Sciencemadness Discussion Board - Purifying/increasing % HCl in Hardware store Acid

Purifying/increasing % HCl in Hardware store Acid

Actinium - 11-1-2015 at 11:43

I was just wondering if it was better to just gas the HCl to saturation to get the 37% or make it from scratch?
Assuming that one would want to not purchase it?
JUst curious

vmelkon - 11-1-2015 at 13:47

Some look a little green presumably due to Fe(2+). Some of them are clear.

If your store sells dirty stuff, then go ahead with the old NaHSO4 + NaCl and lead the HCl into fresh water.

HgDinis25 - 11-1-2015 at 14:02

It's a matter of price. Most hardware HCl is dirt cheap but either has some contamination in it or isn't concentrated enough. In my case, just buying the HCl is much more rentable than making it from Sulfuric Acid and Chloride salts.

If you can buy 33/37% HCl but it has impurities in it, simple distillation should remove them and leave you with fairly pure Hydrochloric Acid.
On the other hand, if your store only sells diluted stuff, you may want to concentrate it. HCl and water form an azeotrope that boils at 110ºC and leaves you with 20% concentrated stuff. If you need more concentration, adding Sulfuric Acid and bubbling the resultant HCl gas may be an option...

Actinium - 12-1-2015 at 09:56

Quote: Originally posted by HgDinis25

It's a matter of price. Most hardware HCl is dirt cheap but either has some contamination in it or isn't concentrated enough. In my case, just buying the HCl is much more rentable than making it from Sulfuric Acid and Chloride salts.

If you can buy 33/37% HCl but it has impurities in it, simple distillation should remove them and leave you with fairly pure Hydrochloric Acid.
On the other hand, if your store only sells diluted stuff, you may want to concentrate it. HCl and water form an azeotrope that boils at 110ºC and leaves you with 20% concentrated stuff. If you need more concentration, adding Sulfuric Acid and bubbling the resultant HCl gas may be an option...

Just so I understand correctly, if its contaminated and I want to distill it, and say it's 31.45% HCl, will it come over at 110 C. 20% because of the azeotrope? Then would have to re concentrate it?
Also would it be advisable to dilute it first prior to distillation or can it be done as such from the bottle? I'm just starting to work with acids and such. thank you for your replies and patience.
-AC-

[Edited on 12-1-2015 by Actinium]

careysub - 12-1-2015 at 11:15

Quote: Originally posted by Actinium

...
Just so I understand correctly, if its contaminated and I want to distill it, and say it's 31.45% HCl, will it come over at 110 C. 20% because of the azeotrope? Then would have to re concentrate it?
Also would it be advisable to dilute it first prior to distillation or can it be done as such from the bottle?

Since ~31% is above the azeotropic concentration the initial distillate will be more concentrated in HCl than your original solution, in fact I think it will simply distill pure HCl gas (not sure about this though - I've certainly never done it).

If your only concern is too increase the strength of the acid, use the 31% HCl in your collecting flask also to bubble the HCl through it. Discontinue when the 20% azeotrope is reached, and it starts coming over.

If you are also trying to purify the acid of any salts then collect the HCl gas in distilled water, switch flasks and bring the azeotrope over, you will end up with pure 20% HCl, with any dissolved salts left behind.

You can then use that for collecting HCl gas in a second distillation.

metalresearcher - 12-1-2015 at 13:37

Strange. Azeotropic HCl acid is 20% and concentrated is 37%. I thought this is the same concentration. What explains this difference and how does industry make 37% acid ?

gdflp - 12-1-2015 at 13:43

Concentrated hydrochloric acid is made by gassing either water or azeotropic hydrochloric acid with hydrogen chloride to the point of saturation.

vmelkon - 13-1-2015 at 07:18

Quote: Originally posted by careysub

That is correct. The vapor pressure for HCl is low, so it will gas off first and concentration of your liquid in the RBF will go down to the point of azeotrope.

The same thing happens with ethanol water mixture. If you are above the 89% mol point (or above 95% by weight), the vapor will be high concentration ethanol. The liquid in the RBF will go down to 89% mol (95% weight).

But I suspect that it can be more complicated than. It is highly depending on the bp various ethanol + water combinations.

