Sciencemadness Discussion Board

Making Hydrochloric acid

Manifest - 8-1-2013 at 13:07

Hello, I am looking to make Hydrochloric acid from the Salt/Sulfuric acid method.

I must ask. Is this worth it? How much acid am i getting from using more acid?

Also. I have some toilet unblocker that has 8% HCL in it.
So I'm thinking hey, why not heat that up and disperse it in water.
Or maybe if there is an easier way to concentrate it I'm all ears.

AndersHoveland - 8-1-2013 at 13:24

I bought 27% muriatic acid at the hardware store. Sometimes you have to search around to see what different stores have.
It is also commonly used for pools... I think one time I might have 'borrowed' some from the back room at a community pool, someone forget to lock the door... :)

[Edited on 8-1-2013 by AndersHoveland]

elementcollector1 - 8-1-2013 at 15:17

There are more than a few ways to make pure hydrochloric acid, of varying concentrations.
For the salt/sulfuric, the reaction does occur without heating, but you get a very weak product. With heating, but not boiling, the reaction is allowed to proceed to completion (make sure you have a suckback trap!!)

Another, easier but more time-consuming way is to take a container of impure HCl, and a container of pure distilled water, and set them in a larger, airtight container, and close the larger container. Over time, the HCl will go into equilibrium between the impure and the pure (for example, if you used your 8% stuff, you should get around 4% pure HCl. This can be concentrated by distillation, I think. Or boiling (though the offgassing of HCl worries me, both for your safety and your product).

AndersHoveland - 8-1-2013 at 15:27

Another way is to mix some dilute sulfuric acid with CaCl2. The CaSO4 has a low solubility so, if mixed in the exact stoichiometric ratio, it should leave mostly hydrochloric acid in solution, if the impurities are not a problem.

Another way is leaving a solution of chlorine in sunlight. (while oxygen does generally have more affinity for hydrogen than chlorine, the reaction can still proceed, very slowly though) The net reaction in sunlight is:

Cl2 + H2O --> 2 HCl (aq) + O2

[Edited on 8-1-2013 by AndersHoveland]

Adas - 9-1-2013 at 09:11

You wouldn't have to use suckback trap if you lead the HCl gas into a balloon and then dissolve it in water. The sulfuric/salt method is probably the best, you will get NaHSO4 as a byproduct, which you can use for other reactions.

Poppy - 9-1-2013 at 16:04

I confess I tried the old trick again, calcium chloride plus sulfuric acid, stoichometrically insubstatial, in principle, thus a lot of water was added. Hopefully it will decant the gypsum in the bottom half thus allowing for the upper part separation of 12% hydrochloric acid w/w. If it hopefully decants then 12% at least seems stronger than sulfuric acid for many applications.


EDIT: this method is total crap and won't ever ever work, even diluted this way, all you get is a silly putty.
Perhaps that might somehow work with Barium sulfate.


[Edited on 1-10-2013 by Poppy]

woelen - 9-1-2013 at 23:46

Another good method, using OTC chemicals only is to use swimming pool pH-minus (which is nearly pure NaHSO4.H2O) and table salt and heat this mix. Mix appr. stoichiometric equal amounts (some excess NaHSO4.H2O is OK) and then heat the mix. NaHSO4.H2O melts in its own water of crystallization at only 60 C or so and if you continue heating this mix, then a mix of water and HCl comes over. Lead this through water and you get your hydrochloric acid. The remaining solid material is impure Na2SO4. From this you can crystallize quite pure Na2SO4.10H2O by dissolving it in water and slowly letting the water evaporate.

Manifest - 10-1-2013 at 09:04

I like the sulfuric acid and Calcium Chloride method.
However Poppy did you say it didn't work for you?

AJKOER - 16-1-2013 at 16:14

I believe I have previously referenced in another thread from Watt's Dictionary Chemistry that Oxalic acid heated with NaCl produces HCl (gas).

Quote: Originally posted by AndersHoveland  

Another way is leaving a solution of chlorine in sunlight. (while oxygen does generally have more affinity for hydrogen than chlorine, the reaction can still proceed, very slowly though) The net reaction in sunlight is:

Cl2 + H2O --> 2 HCl (aq) + O2

[Edited on 8-1-2013 by AndersHoveland]


I recall that the sunlight reaction should occur in direct sunlight and not diffused that is, indirect or scattered light. I have experimented with a thick glass vase (lightly sealed). In a dilute solution with diffused light and in days, the reaction to some degree could proceed as follows:

3 HOCl --uv--> 2 HCl + HClO3

so don't be too surprised by the drop in pH and accompanying increase in oxidizing strength.


[Edited on 17-1-2013 by AJKOER]

Poppy - 24-1-2013 at 15:37

Quote: Originally posted by Manifest  
I like the sulfuric acid and Calcium Chloride method.
However Poppy did you say it didn't work for you?

Take a tip. I haven't given it a try yet. Perhaps that can be a long term ticket to a hotel vacation.
Prepare a very cold, dilute solution of BaCl2. Use gloves. Carefully add a solution of 30% cold sulfuric acid until all the barium sulfate has precipitated. Let settle. Serve as will.
You can recycle Barium by ballmilling it with carbon and then calcining the resulting powder with charcoal.
BaSO4 + 2 C → BaS + 2 CO2
get rid of the sulfide:
BaS + NaOH --> Ba(OH)2 + NaS
decant then separate barium from the other ashes by fractional crystalization:
Ba(OH)2 + 2 HNO3 --> Ba(NO3)2 + 2H2O
evaporate until barium crystals appear, keep supernatant fluid for later recover.
Now you can either make nitric (not advisable) or dissolve the purified barium nitrate again, add NaOH until pH very basic, collect Ba(OH)2 and repeat the cycle.
:cool:

vmelkon - 24-1-2013 at 17:02

Quote: Originally posted by Manifest  
I like the sulfuric acid and Calcium Chloride method.
However Poppy did you say it didn't work for you?


The chemistry works. He wanted the CaSO4 to settle down so that he could decant the HCl solution. Just use vacuum filter or distill the HCl out and lead the gas into pure water.