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New Contributor

Need help understanding the production of Hypochlorous Acid and byproducts

The goal is to aid in the fight against COVID-19 by producing stable Hypochlorous Acid at 200 ppm FAC or more to sanitize hospitals and high touch places through the use of a fogger. HOCl is far more efficient than bleach and much safer. 

I am researching the creation of HOCl through the electrolysis of pure water with 40g of pure table salt NaCl per liter, with and without a Bipolar Membrane.

This is the best explanation of what happens that I have. But I am not sure it is correct. I feel there is more to it and more chemical compounds created.

2 NaCl + 6 H2O + Electricity = 2 HOCl + O2 + 4 H2 + 2 NaOH


2 NaCl + 6 H2O + Electricity = 2 HOCl + 2 H2O + 2 H2 + 2 NaOH

or simplified to

2 NaCl + 4 H2O + Electricity = 2 HOCl + 2 H2 + 2 NaOH

I especially need to know what gases are released at each end (Anode & Cathode). As they can be a safety hazard. I thought they were Oxygen O2 and Hydrogen H2. However several articles have referenced Chlorine being released. I thought it had to stick around to create the HOCl and if that is not true there is something very flawed with my equations above.

This diagram shows chlorine gas released at the Anode.

Chemistry of Hypochlorous Acid 

This site gives chemical equations I do not know how to read.

Electro-Chemical Activation 

This diagram shows Oxygen gas released at the Anode.

Fig. +. Schematic of electrolyzed water generator and resulting compounds.  | Download Scientific Di... 

This diagram also shows Oxygen gas released at the Anode.

What is HOCl? – eco-i-on 

This is a question-answer that clearly says Oxygen is not released. 

8 Replies
New Contributor

Re: Need help understanding the production of Hypochlorous Acid and byproducts

First off, hypochlorous acid is inherently unstable. Even sodium hypochlorite isn't particularly stable but hypochlorous acid is even more unstable.  Metals catalyze the decomposition of hypochlorous acid so any traces of metals will cause its decomposition. So if you're planning on making hypochlorous acid, you'll need to be using it soon after you've prepared it.

You will be better off adding some base to the sodium chloride. This will convert any chlorine gas produced at the anode to sodium hypochlorite. It will also stabilize any hypochlorous acid formed by converting it to sodium hypochlorite. You can then convert that to hypochlorous acid by the addition of HCl. But, you need to be careful that the pH doesn't drop to the point where it reverts to chlorine gas. Any pH below 5 will be problematic.

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New Contributor III

Re: Need help understanding the production of Hypochlorous Acid and byproducts

Alex, I  second Christopher's good advice about keeping the solution to pH greater than 5 (neutral or basic). If you were to go acidic, to pH <5, you would generate Cl2. Here are some thoughts about sanitizing high-touch places and about the chemistry involved.

First, about sanitizing in hospitals.The aqueous solution that you are spraying is 200 ppm HOCl (~4 x 10-3 M) and 40g/L (~0.67 M) NaCl. You will be leaving a solid residue, the salt. Is that OK? Hospital settings including emergency vehicles have a lot of electrical equipment, valves, and fine moving parts. Is it OK from a design viewpoint to use a salt fog and leave behind a solid residue? HOCl may well be OK from a personal safety viewpoint, but it's going to release Cl2 unless it's already reacted with the biologicals as intended, or with some of the equipment. Will that be OK at the concentrations you intend and with the ventilation available? The design and engineering are going to be important. You may want to look at what De Nora ( is offering as disinfecting equipment; their chlor-alkali technology is quite strong and it's an informative website.

As for "can I really make HOCl this way?" the answer is yes. For the work you are doing you may need to look at the chlor-alkali chapters in the Kirk-Othmer Encyclopedia of Chemical Technology or Riegel's Handbook of Industrial Chemistry. The references that perplexed you are true under some conditions but maybe not under the conditions where you will operate! 

Here is a short version why it's a real research project to get the conditions you want and the HOCl concentration you want for spraying. If you were electrolyzing pure water, the simple equations are:

         4H (aq)+ + 4 e- = 2 H2(g)                      at the anode

         4 OH-(aq)         = 2 H2O + O2 (g) + 4e- at the cathode

That's not the full story, though. At the anode you first get  

           OH-(aq)          =  OH. (on the cathode) + e-    You will want that OH radical to make HOCl.  Then

         2OH. (cathode) =  H2O2 that might desorb before it can make water.

