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Author: Subject: Idea for pressurized stored HCl
palladium8
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[*] posted on 18-12-2014 at 20:40
Idea for pressurized stored HCl


A source of HCl from a cylinder would be extremely convenient. Problem is that government permits are required to purchase it in 1st world countries. HCl can be generated by any of the methods, dried, and pumped into an empty compressed gas tank with a fridge pump or the like. That's a lot of work though. So I propose this:

H2SO4 + NaCl --> HCl + NaHSO4

An empty steel* gas pressure tank with a wide enough opening to put stuff in is obtained and cleaned. The idea is to put sulfuric acid and NaCl inside and close it off. The way is to first pour the sulfuric acid. Then put the table salt inside plastic baggies loosely tied shut. Drop them carefully into the vessel, close off the tank securing it shut, and shake. Alternatively, NaCl is mixed with a little hot paraffin wax from a candle (or just vaseline) and that is dropped into the sulfuric acid. The sulfuric acid will eventually find its way to react with the salt inside, with enough agitation. This also serves to slow the runaway reaction. After shaking (or just letting it sit in a tub of water outside), you have a cylinder of like 99% HCl that can last a long time. The gas will be dry pretty much as long as the sulfuric acid is >=98% and the pressure is high. If drier HCl is needed, a CaCl2 drying tube can be improvised. Ideally with the gas tank you have a regulator that fits with a pressure gauge and a hose barb for connecting tubing.

An improvised vessel I've thought of is a fire extinguisher just cause those are so easy to rip off from stairwells. The opening in the top of one is a flare pipe thread 3/4" IIRC. So a pipe tee can be placed on top with the perpendicular end fitted on top of the fire extinguisher (a female to male adapter will be needed). One end of the tee connects to a pressure gauge that can screw in ($5 at the hardware store). The other end fits to a ball valve that then connects to a hose barb adapter to which tubing can be fitted and drawn into reaction mixtures.

Let's say we have a 2L fire extinguisher and place:
- 5 moles sulfuric acid (490g)
- 5 moles sodium chloride (290g)
giving: 5 moles hydrogen chloride (180g)

Ideal gas conditions, T=25 C, V = 2L, this builds 62 bar or 898 psi. I don't know how to calculate for the 1L of the 2L occupied by all the shit, so the total pressure is probably double that at ~120 bar. The same with 2 moles should only be 25 bar or 260 psi.

Cleaning it all up and redoing it shouldn't be hard because the bisulfite leftover is water soluble.

The only problem I see is that fire extinguishers are commonly made of aluminum. Al and aqueous hydrochloric acid is exothermic I know and generates H2. It's more than just corrosion. So I imagine high pressure HCl with aluminum where the aluminum is the bottle would be quite disastrous. Am I wrong? This is easily worked around anyway by locating one of the fire extinguishers made of steel, or better yet buying an empty oxygen cylinder (all of them are stainless steel). With a steel tank, pressurized H2 can also be made by a similar concept with Al, NaOH, and water. Put aluminum scrap in it, then NaOH in vaseline, and then water before closing it shut. That would actually be a wiser application of this set up.

I wanted to run this by the forum before I waste money on this. Any suggestions?

[Edited on 19-12-2014 by palladium8]
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Dr.Bob
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[*] posted on 19-12-2014 at 05:26


Most fire extinguishers are only rated to about 120 psi, o 898 would certainly rupture them, and the idea of an exploding can of acid seems really bad to me. HCl is much more corrosive to steel when in water than when stored as an anhydrous gas, so most metals exposed to Aq. HCl under pressure will not last long. Also, you would need a regulator of some sort to control any real pressure of HCl, and getting one that would not corrode within a short time would be tougher also, as most common acid gas ones are not designed for water to be present. If you look around, you may be able to find a lecture cylinder of HCl, but if not, I would think that building a safe on-demand HCl generator would be much safer and cheaper in the long run. Even storing HCl as the concentrated water soln, (18M) would provide a simple way to store lots safely in a glass bottle, and then just using that as your HCl source would work for many cases. And if you need anhydrous HCl, your method will not generate it either, as much of the HCl would dissolve in the water.