[Edited on 13-1-2015 by vmelkon]

Actinium - 14-1-2015 at 11:36

so since the pressure on HCl is low and will fume off, what would be the ideal and safe way to distill this to use whatever is gassing off first to saturate dH20 until I get to the azeotrope of 20% ?
Or is it one of those things where the HCl is going to come off and just wait for the 20% solution to come over and use that as feed stock for either saturation of dH2O or saturation of the 20% solution it's self?

I had found a post that I can ;longer find and I know Woelen had made a few comments about such as well as saying that the residual solution is great for cleaning glassware.

Praxichys - 14-1-2015 at 11:59

If you start with 31.45% and boil it, HCl(g) and a small amount of water will be given off until the solution reaches 20%, at which point the rest will distill over at 20%.

If you start with less than 20%, mostly water with a little HCl will be given off until the solution reaches 20%, at which point the rest will distill over at 20%.

If you want to re-saturate your distilled 20% HCl, boil the 31.45% and use the vapors to gas the clean, pre-distilled stuff back up to saturation, which will simultaneously reduce the dirty 31.45% down to the 20% azeotrope. You can then finish distilling the dirty stuff to another container to make more clean 20%, and the process repeats itself.

You can purify without distilling by placing an open container of the HCl in a sealed bag with another open container of dH2O. The HCl will equalize concentration in both solutions after a few days, depending on the temperature. To calculate the final concentration, simply treat it as if you were adding the water to the HCl.

To gas HCl into a solution efficiently, keep the solution as cold as possible, keep the gas bubbles as small as possible, and keep the bubbles in contact with the solution as long as possible. It is ideal to use a tall, narrow container and introduce gas through a long straw to the bottom of the vessel. The straw is shaped to blow the tiniest bubbles possible. Be careful with suckback.

[Edited on 14-1-2015 by Praxichys]

MrHomeScientist - 14-1-2015 at 13:06

The name for the contraption Praxichys mentions, by the way, is a gas wash bottle.

I have one of these, but every single time I use it suckback is almost instantaneous when the gas flow starts. I've never been able to use this thing properly. Anyone have any tips?

If, like me, you are plagued with suckback, the 'inverted funnel trick' works great:

If suckback starts, the water level outside the funnel lowers enough to break the seal and stop it from flowing further up the gas line.

Loptr - 14-1-2015 at 14:24

Is there a better method to handle the suck back than to have a suck back flask in between the gas generator and the flask with the dispersion tube?

Is there something that handles this situation a little more elegantly? I know about one-way valves, etc., but is there cheap chemical resistant solution for instances like this that cut off when it starts to flow the other way?

[Edited on 14-1-2015 by Loptr]

Darkstar - 14-1-2015 at 19:12

Quote: Originally posted by Actinium

I was just wondering if it was better to just gas the HCl to saturation to get the 37% or make it from scratch?

Considering how cheap hardware store HCl is, I'd just make it from that. Why waste valuable sulfuric acid or even NaHSO4 when you can literally get a gallon of 31.45% HCl for a few dollars? (assuming you can in your area since you mentioned it) Even if it's too impure for what ever it is you need it for, it's still a great source of cheap HCl gas.

As others have pointed out, heating some 31.45% HCl will produce HCl gas. However, a better method--in my opinion, at least--for generating cheap HCl gas from an aqueous solution is to simply dehydrate it using anhydrous CaCl2. Just drip the acid over some dry CaCl2 in a gas generator and you'll get plenty of gas. This can be done with or without heat. Depending on how efficient you want to be, the resulting solution of CaCl2 and HCl can also be distilled, and your anhydrous CaCl2 can be regenerated by heating it in the oven at 200°C for a couple of hours. (hardly worth the effort, though, considering how dirt cheap both CaCl2 and HCl are)

If purity isn't an issue, slowly bubble your HCl gas into a cooled solution of the store-bought acid until it's saturated. If purity is what you're after, distill over some pure 20% HCl first and then gas it. That, or use dH2O.

[Edited on 15-1-2015 by Darkstar]

gdflp - 14-1-2015 at 19:16

@Loptr

Look at MrHomeScientist's post above you. That's what I use and it works wonders, the only problem is it uses a three prong clamp and ring stand. All that is needed is a funnel and a beaker.

