ChenBeier
Distinguished Member
Distinguished Member
Posts: 460
Joined: Wed Sep 27, 2017 7:25 am
Location: Berlin, Germany

Re: Making Sodium Chorite from NaCl Solution and Electrolysis

Post by ChenBeier »

Important is to stirr very good. Why?
You will not develop ClO2 that is different from ClO2-.
The right electrode material is important. No blended carbon. It has to be pure graphite.
The other things already mentioned, like voltage and current,concentration, etc.
Also addition of baking soda or caustic soda helps.
yerrag
Full Member
Full Member
Posts: 12
Joined: Sun Oct 07, 2018 7:39 pm
Location: Manila

Re: Making Sodium Chorite from NaCl Solution and Electrolysis

Post by yerrag »

mportant is to stirr very good. Why?
You will not develop ClO2 that is different from ClO2-.
I did not know this. Thanks.

Why does stirring keep from producing chlorine dioxide?

Also, where can I get information on the potential (voltage) involved in dissociation/association reactions?
yerrag
Full Member
Full Member
Posts: 12
Joined: Sun Oct 07, 2018 7:39 pm
Location: Manila

Re: Making Sodium Chorite from NaCl Solution and Electrolysis

Post by yerrag »

Here's what I've come up with on the process:

First, heating the sodium chloride in water ensures that:

NaCl = Na+ + Cl-

Then,

2Cl- = Cl2 + 2e- (-1.36v needed; Cl2 is released into atmosphere- I hope I can minimize this as I need the Cl-. Any ideas?)

Followed by both these 2 reactions:

4H2O + 4e- = 2H2 + 4OH- (from 2H2O + 2e- = H2 + 2OH- using -0.83v)
Cl- + 4OH- = ClO2- + 2H2O + 4e- (using 0.78v)
____________________________
2H2O + Cl- = ClO2- + 2H2 Net

It should be noted that the highest voltage needed needed is 1.36v only. Limiting the voltage to say, 1.5v would keep other reactions from happening that would increase the change of reaction outcomes. Such as:

2H2O = H2O2 + 2H+ + 2e- (this requires -1.78v; this is a required first step before water can break into H2 + O2)

By not allowing water to turn into H2O2, the electrolysis of water into H2 and O2 is avoided. This, I think will lessen the carbon anode from being oxidized and keep carbon particles also from eroding into the solution.

I have an AC-DC converter that allows me to choose voltage of 3, 6,9, and 12v DC. If I switch to 3V, I'm still above the voltage of 1.89v. I may just need to use a resistor to lower the voltage to a level that keeps O2 from being produced. Preferably, a rheostat would be needed so I can easily fine-tune the voltage to where I can see minimal bubbling of O2 at the anode.
yerrag
Full Member
Full Member
Posts: 12
Joined: Sun Oct 07, 2018 7:39 pm
Location: Manila

Re: Making Sodium Chorite from NaCl Solution and Electrolysis

Post by yerrag »

2Cl- = Cl2 + 2e- (-1.36v needed; Cl2 is released into atmosphere- I hope I can minimize this as I need the Cl-. Any ideas?)
I wonder if instead of this reaction, I could add an electron donor to the solution. What electron donors can I use?

Would methylene blue do? I'm just thinking this, only because I know methylene blue as an electron donor, but I'm just throwing an idea to see if someone more knowledgeable can tell me it's not possible. But if I can do away with the reaction that makes chlorine gas from chloride, I would be able to further lower my required voltage to below 1v.
User avatar
ChenBeier
Distinguished Member
Distinguished Member
Posts: 460
Joined: Wed Sep 27, 2017 7:25 am
Location: Berlin, Germany

Re: Making Sodium Chorite from NaCl Solution and Electrolysis

Post by ChenBeier »

First sodium chlorite is not possible to obtain by electrolysis. What you get is sodium hypochlorite NaClO. The procedure in your link will give this not sodiumchlorite. It is a mistake there.
In this environment Peroxide will not developed. The chlorine can be absorbet by caustic soda I mentioned already. You produce it at cathode side anyway, so good stirring is necessary or extra add.

2 Na+ + 2H2O + 2e- => 2 NaOH + H2 cathode
Cl- + 2 NaOH => NaClO + Na+ + H2O + 2 e- anode

Sum Na+ + Cl- + H2O => NaClO.+ H2
yerrag
Full Member
Full Member
Posts: 12
Joined: Sun Oct 07, 2018 7:39 pm
Location: Manila

Re: Making Sodium Chorite from NaCl Solution and Electrolysis

Post by yerrag »

Thanks.

I can see now I'm not doing it right. There has to be a simultaneous reducing (at anode) and oxidizing (at cathode) process to make this work.

Have forgotten my physical chemistry classes as this was long ago.
Post Reply