I have seen the results of two violent acid explosions before, they are horrifying. One was from someone mixing nitric acid waste with acetone waste and then pouring into a 1 G glass bottle and sealing it with a cap. It blew apart at night, spraying everything around the hood (of course they failed to close the sash, being a dumbass) with conc, nitric acid, which shorted out and corroded all of the electrical equipment (HPLC, etc), sprayed acid on notebooks, chemicals, and everything for 20 feet, caused the plugs nearby to short out blowing the entire circuit for the lab, ate through the water pipes, creating a water leak, and did $100,000+ worth of damage, thankfully at night, when no one was around to get killed.

The other was a post doc trying to clean glassware with some oxidant mix, who also mixed something organic with acid waste and it blew up while she was washing stuff in it, causing many injuries, burns, bleeding, and facial injuries. I did not see the immediate accident, but she was in the hospital a long time and never quite the same. Please don't pressurize strong acids or mix them with anything organic or oxidizing, unless you really know what you are doing, have the appropriate shields in place, and are wearing good PPE. I heard yet another story recently from my old fluorine chemist about a guy being killed working with fluorine and chlorine compounds that were extremely dangerous, and he was a "trained expert". How my friend Ed stayed alive while doing fluorine chemistry for 50+ years I will never know. He even used ClF3 in his days...

[Edited on 19-12-2014 by Dr.Bob]
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Praxichys
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[*] posted on 19-12-2014 at 06:07


Quote: Originally posted by palladium8  
An improvised vessel I've thought of is a fire extinguisher just cause those are so easy to rip off from stairwells.
Where I live, stealing a fire extinguisher is a third-degree felony punishable by up to five years in prison, a fine up to $5,000 or both, especially from a residential building.

And no, wet HCl will eat its way out of pretty much all common metals, even stainless steel. Carefully dried HCl can be stored in certain stainless steel alloys. Your pressure gauge and valve need to be rated to handle HCl or they will also be destroyed. I strongly advise against this. You are essentially making a giant acid bomb, and even having that thing in what I presume is an apartment building is going to get you into big trouble. Please do not do this.

By the way, the vapor pressure of HCl at 20C is 617PSI. HCl becomes a liquid at this temperature and pressure.

There are much less hazardous ways of getting dry HCl. Meth cooks make HCl generators, so there is a ton of information online about setting one up. If it is pressurized gases you are interested in, there are many others that are relatively inert and at much lower pressures that you could start with.

Look at this:

https://www.ehs.uci.edu/salerts/sep2000_lab_explosion.pdf
http://ehs.uark.edu/DocumentPages/SafetyPresentations/Compre...

[Edited on 19-12-2014 by Praxichys]




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palladium8
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[*] posted on 19-12-2014 at 12:54


Okay, well noted about the dangers of HCl. I won't do it with that. What about H2? Corrosion of steel by H2 takes ages. The steel tank will be long used/thrown out/lost before any real damage occurs. H2 actually needs to be under pressure to be useful, so it is well employed.

I'm thinking chunks of Al first thrown in, then NaOH coated in vaseline (or some other method -- have to think about this), and finally water through a funnel. My pressure vessel is rated to 585 psi = 40 bar. At V = 2L and T = 20° C, that gives us a max of ~3 moles H2 to produce. This can fill a 500mL bottle to 10 bar about 10 times, not bad. The biggest concern would be the violent runaway reaction, which could be solved by significantly slowing the rate that NaOH dissolves. If the pressure gauge spikes up too quickly (i.e., you messed up), the valve could be opened just in case. I'm gonna try this today.
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MrHomeScientist
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[*] posted on 19-12-2014 at 13:10


Trying to make your own pressure vessel is almost certainly a recipe for disaster. High pressure flammable / acidic gases in a jury-rigged container not built to withstand such things? For the safety of yourself and those around you, stay away from this.