If you electrolyze a concentrated salt solution, 350 g/L instead of the 40 g/L you want, you make Cl2 at the cathode:

         2 Cl-(aq)           = Cl2 (g)           + 2e-      That's two steps too:

            Cl-(aq)           = Cl. (cathode) +  e-         

If you electrolyze a 40 g/L salt solution as you intend, you produce Cl2 and also O2 at the cathode. Because you are making OH. and Cl. at the cathode, they can combine to make HOCl and go off in solution so you can spray it. As Christopher said, best to keep the pH at 5 or greater. If you go  more acid, you make Cl2 instead. If you go strongly basic (high pH) you get OCl-. It's quite a project!

Stay safe and God bless all here,

Mike Dowell

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New Contributor

Re: Need help understanding the production of Hypochlorous Acid and byproducts

The swimming pool industry has been doing this for years but for much lower concentrations of free available chlorine (FAC). Now some of the manufactures are adapting their products to make 200 - 1000 ppm FAC solutions.


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New Contributor II

Re: Need help understanding the production of Hypochlorous Acid and byproducts

I think one has to answer if the proposed cure is worse than the illness here?

Inhaling 200 ppm FAC mist during fogging is corrosive to lung tissue, eyes, skin, etc. plus damages equipment and finishes.   Swimming pool water is biocidal on the order of a few 1-3 ppm.  

Leave it to the experts, please.   The questions raised do not indicate a fundamental understanding of what is proposed to even carry out the experiments safely.   They are plenty of other common agents for this. 

Also chemists have responsibly here to respond responsibly as well.

New Contributor

Re: Need help understanding the production of Hypochlorous Acid and byproducts

I have a question.
What is the difference between creating hypochlorous acid and sodium hypochlorite.
I bought 2 different machines one produces hypochlorous acid and the other sodium hypochlorite.
But in both I use salt and water and both (I think) use the same generation system (Single Cell Electrolysis)
Maybe Im wrong thats why I am not understanding. Im searching in the web but none explain that.
Why one product or the other?
I hope you can help me.


New Contributor

Re: Need help understanding the production of Hypochlorous Acid and byproducts

Id be really interested to know the answers too...

New Contributor II

Re: Need help understanding the production of Hypochlorous Acid and byproducts

I would suggest you read the following:


Why Every Household Should be Using Hypochlorous Acid during the Pandemic
Hypochlorous Acid

What is Hypochlorous Acid?

Hypo-say what now? What is hypochlorous acid?

Hypochlorous acid is nature’s oldest disinfectant, and it happens to be walking around in about 7.5 billion people right now. As in inside all humans, this very moment. Why? It’s the substance your white blood cells produce to fight off infections. It’s also the active ingredient in electrolyzed water, which is an industrial technology used for green cleaning and sanitizing. Electrolyzed water is made when electricity is used to change the chemical structure of salt, water & vinegar into a disinfectant as effective as bleach, but with no harmful chemicals, fumes or residues. 100 times more effective than bleach, but totally non-toxic!
Pretty cool, right?

How is hypochlorous acid made?

To make hypochlorous acid is pretty simple chemistry. Start with precisely the correct proportions of three ingredients: salt, water, and vinegar. You may remember that a salt molecule is made up of the elements sodium and chloride (NaCl) and a water molecule is made up of hydrogen and oxygen (H2O). When an electrical current is applied to the solution, the molecules break apart and the elements form two new molecules:

Hypochlorous acid (HOCl)

Nature’s super powerful disinfectant, and also the ingredient that gives bleach its anti-microbial power. When the pH of the solution is lowered to the correct level, HOCl is created, exactly the same substance that is your immune system’s germ fighter. So when you take your child to that indoor play area/Petrie dish – your white blood cells get to work creating hypochlorous acid.

Sodium hydroxide (NaOH)

A common detergent used at different concentrations in everything from toothpaste to skin moisturizers to cleaning products. Because concentration levels vary so widely across products, so do toxicity levels. That’s why you can find this same ingredient in both tubes of toothpaste and drain cleaners.

