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HCl obtention from bleach and acetic acid (vinegar). Answered

I have always been curious to know if it is possible to obtain hydrochloric acid (HCl) from chlorine-based bleach and acetic acid (vinegar). I found a lot of answers saying that it was impossible and dangerous because you wouldn't obtain HCl; instead, you would get chlorine gas, which is a very dangerous fume that can cost your life. However, I found an answer saying that it was possible to synthesize it, but not directly from bleach. First, you have to mix equal quantities of bleach and acetic acid to obtain hypochlorous acid (HClO) and then you have to add a transition metal oxide (iron oxide, copper oxide, etc.) to get HCl and oxygen gas. 

Filled with curiosity and keeping in mind that safety is the priority, I decided to try it out by mixing equal portions of bleach (NaOCl) and acetic acid (C2H4O2), obtaining an aqueous solution of hypochlorous acid (HClO) and sodium acetate (C2H3NaO2). 

NaClO + C2H4O2—> HClO + C2H3NaO2

Then, I added copper oxide (rusty pennies) since I know that copper by itself reacts very slowly with HCl, so I could leave it there until the copper oxide had completely reacted with the HClO (leaving clean pennies). 

Little but numerous bubbles started to come out which I thought to be the oxygen gas leaving the hypochlorous acid. I waited there until there were no more bubbles coming out which meant that the reaction had finished.

To prove that it was HCl, I decided to add Aluminium foil and see if it reacted accordingly. However, nothing happened, so I tried the whole process of mixing bleach and vinegar again but when I got to the part of adding the metal oxide, I did not add copper oxide. Instead, I left it outside in the sun to react since I know that ultraviolet radiation causes fast disproportionation, forming HCl and oxygen gas.  

HClO —> HCl + O2

After all the bubbles had finished coming out, I added Aluminium foil to prove that it was HCl. However, noting happened, and again, I obtained the same product as the last time. 

I immediately stated to think of possible products that I could have obtained and the reasons why my reaction hadn't worked properly. It was then when I remembered that in the very first reaction (the one of the vinegar and the bleach) I had obtained a side product that I had completely forgotten about; sodium acetate (C2H3NaO2). And I suspect that this side product could have affected the whole process. 

And that is my question; was it really the sodium acetate that one that affected the experiment or could have it been something else?



4 months ago

Well, I can buy it from the hardware store but if I would have to make it myself I would use salt and concentrated sulfuric acid.
Still produces some toxic chlorine gas in the process but it provides a clean acid.
The traditional way of dissloving chlorine gas in water works fine too but it is a pain to keep a closed loop system with household materials.


4 months ago

You probably need to distill the end product. As it is, the concentration is most likely very low. This leads to decreased acidity and slower reaction times. I'm not a professional chemist, so don't be upset if I'm wrong. ;-)

Jack A Lopez
Jack A Lopez

2 years ago

I do not know why your experiment did not work.

Although it seems like there has to be an easier way to make homemade hydrochloric acid, if that is the goal here.

Starting with hypochlorite ion, ClO-, seems like trouble, because I think the chlorine atom in that is in a +1 oxidation state, and you want to reduce that to -1, i.e. chloride.


I think the usual, textbook recipe for hydrochloric acid, starts with a chloride salt, typically sodium chloride, plus a strong acid, like sulfuric acid.

NaCl + H2SO4 = NaHSO4 + HCl

I copied that reaction from the Wikipedia article for "Hydrogen chloride",


Would the same reaction work with a weak acid,like acetic acid, in household vinegar?


I dunno. Using electrolysis to make chlorine gas from aqueous NaCl, that is pretty easy, although at the beginning of your post you maybe said you wanted to avoid Cl2 gas.

By the way, HCl is pretty nasty in gaseous form too, and I think some of these reactions (like NaCl + H2S04) will tend to produce it that way. Also I think aqueous HCl spontaneously releases HCl gas, like it spontaneously "boils out", but the rate at which it does so, depends on temperature, and concentration of the aqueous HCl.

In fact, I recall seeing, as a Youtube video, a method for purifying hydrochloric acid, and that method was just to put a container of aqueous HCl, and a container of pure water, next to each other, in a closed container big enough to hold both of them. This magic is made possible by gaseous HCl moving through the air, at room temperature.

That video should not be too hard to find. I think it was this one.