Making HCl

Hey Veeky Forums, I was wondering if you think it would be possible to make HCl (Hydrochloric acid) by following these steps:

1) Run electrolysis of saltwater, which will move the Cl- ions to the positive terminal where they will receive electrons and create Cl2 gass which I can collect into a tube.

2) Run electrolysis of regular water, creating O2 and H2 which I can take into a tube.

3) Meet the gasses and if needed, add heat to start the reaction that forms HCl(g) which will react with water in the air to create the acid which I can cool down to a liquid state.

I have a drawing of it which better describes it, but I can't post it right now. Do you think it will work? If not, what can I do to make it work without having any pre-existing acid?

Was also considering to attempt making it by mixing vinegar with salt, but I doubt the acid in vinegar is concentrated enough for that to work. Besides, after some equations I think that might return the Na and Cl ions making them act as catalysts instead of creating HCl

And also, which safety equipment would be necessary for creating just a small amount of this? Do I need to do it outside, do I need to wear eye protection, etc. All help is appreciated :)

>which I can collect into a tube.
This sounds tricky. Do you have the laboratory equipment required to collect and mix gases without losing them?

The only other methods I can think of to do this from scratch involve a bunch of sulphur reactions, so you probably have the simplest method. Bear in mind you may be able to produce both hydrogen and chlorine gas with the same electrolysis setup, potentially allowing you to perform the entire process with one set of apparatus, again if you have the means to capture the gases.

>Do I need to do it outside, do I need to wear eye protection, etc.
You're attempting to work with extremely hazardous chemicals, user. In these circumstances you should ALWAYS wear eye protection and ALWAYS work in a ventilated area.

First of all, thanks for the amazing response!

Now to answer your question, I have some equipment I could probably set up to do it half-assed, but if it is possible to create chlorine and hydrogen gass from the same electrolysis this would be alot easier. I could put a glass tube thing(I do not know what it is named in english, it's the most basic glass equipment in chemistry which is a cut out tube piece which you can use to store things in, I'll just call it reagent tube). I could do this:

1) Put the reagent tube in the salt water.

2) Fill it with salt water and lift it above the surface, since the salt water has to stay in it to not create a vacuum the salt water will now be standing up above the other salt water.

3) Put the electrodes up in the tube from below and power them up. The Hydrogen gass will come from one side and the Chlorine from the other, and they will mix with each other then the water. The acid will be diluted in the water and I haven't thought about how to solve that yet, but anyhow do you think this will work in principle?

This should also make it easy to test if it works or not. If it does work the gasses will not fill up the reagent tube, but rather react and make the water more acidic.

More thoughts: the mixture of hydrogen gas and chlorine gas at any real concentration could be explosive. It's definitely exothermic and the reaction may be spontaneous.

If you still want to go through with it for some reason, you can do it with a single electrolysis reaction in brine, with chlorine produced at the anode and hydrogen at the cathode. You could put both electrodes in the same gas capturing vessel submerged in solution, have the caught gas mixture somehow react without generating stupid temperatures very fast, then bubble that through water to produce your acid (and even more heat).

The whole deal seems somewhat reckless, though. What do you want the acid for?

>and they will mix with each other then the water.
I forgot about this. You'll probably need a curved tube or something to prevent this, since the same reaction that's producing hydrogen gas is also producing sodium hydroxide, hydroxide anions replacing the negative charge on the chloride as it becomes chlorine gas. This will neutralise any acid as it forms, and the whole reaction will just produce a lot of heat (!!).

Better to keep the electrodes separate, running the evolved gases through separate tubes into a mixing vessel elsewhere.

Actually for nothing right now, this is for my chemistry class. Just wanted to learn how to make one of the most used chemicals in chemistry, which might impress the teacher a bit.

And for reckless, I probably wont do it if it explodes. May I suggest a way to cause the process to go slowly and not explode-ly:

1) Fill the reagent tube with salt water while under the salt water and put the diodes up into it.

