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Author: Subject: Retort for sulphuric acid distillation?
ChocolateStirBar
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[*] posted on 30-10-2017 at 13:49
Retort for sulphuric acid distillation?


Hi, I'm looking for advice on how to source a retort for sulphuric acid distillation. I guess quartz would be the ideal, but the ones I found weren't quite right due to having a ground glass joint in the top of the retort.

I'm looking for a retort in which the *only* hole is the outlet of the air condenser, to cut down on sulphuric acid fumes. The fumes are entirely the reason I've not been unable to do any distillations of the acid yet. I could not do it outside either.
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LearnedAmateur
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[*] posted on 30-10-2017 at 16:12


Welcome to the forums. Simply closing off the retort with a glass stopper should do the job, there are several videos online of people manufacturing and distilling nitric acid using jointed retorts and fumes don't appear to be an issue there. You shouldn't need quartz as long as care is taken when heating, bringing the flame up to touch the glass after a minute or two, circling around the bottom to ensure even temperature.

Sorry I can't be of much help with your actual inquiry, hopefully some other members can find sources of plain retorts if that's the only way you want to go.

Also, have you considered generating SO3 gas and leading it into ice water? I'll link a procedure for the former which can be modified. This has the advantage of being conducted at a lower temperature than boiling sulphuric acid, and can further create oleum in the same flask. It must be done slowly and on a small scale though since the generation of H2SO4 is extremely exothermic - active cooling is necessary too.

http://www.sciencemadness.org/member_publications/SO3_and_ol...




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j_sum1
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[*] posted on 30-10-2017 at 16:25


I'm no expert on this one LA, but I believe it is extremely inadvisable to add SO3 to water. The better procedure is to add SO3 to concentrated sulfuric acid and then dilute that.
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Vosoryx
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[*] posted on 30-10-2017 at 17:20


I've used a ground glass distillation setup for sulfuric acid. No retort is required, and the joints leaking is not an issue so long as they are well greased and attached. Since plastic keck clips will melt off at those temp, It might be better to use metal ones, or (if you don't, like me, have any metal ones) fashion some out of copper or steel wire for the two joints before the condenser.
Retorts are cool, but seriously limited in use.

Good luck and be safe - I know it's been said before, but boiling H2SO4 is certainly not an easy walk in the park. I highly recommend boiling stones such as smashed glass or sand if you are distilling large amounts at once, and a vacuum if you have access.
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ChocolateStirBar
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[*] posted on 30-10-2017 at 20:42


Cheers for the welcome!

If I remember correctly, you grease joints with sulphuric acid itself due to the incredibly high temperatures and acidity levels involved, yes?

I also assume no-water condensing is used, or perhaps two leibigs joined together and only running water through the latter.

Whilst I do appreciate the SO3/Oleum tip, it sounds simply much too dangerous for me to even think about at the present time. I'll definitely read up on it just for the knowledge but carrying out procedures like that isn't likely due to me having to stay indoors.

Part of the reason I was gonna go with quartz was the fact that my entire setup of other glassware is chinaware, which call me paranoid but I don't know if I trust it for something as dangerous as 300c+ distillation of anything let alone H2SO4!

How do you achieve those temperatures anyway? Mantles?
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JJay
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[*] posted on 30-10-2017 at 21:57


I don't really trust borosilicate with boiling sulfuric acid either, so I use one of these for distilling sulfuric acid: https://www.ebay.com/itm/500ml-Customized-Quartz-Distilling-... I use 10,000 BTU (i.e. about 3000 watts) propane camp stove as a heat source and an ordinary borosilicate Vigreux adapter as a condenser. That seller does custom quartz labware.

It does leak a bit from the joint where it interfaces with the borosilicate condenser but it is fine in a fume hood. It doesn't seem to leak much from the top; I am quite sure that the stopper is quartz, but the stopper seems to have a slightly higher coefficient of expansion than the rest of the flask, and it grips tightly while hot. I've been meaning to have them make me a quartz condenser (something like a jointed quartz tube that I could wrap with copper tubing)....

I haven't managed to obtain sulfuric acid that is stronger than 92% from it yet, but I haven't made any special effort to keep moist air out of the apparatus.


https://www.sciencemadness.org/whisper/files.php?pid=488723&...




[Edited on 31-10-2017 by JJay]




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LearnedAmateur
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[*] posted on 31-10-2017 at 03:14


Quote: Originally posted by j_sum1  
I'm no expert on this one LA, but I believe it is extremely inadvisable to add SO3 to water. The better procedure is to add SO3 to concentrated sulfuric acid and then dilute that.


Yes, the reaction will create localised hotspots in a glass flask containing water, this is especially problematic since SO3 is a liquid at room temperature so will drip in as opposed to diffusing through the water evenly. It will probably crack the glass if the proportions are right, sometimes to the point of a small explosion.