Also stealing a fire extinguisher, as you hopefully already know, is not a good idea. Not only is this container not built for what you are trying to use it for, but what happens when there is a fire in that building and the occupants burn to death because their extinguisher has gone missing? Is that something you'd want on your conscience?


If you need gases on demand, how about this neat little piece of equipment: http://en.wikipedia.org/wiki/Kipp's_apparatus . This can be fitted with a drying tube or sulfuric acid bubbler to help remove moisture.

Recently I purchased a small cylinder of pure argon gas from my local AirGas show room - try them for some of your gas needs (probably not HCl though).

[Edited on 12-19-2014 by MrHomeScientist]
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Little_Ghost_again
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[*] posted on 19-12-2014 at 14:13


I am probably what you call a idiot risk taker, 14 and dying already..................BUT even I wouldnt try this. I am not saying you are silly or stupid but what I am saying is this is gonna end in tears.
Just not worth the risk, as pointed out exploding acid with high velocity shrapnel........R.I.P

Please dont do this, it will bite you or someone else one day for sure




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[*] posted on 19-12-2014 at 14:42


If you decide to do either of these, despite the warnings, please take a moment to write a suicide note with your SM login details, and instructions to your next-of-kin to let us know what happened.



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[*] posted on 19-12-2014 at 17:36


Breaking news: https://www.erowid.org/archive/rhodium/pdf/clandestine.hcl.g...



"You're going to be all right, kid...Everything's under control." Yossarian, to Snowden
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Little_Ghost_again
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[*] posted on 20-12-2014 at 06:39


Quote: Originally posted by S.C. Wack  
Breaking news: https://www.erowid.org/archive/rhodium/pdf/clandestine.hcl.g...


Ahhh ok in that case go ahead and try a old butane tank. I sugest a nearly empty one is best and dont forget they are easier to cut with a angle grinder if you leave some the gas in.
Big old grinder and cutting disk will get the top off for you ;)
You wont need the rewealding instructions so i wont bother posting those.
make sure you have a bucket of petrol ready in case of fire




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S.C. Wack
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[*] posted on 20-12-2014 at 11:48


Quote: Originally posted by Little_Ghost_again  
Ahhh ok in that case go ahead and try a old butane tank.


Or...keep reading...




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Little_Ghost_again
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[*] posted on 21-12-2014 at 10:13


It was tongue in cheek, but as we all have different humor I probably should point that out, and no I dont open gas containers like that!! I use the big flame torch :D




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[*] posted on 21-12-2014 at 11:18


It was a surprise to see the tanks being cut in half with a shaped charge, simply from the Cost point of view.

Surely better to blow just the Valve off, using much less explosive = cheaper.

Taking pot-shots at a round steel object seems a little crazy !




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smaerd
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[*] posted on 22-12-2014 at 10:58


I have to admit there have been times were I wish I had HCl or NH3 'on tap'. Over all though, it's been pretty rare. I've never needed more than a small glass-ware generator can provide. Storing stuff like that seems way too hazardous. I'd happily spend 2-3 minutes setting up a gas generator instead. It's your life and I won't reiterate what everyone else has already said, just don't endanger others.



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[*] posted on 24-12-2014 at 12:46


Okay tried this for making H2.

Generally I can say that as long as you're using shitty consumer grade/waste Al like chopped up soda cans, the reaction is very slow. It fizzes in the alkali solution endlessly. I did this outside where the temperature was 5 °C, so that made it even slower. There's nowhere enough juice in this to make anything "explosive" like some of you suggested. Heat would do some dramatic things, but still wouldn't blow up on you, just speed it up for the recklessly impatient. NaOH is actually regenerated in the process according to some refs, via dehydration of the NaAl(OH)4 intermediate. 3 H2O + Al --> 1.5 H2 + Al(OH)3. This made sense when I did it since even very dilute NaOH solutions (like <1M) worked.

Pretty good method. More details, maybe pics, once I finish optimizing this.
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