Preparation of HCl

[The Cancer Curer]

I had a question on the formation of HCl.

Would this work:

NaCl + NaHSO₄ HCl + Na₂SO₄

Procedures:

1. Mix NaCl with NaHSO₄ obtained from pool supplies
2. Distillation of HCl from Na₂SO₄
3. Distilled HCl into an ice bath to condense to liquid
4. Store HCl in freezer

Questions:

1. Is the freezing point of HCl -72^oC and -8^oF?
2. If a freezer is approximately 0^oF, would just -8^oF keep the liquid from actually freezing?
3. Is there a better way to store HCl at home?
4. Are there any reactions that could take place in this experiment resulting in extreme injuries?
5. How pure would this substance be?

Thanks.

P.S. If this breaks forum rules (which I don't think it does), I'm sorry - just curious!

[nj_bartel]

I don't think bisulfate is nearly strong enough of an acid to protonate chloride.

[CopperSmurf]

A few pointers:
1) I highly doubt you'll make a strong acid from an even weaker acid.
2) HCl will tend to enter aqueous solution, so it won't be very pure (if you make any at all)
3) if you ever dealt with any pure strong acids, you'll know it'll burn
4) Any strong acid is dangerous!
5) Why bother making it at home? That makes it even more dangerous! If you're going to do any real research, just go out and buy it from a chemical supplier, it's an industrial chemical.

[The Cancer Curer]

5) Why bother making it at home? That makes it even more dangerous! If you're going to do any real research, just go out and buy it from a chemical supplier, it's an industrial chemical.

What's the dangerous fun in buying it? 

Alright, I guess I won't try it! Third dangerous idea...fail. 

Thanks for your replies nj_bartel and coppersmurf. Treats all around. 

[408]

OK, Time to clear some stuff up.

This will work to some degree.  The Golden Book of Chemistry Experiments(I think this was the manual that does this) uses bisulfate in place of concentrated sulfuric acid reacted with NaCl to produce HCl gas.

Grind the two together as solids and heat.  And heat means melt.

The chemistry stating that one needs a stronger acid to protonate a conjugate base of a weaker acid is mostly valid in terms of equilibrium constants in aqueous solution.  When you have solid/molten phase reactions, the driving force is removal of the volatile HCl formed, continually shifting the equilibrium toward the HCl side.

So get a vessel safe for both high temp and acids, mix your bisulfate and salt, and lead a tube from this sealed vessel into cooled water.  You WILL NEED A TRAP IN THE GAS LINE.  Suckback means boom here, as any suckback will instantly boil, perhaps overpressurizing your container.

Do not bother trying to collect pure liquid HCl at home, you sound too new at this.  I know many whom I would trust not to gas themselves while doing this, but as you are asking about the precautions to take doing this, you are not ready.  Just make the aqueous solution that all labs use anyway.  

You will want a well sealed bottle to store it in.  I would prefer outdoor storage, as the fumes seem to get through everything and rust things in the vicinity.

Injuries possible: minor acid burns, thermal burns from high temp reaction, and potential of everything blowing up in your face if you do not use a trap!  Oh and gassing yourself.

Purity: Probably rather pure, you are distilling a volatile substance out of nonvolatile ones.  Concentration depends on how long you bubble the HCl gas through the water.  Extreme overheating( a glass vessel would melt/soften before this became an issue) could be decomposition to SO3.

I would be comfortable doing this at home, but only outdoors or in a decent fumehood.  It is not too dangerous if done on small scale.

[The Cancer Curer]

Do not bother trying to collect pure liquid HCl at home, you sound too new at this.  I know many whom I would trust not to gas themselves while doing this, but as you are asking about the precautions to take doing this, you are not ready.  Just make the aqueous solution that all labs use anyway.  

Yeah, I mean I am new...which is why I am taking the precautions of asking if something is safe and/or how to do it in a safe way. Don't get me wrong - I'm not stupid, if something seems too dangerous, I'm not going to attempt it without professional supervision (until I know how to do something for sure). 

Injuries possible: minor acid burns, thermal burns from high temp reaction, and potential of everything blowing up in your face if you do not use a trap!  Oh and gassing yourself.

Hmmm....maybe I'll stick to studying. 

Thanks for the information!

[nj_bartel]

Cool stuff 408, thought there might be some kind of way to do it with equilibrium.  Would still much favor using conc. sulfuric though, assuming that's available

[The Cancer Curer]

Would still much favor using conc. sulfuric though, assuming that's available

Yeah, I would too...but you can't buy (well you can for a higher cost) sulfuric acid like you can sodium bisulfate (in pool cleaners). Its not readily available to me either so...

[408]

Yeah, I mean I am new...which is why I am taking the precautions of asking if something is safe and/or how to do it in a safe way. Don't get me wrong - I'm not stupid, if something seems too dangerous, I'm not going to attempt it without professional supervision (until I know how to do something for sure). 

I am not saying do not try to collect a aqueous solution of HCl.  Your question initially seemed like you were wanting 100% liquid HCl gas, which would only exist cold or under pressure.  But attempting this prep by leading the HCl gas into water to create an aqueous solution is safeish.  Just use a trap for the gas to prevent suckback.

I would never discourage someone from DIYing anything.  But I will tell what is involved.

Have fun!

[researcher]

what about

2 NaCl + H₂SO₄      Na₂SO₄ + 2HCl

[Borek]

You can write whatever reaction you want, it doesn't mean it will go in reality

[408]

what about

2 NaCl + H₂SO₄      Na₂SO₄ + 2HCl

That works better than the bisulfate method I outlined above, lower temperatures needed.
Of course, conc. sulfuric and solid NaCl are needed.  Aqueous solutions give you nothing.

[The Cancer Curer]

You can write whatever reaction you want, it doesn't mean it will go in reality

Shouldn't a reaction written out go if it is okay according to an activity series? - Besides different temperatures, pressures, etc. that could all cause a reaction not to go (is this what you mean?).

Thanks again 408!

[Borek]

Besides different temperatures, pressures, etc. that could all cause a reaction not to go (is this what you mean?).

Etc, etc, reaction doesn't have to go as is described by any single rule. In this particluar case - as it was discussed earlier - you need concentrated sulfuric acid and solid NaCl, this was not stated in the reaction equation.

Besides, why not

2HCl + Na₂SO₄ -> 2NaCl + H₂SO₄

pK_a1 for sulfuric acid is about -3, while pK_a for HCl is about -4, so HCl is a stronger acid...

[nj_bartel]

Weird... I was always under the impression that sulfuric acid had a pKa around hydrogen iodide.  Don't know where that misinformation came from.

[The Cancer Curer]

Weird... I was always under the impression that sulfuric acid had a pKa around hydrogen iodide.  Don't know where that misinformation came from.

Click pK_a Values Click

pK_a of hydroionic acid is -10 and sulfuric acid is -3.

Thanks Borek!

[researcher]

That works better than the bisulfate method I outlined above, lower temperatures needed.
Of course, conc. sulfuric and solid NaCl are needed.  Aqueous solutions give you nothing.

are you sure it doesn't work with aqueous solutions? I had read somewhere that the industrial method was with aqueous NaCl.

[408]

It may with concentrated solutions, followed by distilling out the aqueous azeotropic acid (~37%).  Dilute is likely useless for preparatory work(Unless industry has some odd method).  Using concentrated acid and solid NaCl is what I have seen in preparatory books for making solutions of HCl in various solvents.