However, if you were to bubble it into cold water in an open container that is cooled in an ice bath or with dry ice, the reaction should become far more controllable. Production of gas can also be closely varied as long as it's kept within ~10C of the decomposition temperature of the pyrosulfate.
---
I've never distilled sulphuric acid or worked with SO3 before so I can't give you any tips from experience, but yes it would be a good idea to use sulphuric acid in the joints. Temperature wouldn't be a problem for other lubricants but they will instantly char so you'd have a fun time getting the joint back out. It's probably your best bet to avoid the procedure I recommended, I'm in the same situation as you where I can't work outside and you definitely don't want corrosive vapour and flying glass indoors.

Yeah I wouldn't trust Chinese glassware much, I've bought several pieces now but they're never heated - pipettes, syringes, filters; quartz is definitely your best and safest bet, even Chinese glass will be up for the job, just make sure it's not an obscure manufacturer with an unmarked product. You'll probably need a propane torch (the ones with the bottles and screw on nozzles), camping stove is also a good suggestion, I'm not sure that there are many mantles that can go hot enough and they'll be hundreds of dollars if they can. If direct flame isn't your fancy then a sand bath should work, this can be heated from underneath and ensures even temperature distribution but will take a lot longer.




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[*] posted on 31-10-2017 at 03:25


Quote: Originally posted by JJay  

I haven't managed to obtain sulfuric acid that is stronger than 92% from it yet,[Edited on 31-10-2017 by JJay]


Oh...the stuff I was wanting to get to 96%+ is a very lurid purple 91%~ concentration drain cleaner, so I'm not sure what to do if this is the case. I can't really think of much use for heavily dyed H2SO4 that's probably 8%+ water. I'm a bit of a purity obsessive, plus it feels much nicer to have the choice to dilute azeotropic acid (carefully!) down to the required concentration.

I wonder if Ave369 (I believe that's her name) will fly into the thread and offer advice, using TFSE led me to her indoor distillation via retort thread, and the logic and results were sound.
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XeonTheMGPony
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[*] posted on 31-10-2017 at 03:36


So far I've distilled over 3L of the stuff, it can be a pain as it really likes to bump! I do 450ml batches in a 1 L flask with a hand full of crushed beaker.

Chinese glass is fine just test it first by dry heating care fully then cooling and look for any bubbles or defects.

Do not use a 3 way adapter, no point and odds are it will crack just use a 45* distilling adapter.

Get metal clips (It likes to bump and your sealed system will no longer be!)

if it is really wet run it for a while on a Vigruex column and just heat it till the dense while fums just start to appear near the top and that will help to reduce actual distill time.

Go slow and don't rush, I use a 300 mm water cooled Leibig with a water to gas exchange (Radiator) to cool it. once at a steady boil you need to tune the heat to be hard enough to keep it steady with out bumping then it will coast along to near the end befor bumping

I usually leave a 50ml tailing those get stored separated, then I use the tailings to make SO3 now for when I need very concentrated acid.

[Edited on 31-10-2017 by XeonTheMGPony]
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[*] posted on 31-10-2017 at 04:09


Quote:
Oh...the stuff I was wanting to get to 96%+ is a very lurid purple 91%~ concentration drain cleaner

Shopping around for clean acid (local hardware?) is usually worthwhile, though you'll need to check that what you're buying is water-white ─ battery acid, too, is an option, though the prolonged boiling (cough!) can be a pita...

Sulphuric acid distillation should really be a last retort:D if you can't vacuum distill.

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[*] posted on 31-10-2017 at 07:14


H2SO4 purification under vacum. Thats the key. Buy a cheap pump with 20 mbar capacity. If you have simple tap water pump and the water temperature enough cold (winter) and sufficient pipe pressure exist also good. In this case the normal borosilikate equipment is everlasting. When i was younger, destillated a lot from battery quality acid. It was really a piece of cake. Note: Between the electric pump and equipment advised a trap for acidic humidity avoid the pump. If the boiling point raises the maximum, you have in the collecting flask 97-98% concentrate of the acid. Under vacuum likewise preferable the air condenser than Liebig condenser.
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ChocolateStirBar
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[*] posted on 31-10-2017 at 16:17


Good advice, thanks guys.

I haven't looked too hard, but OTC sulfuric acid isn't that easy to get here, hence why I went with the purple stuff.

As a less than subtle hint, the government seemingly does not like nitric acid, nor peroxides, nor perchlorates (admittedly I have absolutely 0 use for the latter, EM aren't an interest of mine).

The fact those chemicals are banned, even for uses as benign as producing silver nitrate or piranha fluid, makes me think perhaps H2SO4 will go the way of the dodo as well soon.
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[*] posted on 31-10-2017 at 17:06


Depends on the country, but yes. I know one store where I can find the H2SO4 drain cleaner where I live, but I know that other people have trouble depending. When I did find the one store, I bought a crap ton just in case they stop carrying it.

Finding cheap nitrate salts for making HNO3 is also a PITA. Using the Potassium Nitrate that CAN be found in SOME stump removers makes most a little sticker shocked. Ammonium Nitrate in cold packs is hard to find nowadays. I work for a company that has a license to buy NaNO3 as an industrial fertilizer, and I bought a 50 lb bag through their license.

With the overpricing and limited availability of some of the most commonly required things for amateur chem, I wouldn't be at all surprised to see easy Sulphuric acid vanish in the years coming...
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