Sciencemadness Discussion Board - HCL from Cl2 and H2O

HCL from Cl2 and H2O

ThatChemist89 - 15-9-2024 at 15:28

Hey everyone

I'm trying to figure out how to decompose hypochlorous acid using UV light. I've seen that Cl2 + H2O yields HCl and hypochlorous acid, and I know UV light can help break down the hypochlorous acid.

Has anyone tried this before? If so, could you share your experience and any specific instructions or tips? I already have a chlorine gas generator.
I do not trust my self.

Rainwater - 15-9-2024 at 17:11

The experments ive watch on tv used Cl2 and H2 gas. When exposed to a specific wavelength of light, boom.
I'm not sure why you would need to make HCl from Cl2, but if you bubble it into water and give it time to be absorbed or dissolved, you will have consentrated HCl.
The hypochlorous acid is a different beast. There is an equilibrium in water that will cause the acid to convert back into Cl2, but it's basically pure bleach and great at removing the toughest noble metals like gold and platnium.
I think all HCl solutions contain hypochlorous acid but I could be wrong.

chornedsnorkack - 15-9-2024 at 21:04

Quote: Originally posted by Rainwater

I think all HCl solutions contain hypochlorous acid but I could be wrong.

Flagrantly wrong. HClO is a strong oxidant, which HCl is not. It takes strong oxidization to get any HClO (or Cl₂) into HCl.

woelen - 16-9-2024 at 23:39

Quote: Originally posted by Rainwater

[...] if you bubble it into water and give it time to be absorbed or dissolved, you will have consentrated HCl.[...]

This is wrong. You won't be able to make concentrated HCl from chlorine and water. Chlorine dissolves in water, but only around 10 grams per liter. If there is chloride present, then the maximum possible concentration goes down even further. With Cl2 and water (and a strong UV-source) you may get a few percents of HCl, but that already will be very hard and the process will be slow and tedious. Simplky said: making HCl from Cl2 and water in practice is a bad way to make HCl.

Precipitates - 17-9-2024 at 01:30

I wondered about the possibility of bubbling Cl₂ into H₂O₂ to produce HCl.

The following thread makes for some interesting reading: Hydrochloric acid hydrogen peroxide mix

Quote: Originally posted by AndersHoveland

Indeed, hydrogen peroxide can actually reduce aqueous chlorine to hydrochloric acid. In water the net equation is,

H2O2 + Cl2 --> 2HCl + O2

Edited to fix the quote link.

[Edited on 17-9-2024 by Precipitates]

bnull - 17-9-2024 at 04:41

@Rainwater: You can always test them for hypochlorite. There's none, of course

@Precipitates: It looks like singlet oxygen. Is it right? (Saving the idea for later use.)

Other reducing agents could be used, such as Fe²⁺:$$2~Fe^{2+}+Cl_2 \rightarrow 2~Fe^{3+}+2~Cl^-,$$ or (an aqueous suspension of) zinc:$$Zn(s)+Cl_2 \rightarrow Zn^{2+}+2~Cl^-;$$ perhaps formaldehyde:$$HCHO+2~Cl_2 + H_2O \rightarrow CO_2 + 4~HCl.$$ The first two don't give HCl directly but at least Cl₂ becomes chloride, which is an improvement over HCl/HClO.

Why one would use formaldehyde to make practical quantities of hydrochloric acid just escapes me. Apart from being academically interesting, there are cheaper and better routes to it.

[Edited on 17-9-2024 by bnull]

Rainwater - 17-9-2024 at 11:28

My stoichiometry for refining IrCl₂ is all messed up then.

RU_KLO - 17-9-2024 at 11:29

Here is some "old" information,

During the investigation in this laboratory of the absorption of chlorine by various kinds of charcoal, it was found that the moisture content of the gases coming in contact with the charcoal at room temperature greatly influenced not only the rate of absorption but also the nature of the phenomenon.

When the chlorine-air mixture is dry the chlorine is removed from the air and is retained by the charcoal, while with moist gases a chemical change
takes place that is manifested by a reaction between the water and the chlorine in the sense of the equation

2Cl2 + 2H2O + C = 4HCl + CO2

(it seem that passing wet chlorine gas thru carbon, makes HCl)

The reaction is very satisfactory in that all of the chlorine may be converted into hydrochloric acid but very disappointing in that the oxygen does not appear as such, but, as might be predicted, unites with the carbon. The formation of hydrochloric acid has been found to proceed over a very wide temperature range above 80. C., preferably between 80' and 200°, and
large quantities of chlorine can be handled in a comparatively small
apparatus.

The best procedure is to blow the steam and chlorine through a large bed of charcoal of the character used for absorbing gases-coconut charcoal, ivory nut charcoal, and other varieties especially treated-and at the same time small quantities of air may be admitted to assist in sweeping out the products of the reaction. The process is highly exothermic and the excess of water and air carries off the heat generated in the catalytic mass.

THE PRODUCTION OF HYDROCHLORIC ACID FROM CHLORINE AND WATER
By H. D. Gibbs

Attachment: HCl - de Chlorine y water.pdf (551kB)
This file has been downloaded 57 times

Precipitates - 17-9-2024 at 18:06

Quote: Originally posted by bnull

@Precipitates: It looks like singlet oxygen. Is it right? (Saving the idea for later use.)

The solution must have a proton absorbent present e.g.,. pyridine, to produce singlet oxygen.

"Further, with H2O being a much weaker base than F−, the H2O2–H2O system is unable to react with Cl2 to produce O2(1Δ)."

Production of singlet oxygen by the reaction of non-basic hydrogen peroxide with chlorine gas

khlor - 22-9-2024 at 07:38

Hello, sorry I'm late to the party, however, I do have a few things to help you.

first what you are trying to do has a name(it is wet chlorine route)
second, there are posts here on SM froum with lots of helpful information about it, here are my picks:

https://www.sciencemadness.org/whisper/viewthread.php?tid=15... - This guy actually managed to produce fuming HCl Solution with a UVC lamp, Cl2 and water and he has a youtube channel with video to prove.

https://www.sciencemadness.org/whisper/viewthread.php?tid=21...

https://www.sciencemadness.org/whisper/viewthread.php?tid=12... - This one is really good

https://www.sciencemadness.org/whisper/viewthread.php?tid=15... - This is my own deep dive on the subject

I do recomend following this order and reading all posts on theses threads and it will give you an idea of weather you want to tackle it or not, it is not efficient, nor fast or easy, however it sure tought me a lot and it is interesting, after all, exploring the science is our goal here.

[Edited on 22-9-2024 by khlor]

Quote: Originally posted by woelen

True, I 100% agree, but c'mon, it is a bad way to make HCl(I tried myself for science, so I know) but if he wants to explore science it is not a bad way to spend time, and improve know-how to apply on other projects, it is simple and complex enough for that and heck, I had a lot of fun with it.

[Edited on 22-9-2024 by khlor]

woelen - 22-9-2024 at 23:09

Oh yes, if you have scientific/academic interest in the properties of chlorine and want to explore its chemistry, then of course, that can be a rewarding endeavor. Actually, most of the experiments I did, were for this reason! But if your goal simply is to get HCl at decent concentrations and purity, then there are much better ways to achieve that, even in an amateur/home lab setting.

[Edited on 24-9-24 by woelen]

bnull - 23-9-2024 at 05:18

Quote: Originally posted by khlor

but if he wants to explore science

What @ThatChemist89 wants is to make HCl because it is hard to find wherever he lives. And he probably wants to use it to explore science afterwards.

By the way, the links are interesting. Thanks.