2) Submerge it completely in the salt water so that it does not heat up too much, and turn on the power, but not too much.

3) The Hydrogen and Chlorine gass immediately reacts, creating HCl and heat. The heat is distributed to the surrounding liquid and most of the HCl gass reacts with the salt water to make the acid.

I hope that doing this slow enough will make less heat, but making the acid slower which is no problem for me. What do you think?

Just take some table salt and sodium bisuphate. Mix and heat. Take precautions. Amount of both should be 1:1. Probably the easiest way. This is the only thing that went through my mind.

>since the salt water has to stay in it to not create a vacuum the salt water will now be standing up above the other salt water.
You should also be careful doing this, since the gases you're forming will be pushing against water and glass, adding pressure. Better to do it in a vessel filled with air or nitrogen, probably. Also, chlorine trapped in the presence of water will probably react to form a mix of hydrochloric acid and hypochloric acid, whether or not there's any hydrogen around, which might not be what you want.

If you're going to do this, be sure to do it at night or indoors. Hydrogen gas reacts explosively with chlorine gas. It's so reactive, that you only need a UV light as a source of energy. Depending on where you live, this could pose a problem.

I would recommend that you instead use this method:

electrolyze saltwater and run a tube from the positive terminal to a jug of water.

I've don't this myself and the process is extremely easy.

Basically, the reason why this works is that Cl is very reactive. When you add Chlorine gas to water, it rips the water apart to form bonds of its own. However, you will at first produce HClO instead of HCl. This compound will naturally dissociate, but can be accelerated with the use of sunlight. Because of this, do not cover your jug or glassware with a cork or cover. Once the HClO dissociates, O2 gas will be released and quickly fill up the container.

Be sure that you're only collecting the Cl gas when you do this.

Great idea! If I used a sort of M tube that goes back into the water, where the gasses would react, the heat would probably not be a big problem. Only problem then would be that while Chlorine is heavier than air, Hydrogen is not. The hydrogen would be at the top of the M until it filled up it's part entirely, while the Chlorine would lay at the bottom of the M waiting for the Hydrogen. Also, if that happened there would be a considerable amount of concentrated Hydrogen waiting for being ignited, which could be a very big problem if it did.

So yea never mind... Any design ideas that don't blow up?

Where do I find sodium bisuphate? Sorry I read about it, but I'm not good with baking and that seems to be where you find it mostly. Any specific products I can get which contain alot of it?

Yeah this would work. Got any hydrogen sulphates? You'd need sulphuric acid to make it from scratch, though.

Buy it online, it's not too expensive.

Well hypochloric acid isn't really mentioned in the current chapter, so it wouldn't be relevant that much, but I guess if I can filter it out I could use it to make hydrochloric acid too.

Maybe something like this:

1) Bubble the Chlorine through the water making Hydrochloric acid and hypochloric acid.

2) Isolate them, giving me a bit of hydrochloric acid and hypochloric acid in another container.

3) React hypochloric acid with Cl- iones, which it will give it's H+ iones too creating more hydrochloric acid.

Does the Hydrogen gass come out from the positive or negative electrode though? If it comes out from the negative one this will be way easier than if it doesn't. I actually already had a plan on how to concentrate Cl2 only.

Dunno, not unless I can buy them from some normal store. I don't really want to blow a whole lot on this, my budget isn't too big.

...I think you need to spend a few more years learning basic chemistry, user.

Sorry man, I just want to be sure. I know the Cl ions goes to the positive electrode because they are negative, but what is the Hydrogen?

Let me guess though, does the water's own protolysis make it so that the H+ ions goes to the negative electrode? I'm probably wrong, but since you know it why don't you tell me so that I can get smarter and get better grades? :)

Also here's the setup which I initially thought about using, but it's highly impractical and I don't think it's a very good idea now that I've learned that this will most likely explode. Any ideas on how to make it better?

Whoops, here's the picture.

It would be very painfull

Not planning to blow myself up or spill acid on my skin.

You always need eye protection, also by thicker gloves just in case