Actinium - 14-1-2015 at 23:21

thank you guys. that was really helpfull and learned alot and cant wait to give it a go. as far as safety goes, i can read msds and wiki ect.. all day but i would like some personal tricks or things that you would only pickup on the job? are there certain materials I shouldn't use? should silicon be used on the joints or is it like distilling chloroform where it disolves the grease into your product?

Zombie - 16-1-2015 at 09:53

I've googled around for that answer, and I found several PDF's on compatibility of "Cured Silicone" or silicone "O" rings or Silicone diaphragms...
All of them indicate that Silicone (in those forms) is NOT compatible w/ HCL.

I found one post on Erowid that stated you MUST use silicone grease on joins when using HCL.

That being said I am every bit as curious as you are to here a definitive answer from several posters.
I understand set or cured silicone is different from the grease form but I would like to know how or in what way.

That is an excellent question Antinium. One I would have not thought to ask.

Praxichys - 16-1-2015 at 11:02

Grease is recommended when distilling HCl since the escaping vapors can be irritating, damage polyacetal keck clips, and corrosive to anything metal in the vicinity like rings, clamps, rods, stands.

Silicone oil is not the most inert substance around to be using in glass joints. A perfluorinated hydrocarbon grease is preferred, often sold as "high vacuum grease" which I have found to be inert and insoluble in aqueous acids, and should be fine for your application.

You can run the distillation without grease, but be prepared to ventilate a small amount of HCl vapors that will undoubtedly escape. Use your oil not on the joints, but instead to coat the rods and stands with a thin film to prevent attack by HCl. Adequate ventilation is a must.

To avoid grease contamination with chloroform, use only a very tiny amount of grease, or do not grease any joints beyond the still head and instead allow the distilling liquid to penetrate and seal the joint. Some leakage will occur in the latter method; it is really a matter of choice whether this presents a problem, depending on the adequacy of your ventilation.

Zombie - 16-1-2015 at 12:46

Very helpful. I copy/pasted this from one manufacturer... About 40.00 USD for 5 oz. I imagine that is 1/2 a lifetime worth if used correctly.

http://www.2spi.com/catalog/vac/y-vac.shtml

Fomblin® VAC™ 3 is a perfluoropolymer based vacuum grease thickened with a PTFE thickener. It is an inert, homogeneous, and white grease particularly suitable for use as a lubricant for mechanical parts or seals operating at high vacuum and in contact with aggressive chemicals or oxygen. VAC 3 is used in lubricated "for life" applications; its lubricating properties make it suitable for parts requiring boundary (extreme pressure) lubrication in a temperature range from -20°C to 250°C. VAC 3 is designed to meet MIL-G-27617 Type III specifications and test method ASTM E-595-77 as tested by NASA/GSFC (extremely low outgassing in a vacuum environment). Before making any decision about your vacuum grease requirements, be sure to be aware of some of the other information and specifications concerning VAC 3 high vacuum grease.

gdflp - 16-1-2015 at 12:50

Yeah, perfluorinated grease is rather expensive, but a tube that big will last for many years. I haven't invested in one yet, but I've ruined a multitude of Keck clips in the past few months so I probably should.

macckone - 16-1-2015 at 13:53

United glass tech sells ptfe sleeves for ground glass joints.
Plumbers pfte tape also works well.

Zombie - 16-1-2015 at 14:26

I've seen those rings, and read about the PTFE tape method.
Both are less expensive but IMHO they could be more problematic in the long run. I'm a K.I.S.S. kinda guy

Actinium - 17-1-2015 at 12:29

that being said, I really need to invest in building a Fume hood, and getting some More protective gear for my face ect... I imagine is a must..
I'll get to it and report my results.

And will vinyl tubing work or do we need something steadier?

Zombie - 17-1-2015 at 15:03

For supporting a fume hood? (vinyl tubing)

I'd think more like threaded rod, and covered w/ vinyl shrink tubing. Just one approach.

I mounted mine under a shelf, and vented it straight out the back thru the outside wall.

Sniffity - 18-1-2015 at 20:32

The Home Scientist (Robert Bruce Thompson) has a fairly simple method for purifying OTC HCl: https://www.youtube.com/watch?v=jv1Ms6Subg4

Question for everyone, though: Is there any way to confirm that hardware store HCl has impurities dissolved in it? What sort of impurities are we likely to find in hardware store HCl, and why?