Healthcare & medical uses of hypochlorous acid

Hypochlorous acid is so gentle that it has several uses in the healthcare and medical space. It’s FDA approved for use in wound healing, wound care, and eye care products and is also common in veterinary care products. It’s even used to eradicate biofilm. There has been extensive research on the gentleness and efficacy of HOCl when it comes to killing bacteria. It is so trusted and effective, that hospitals use it as a disinfectant in both the US and Japan.

Hypochlorous acid for disinfecting

Given how effective it is at killing microbes without leaving behind harmful residues, hypochlorous acid is also used for preserving fresh produce. It’s even USDA approved for use in organic crop production.

Making Hypochlorous Acid (HOCL)

The Eco One machine


Making disinfectant is easy. Just fill the pitcher with water and add kosher salt. Power on the system and within minutes a cleaner & disinfectant is generated called hypochlorous acid (HOCl) also known as electrolyzed water.

Alternatively, a cleaner & degreaser can be generated by substituting kosher salt for food-grade potassium carbonate.


Since the start of the COVID-19 pandemic, many low-quality hypochlorous acid generators from China have flooded the market. It is important to understand why quality is important. Below are some key points to consider before making a purchase:

Titanium Electrolysis Cell - The cell must be manufactured with a high-grade titanium coating. Systems using electrolysis cells that are manufactured from lower quality alloys will deteriorate quickly and may not be generating hypochlorous acid. If the electrolysis cell is made from steel or other lower grade metals, the electrolysis cell will deteriorate very quickly and will generate harmful chromium compounds that can be carcinogenic.
Size of the Electrolysis Cell - Our electrolysis cell is relatively large for a 1 Liter pitcher and only requires 2 grams of salt to generate 200 ppm of hypochlorous acid. Even higher concentrations can be generated if the system is run for extra cycles. Many low-quality systems manufactured in China are requiring very large quantities of salt. If you see that the directions on a system require 5 to 20 grams of salt per Liter, you can be sure that the electrolysis cell is very small and your solution salinity will be extremely high. Most likely the system is generating sodium hypochlorite (NaOCl) and not hypochlorous acid (HOCl).

Concentrations up to 200 ppm of hypochlorous acid (HOCl)
Production Rate (Setting 1): 1 Liter at 40 ppm in 3 minutes
Production Rate (Setting 2): 1 Liter at 60 ppm in 5 minutes
Production Rate (Setting 3): 1 Liter at 100 ppm in 8 minutes
Production Rate (Setting 3): 1 Liter at 200 ppm in 16 minutes

Oxidation Potential of Anolyte (HOCl): +800 to +1000 mV

Concentrations over 400 ppm of hypochlorous acid (HOCl)
After generating 200 ppm, if you continue to run additional cycles on setting 3 (8-minute cycles), each additional cycle will raise the concentration by approximately 80 ppm.
Production Rate (Setting 3): 1 Liter at 400 ppm in 40 minutes (five 8-minute cycles)


The electrolysis cell is manufactured in titanium and has a typical lifespan of 3,000 cycles (8 minutes each).


Model: E1
Electrolysis Cell: Titanium
Power Supply: 110V/220V, 50/60Hz
Dimensions: 21 x 15 x 36 cm (8.3 x 5.8 x 14 inches)
Weight: 0.6 kg (1.3 lbs.)


Eco One System
Power Adapter (US Plug)
1 gram measuring spoon
User Manual

What about the salt for making HOCl disinfectant?
You will need to purchase non-iodized food-grade salt at your local supermarket (ie. kosher salt).

What about the potassium carbonate for making KOH degreaser?
A 100-gram sample of food-grade potassium carbonate is included, enough to generate 50 liters of degreaser.

In summary, Hypochlorous Acid is the weapon of choice in fighting Covid-19 and a whole host of other pathogens.

For more information, products, and/or to purchase the Eco One click on this link:

I am an affiliate of this company/product because I personally use it and am convinced of its value and effectiveness.

Stephen Brackens Brinkley


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New Contributor II

Re: Need help understanding the production of Hypochlorous Acid and byproducts

What I would like to very much know! Please, no speculation or just opinions, I am looking for hard facts based on actual research.  Thank you.


1.  Does the Eco One machine produce true HOCL and, if so, for how long is the solution effective against pathogens? 

2. Is the addition of acetic acid absolutely essential to the eco one process to produce HOCL, and, if so, should the acetic acid be added before or after the electrolysis?