highpower48
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37% hydrochloric acid
Where is the least expensive place to buy 37% hydrochloric acid. From what I'm seeing it seems around $15.00 a pint plus shipping. Can't find locally.
Thanks
.
[Edited on 24-4-2017 by highpower48]
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JnPS
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If you have drain cleaner grade sulfuric acid and table salt you can make a simple HCl(g) generator set-up. Than simply bubble this into cold
distilled water until you have the desired concentration. Otherwise if you have muriatic acid, 31.45% HCl(aq), and sulfuric you can make an HCl(g)
generator that way and bubble it into cold distilled water until the desired concentration. Keeping the water cold to increase solubility of HCl(g)
would most likely be imperative to reach that high a concentration. I've never attempted this myself though since 31.45% is good for all my purposes
so far.
The Erowid archive has a good page on HCl(g) production:
https://erowid.org/archive/rhodium/chemistry/hclgas.argox.ht...
EDIT: Nurdrage also has a video on HCl(aq) production:
https://www.youtube.com/watch?v=YGjd7xxTuZw
[Edited on 24-4-2017 by JnPS]
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JJay
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I can buy ACS grade hydrochloric acid locally at a science supply store, but it costs almost $100 for 500 mL, so obviously I am not going to do that.
You can probably save some time by gassing the 31.45% or perhaps distilling it first and gassing the distillate.
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clearly_not_atara
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First guess would be to add CaCl2 to dilute HCl and distill. CaCl2 will absorb some water and the fractions which come over first should be more
concentrated than the mother liquor.
Gassing with HCl is possible as well but requires a more sophisticated setup.
[Edited on 24-4-2017 by clearly_not_atara]
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MrHomeScientist
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Desiccants can't be used to absorb large amounts of water in "dilute" solutions. They are only for removing the last traces of water from wet solids
or solvents. The HCl(g) generator sounds like the best bet to me. With only distilled water and HCl(g), you're guaranteed very high purity.
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Elemental Phosphorus
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You should not really attempt to distill HCl without a good gas trap and fume hood since it forms an azeotrope of about 20% with water, and distilling
a higher concentration will evolve lots of HCl fumes. Gassing with HCl is really the best option.
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j_sum1
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Are you really sure you need 37%? That stuff is right on its solubility limit and will fume like crazy. It is more standard practice to dilute your
HCl back to 30% or 25%. That minimises rusting out everything in your lab space.
If I needed 37% for a project (and I cannot imagine why), I would use conc H2SO4 and NaCl to set up a HCl(g) generator and bubble the gas slowly
through chilled HCl. I have ready access to 31% and so I would be looking to raise this by 6%. I would throw it in the freezer first to get it down
to -18C and perform the operation in an ice bath. And I would be prepared to lose more than half the HCl gas I generated -- which means both traps
and a fume hood.
But I really don't see the point. When I need a cheap strong acid, my 31% will do. And if I actually needed HCl and was avoiding water then I would
be producing some HCl gas. The gains to be made by going from 30% to 37% are greatly offset by the inconvenience.
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JJay
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37% is better for some precipitation reactions where the product is water soluble. I mainly use Klean Strip muriatic acid, which seems to be
azeotropic hydrochloric acid. I wouldn't use it to make lab lemonade, but it seems to be pretty pure.
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j_sum1
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Quote: Originally posted by JJay  | | 37% is better for some precipitation reactions where the product is water soluble. I mainly use Klean Strip muriatic acid, which seems to be
azeotropic hydrochloric acid. I wouldn't use it to make lab lemonade, but it seems to be pretty pure. |
I struggled to find a situation where this technique would even work.
I suppose precipitating KCl from a solution of KI would be one. KCl is soluble at about 28% at 0C while KI is far more soluble. This is pretty
soluble but lower than the 37% of the HCl and so it would be somewhat workable.
Still, I think bubbling HCl gas through such a solution would be more effective since negligible amounts of water would be added.
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JJay
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Certain aromatic amines are somewhat water soluble yet insoluble in organic solvents in their hydrochloride salt form. One method prescribed for
precipitating them from an organic solvent is to stir with 37% HCl.
I'm not personally working with any of these at this time; if I were, I'd probably use HCl gas.
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Si Da Sci Guy
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Try the pool shop... look for the stuff that is clear not yellow.
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j_sum1
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Sorry. This is a pretty meaningless comment.
You are right that HCl is available in pool supply shops in some locations and that it is sometimes yellow in colour, usually due to some Fe(III)
impurities.
But
(1) HCl is not easily available everywhere.
(2) The OP was asking for a route to 37%. OTC HCl is not likely to be this concentrated. (And if it is, it won't stay that way for long.)
(3) "Stuff that is clear" is not an apt description for a science forum. Not wanting to be unnecessarily nit-picky or snarky, but clear and
unambiguous communication is preferred.
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JJay
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I was going to say... if you can find 37% HCl at the pool shop, you must live in a magical Shangri-La where all the residents are chemists with
concrete floors and indoor waterslides 
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Keras
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I'm resuscitating this thread because I attempted this afternoon to concentrate 23% hydrochloric acid into 36/38% by bubbling gaseous HCl in it. At
the end, I got a liquid of density 1.192, no fumes, but a strong pungent odour of HCl gas (I guess the air was very dry today). The liquid is slightly
greenish. Is that normal?
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Pumukli
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Could you elaborate a bit more?
E.g. was your starting acid cooled during the bubbling?
Wasn't it a bit greenish/yellowish already from the beginning?
How did you generate the gas? Sulfuric acid + table salt comes to mind but you may used something else. How did you know when to stop? When the
generator exhausted?
I'm curious about the discoloration too. I have some pure 37% acid but it is in a brown bottle so can't see if it was a bit greenish.
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Keras
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| Quote: Originally posted by Pumukli | Could you elaborate a bit more?
E.g. was your starting acid cooled during the bubbling?
Wasn't it a bit greenish/yellowish already from the beginning?
How did you generate the gas? Sulfuric acid + table salt comes to mind but you may used something else. How did you know when to stop? When the
generator exhausted?
I'm curious about the discoloration too. I have some pure 37% acid but it is in a brown bottle so can't see if it was a bit greenish.
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I did use concentrated sulphuric acid dropped over table salt, and the resulting gas was bubbled though a flask containing 100ml of 23% w/w HCl I
bought at the local hardware store. The 23% HCl solution was perfectly clear.
It was fun to watch the bubbles shrink in the solution so fast they didn't reach the surface.
Maybe there was something else in the starting 23% HCl solution that made it turn greenish. Maybe the salt wasn't that pure (table salt: small
quantity of KI added, I suspect), or, more likely, the sulphuric acid, since it is 95% technical.
I'll try to take a picture if you're interested!
[Edited on 22-9-2019 by Keras]
Edit: it's more yellowish-greenish now
[Edited on 23-9-2019 by Keras]
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