Zombie - 18-1-2015 at 20:59

I copy/pasted this...
" Pure grades of hydrochloric acid are colorless, but technical grades, commonly called muriatic acid, are often yellow-colored because of impurities such as dissolved metals. Most hydrochloric acid produced has a concentration of 30% to 35% hydrogen chloride by weight."

The entire article is here...
http://encyclopedia2.thefreedictionary.com/Anhydrous+hydroch...

Although it does not detail the exact "metals"/salts, it does give enough info to know what you are using.

I linked the same vid as you in another thread, and was assured that is a good method for purifying store bought Muriatic acid, and there is some information for concentrating the resulting "reagent grade HCL. Here is that thread... http://www.sciencemadness.org/talk/viewthread.php?tid=17638&...

Darkstar - 18-1-2015 at 22:20

Quote: Originally posted by Sniffity

Is there any way to confirm that hardware store HCl has impurities dissolved in it? What sort of impurities are we likely to find in hardware store HCl, and why?

Hardware store HCl will just about always be impure due to the nature of its production, and will generally appear slightly yellow in color. The color is most likely due to aqueous iron salts and free chlorine, and possibly some organic compounds. Other possible impurities are sulfuric acid, nitric acid, and chloride salts of sodium, calcium and lead. Really just depends on how it was produced.

UncleJoe1985 - 2-2-2015 at 14:08

I'd like some pure HCl(aq) for neutralizing a chlorate cell. Although the simple method presented by Robert Thompson is perfectly adequate, I'd like to consider alternatives for getting it above 20% to reduce storage space.

I've thought of 2 ways by controlling temperature and pressure.

1. Just distill HCl from A to B under high pressure.

2.
a. connect 3 glass vessels A, B, C. Fill A with impure HCl (aq). Fill B with water.
b. quickly create a vacuum and heat the contents of A. This should cause the dissolved HCl to start evaporating. Not much will dissolve in B due to the low pressure.
c. Without disturbing any seals, pour the now relatively depleted acid in A into C. Then close off the valve between A and C. This should still leave almost all the gaseous HCl in A & B.
e. Now pump in air from the outside to reduce the partial pressure of HCl, causing it to dissolve in B.

#1 should be simple, but would it be too slow since the high pressure will tend to keep HCl in solution? Also, what pressure do I need to get say 30%?

Is #2 worth pursuing? My question is how much HCl can I cause to come out of solution using low pressure and high temperature? It seems if I can make > 80% of the original 30% come out, then it would be worth it.

[Edited on 2-2-2015 by UncleJoe1985]

blogfast25 - 2-2-2015 at 14:40

Quote: Originally posted by UncleJoe1985

I'd like some pure HCl(aq) for neutralizing a chlorate cell. Although the simple method presented by Robert Thompson is perfectly adequate, I'd like to consider alternatives for getting it above 20% to reduce storage space.

It's nice of you to include a reference but 'Robert Thompson' won't mean that much to most here (myself included).

To reduce storage space? Blimey, just how much HCl solution are you planning to store?

Quote: Originally posted by UncleJoe1985

b. quickly create a vacuum and heat the contents of A. This should cause the dissolved HCl to start evaporating.

And the contents of A to start boiling, of course. At the top of Mount Everest water boils at 70 C.

I believe to prepare HCl > 20 % dissolving a known amount of pure HCl gas in the required amount of water is the only practical way.

[Edited on 2-2-2015 by blogfast25]

Zombie - 2-2-2015 at 14:41

Looking at the WIKI page for HCL (http://en.wikipedia.org/wiki/Hydrochloric_acid) there is a boiling point chart that indicates BP's lower than that of water.
I may be wrong so correction may be needed but I believe that a fractional distillation rig can be used targeting specific temps bellow 100* C at atmospheric pressures.

As you stated heating, and collecting the vapor should be the same as the room temp vapor transfer method . I can see that saving some time.

blogfast25 - 2-2-2015 at 14:52

Quote: Originally posted by Zombie

I may be wrong so correction may be needed but I believe that a fractional distillation rig can be used targeting specific temps bellow 100* C at atmospheric pressures.

You're aware of the (approx.) 20 w% HCl/water azeotrope, right?

Zombie - 2-2-2015 at 15:04

Yes sir. There is a point of diminishing return I believe it is 35-37% concentration. I am simply looking at the purity aspect more than the concentration.

UncleLoe is asking from a starting point of 20%, and I assume OTC purity. I don't think much "storage space will be gained but "pure" was my focus.

The Thompson vid. (method) is linked on page one of this thread.

[Edited on 2-2-2015 by Zombie]

gdflp - 2-2-2015 at 15:17

Quote: Originally posted by blogfast25

It's nice of you to include a reference but 'Robert Thompson' won't mean that much to most here (myself included).

I believe that he is referring to this video.

blogfast25 - 2-2-2015 at 15:55

Quote: Originally posted by Zombie

Yes sir. There is a point of diminishing return I believe it is 35-37% concentration.

The Thompson vid. (method) is linked on page one of this thread.

Now what did I tell you about expressing yourself concisely?

At STP, 35 w% (approx.) is simply the solubility limit of HCl in water. No need for flowery language.

Thanks for the link reminder (washing egg off face now).

[Edited on 2-2-2015 by blogfast25]

Zombie - 2-2-2015 at 17:06

Standard conditions for temperature, and pressure. Got it
Thanks!

UncleJoe1985 - 3-2-2015 at 06:51

Nevermind about thinking it can save space. It was just a familiar feeling since here in the San Francisco bay area, space is kind of at a premium. For neutralizing a chlorate cell, I only need small, but pure amounts of HCl. For making NH4ClO4, I would need a lot of HCl and NH3 (hopefully neither needs to be pure).

Quote:

a fractional distillation rig can be used

Have you done this? because I doubt it. I found this phase diagram,

but I don't think it can be used much since something being distilled isn't a system in equilibrium.

But intuitively, the initial vapor will be very high in HCl, probably over 45% by weight. At that percentage, no amount of chilling is going to make it a liquid. It's all going to escape into the air.

Even if the HCl in the vapor is lower at say 33% and 80C, after chilling it to 20C,

gas weight(both HCl and H2O) = 47%, HCl in gas weight = 47% * 42% = 20%
liquid weight = 53%, HCl in liquid weight = 53% * 25% = 13%

25% HCl is pretty good, but overall that's only capturing 13% / 33% = 39% of the HCl from the initial hot vapor.

Quote:

collecting the vapor should be the same as the room temp vapor transfer method . I can see that saving some time

No, my main purpose isn't to save time. It's to create a concentration significantly larger than the 15% the room temperature method achieves.

I'm still don't have a chart for how pressure can increase the % of dissolved HCl.

I also find it puzzling that according to the chart, for 31% HCl to be at equilibrium at 20C, 35% of the mass would have to be vapor! For a 1 gallon jug that would be 860 liters of vapor (at STP)! Clearly, that won't fit inside that jug. That would explain why when I unscrew the cap, I hear a fizz and why the air stinks up so fast.

So clearly, the 31% HCl isn't at equilibrium. How did it get so strong? Was it due to massive pressurization during manufacture?

[Edited on 3-2-2015 by UncleJoe1985]

[Edited on 3-2-2015 by UncleJoe1985]

Zombie - 3-2-2015 at 17:25

Quote:

"I may be wrong so correction may be needed but I believe that a fractional distillation rig can be used targeting specific temps bellow 100* C at atmospheric pressures."

That was the entire statement.
No I have not attempted to distill Hydrocloric Acid to concentrate it. I did however ask on another thread about evaporating same, and was informed that evaporation can be achieved to reach the STP 20% concentration. Again however the point of diminishing return...
http://www.sciencemadness.org/talk/viewthread.php?tid=17638
(2nd page near the end of the thread)

The only other option I can think of would be to bubble Hydrogen Chloride gas thru your existing HCL to the point of saturation.

I'm obviously still learning, and attempting to help or stimulate ideas where I can.

[Edited on 4-2-2015 by Zombie]

mysteriusbhoice - 22-6-2020 at 07:00

I only see this dirtied 36% acid with cloudy soaps to prevent its use as a reagent but I had found a solution.
by adding tiny amounts of alum no more than a pinch help precipitate that cloudy polymer no distillation required.
however the acid will have a tiny amount of alum the amount used is really small but theres no other way than distilling to get it at higher concentration.

Refinery - 22-6-2020 at 08:36

Never have I ever used any grease on glass joints and had zero issues. Aspirator vacuum pump holds vacuum for a long after I've stopped it. I never store anything with joints attached though, to avoid jamming. I had once almost a breakdown with one joint this way, and have scrupulously keeping them apart since.

Teflon sheets 0.5-1mm thick and plumbers tape are excellent sealants for any non-glass joints. I have a couple of flange joints on SS equipment and I've made teflon gaskets that work like a charm.

Frankenshtein - 19-9-2020 at 06:41

I came here to post the Robert Thompson video but I see that I'm too late.

draculic acid69 - 23-10-2020 at 16:49

Quote: Originally posted by HgDinis25

Distillation is a crappy idea.an hr or more of boiling acid sounds terrible.everyrhing U use around it will probably rust. To concentrate or purify just put some hcl in a coke bottle drop in some calcium chloride or Al foil and lead fumes thru half as much clean water as hcl used.instant conc clean hcl.al foil is better and quicker than damprid.
Over and done with in a few minutes.no need to distill.the HCl goes from one bottle to the other so easily

draculic acid69 - 23-10-2020 at 16:51

Quote: Originally posted by mysteriusbhoice

I only see this dirtied 36% acid with cloudy soaps to prevent its use as a reagent but I had found a solution.
by adding tiny amounts of alum no more than a pinch help precipitate that cloudy polymer no distillation required.
however the acid will have a tiny amount of alum the amount used is really small but theres no other way than distilling to get it at higher concentration.

Drop a big piece of Al foil and lead fumes thru distilled water.easy.

symboom - 23-10-2020 at 22:35

However, it is possible to purify crude hydrochloric acid for other purposes using the two-container technique.

http://www.sciencemadness.org/smwiki/index.php/Hydrochloric_...

I'm glad to see that this was added to the wiki

This is the only video on it
https://m.youtube.com/watch?v=jv1Ms6Subg4

The process takes a week or two to finish, and the resulting reagent-grade acid is about 5 molar rather than the 12 molar typical of commercial concentrated hydrochloric acid. Still, it's extremely pure and concentrated enough for most purposes.

if it was in a reduced pressure environment (small vaccum);it would speed the process along faster

[Edited on 24-10-2020 by symboom]

[Edited on 24-10-2020 by symboom]

Fyndium - 24-10-2020 at 00:14

How much did the hw store HCl cost?

It determines a bit how much of an option it is to do it yourself from scratch.

If sodium bisulfate or sulfuric acid is available for cheap, then probably it is. Hydrochloric acid and hydrogen peroxide are two products that command an exceedingly high price per mol of reagent for consumer market. For example, I had otc 3% H2O2 available for 12€ per liter, which translates to same per mol. 35% costs the same, it just needs one trick to buy it, being almost 12 times cheaper per mol.

Here, pool stores sell 35% HCl in canisters. They are cheap, like 20-30eur per can of 30 liters, but the shipping quickly becomes an issue and doubles the price.

You could check how much it would cost to use calcium chloride to desiccate the HCl and dissolve the gas in new solvent?

symboom - 24-10-2020 at 00:24

Small amounts of hydrogen chloride for laboratory use can be generated in an HCl generator by dehydrating hydrochloric acid with either sulfuric acid or anhydrous calcium chloride.

That's use full so if you add solid calcium chloride it will push the hydrogen chloride out of solution in a closed system in into another container with distilled water.
Thats a great improvement than just waiting a week

_____
This reminds me of concentrating nitric acid procedure with
Magnesium nitrate

The principal use is as a dehydrating agent in the preparation of concentrated nitric acid

[Edited on 24-10-2020 by symboom]

artemov - 24-10-2020 at 06:51

Where I am, 8.5% HCl in tile cleaner cost $1 per litre.

I just boil half a portion away (mostly water) to get to 15-16%, then add 10% by weight of anhydrous CaCl2 and do a simple distillation.
I managed to get a clean clear 24-25% HCl (by density).

I supposed you can get a higher concentration by adding 20% or 25% CaCl2, but I don't need a higher concentration nor want to store one.

[Edited on 24-10-2020 by artemov]