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Deathunter88
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[*] posted on 26-3-2015 at 02:37
Distilling Sulfuric Acid


Hello Everyone,
I have a problem obtaining sulphuric acid. Where I live (China) you need a special permit to obtain any concentration of sulphuric acid because it is listed as a precursor to "Hazardous Materials". I know that one way to get sulphuric acid is to boil off battery acid but I tried that and the sulphuric acid turned a dark brown at ~80% concentration. Because "Hardware stores" do not exist here, I cannot get the commonly used Rooto drain cleaner. However after extensive searching, I am able to obtain ComStar Hotpower sulphuric acid drain cleaner. I am planning to follow Nurd Rage's recently released video on sulphuric acid distillation. The only problem I have with it is that I will be using a 300mm Liberg condenser and I worry about it breaking due to thermal shock between the ~10 degrees C water jacket and the ~330 degree C sulphuric acid. Due to problems with my current vacuum pump I will not be able to do a vacuum distillation. How worried should I be about it breaking? I know I will always prepare for the worst case scenario but I would still like to have an idea from people who have distilled high boiling point liquids. If it is prone to breakage, then why did Nurd Rage use one?

I would also preferably use a 300mm Allihn condenser, because I use it less often and it would be less missed were it to break. Its not the problem with the cost (~5 dollars for a 300mm condenser) but more with the fact I don't like to order things individually. I would rather order glassware in large batches and I don't need anything else at the moment so I don't want to put in an order for just a condenser.
As a last choice I could use a coil condenser but its much more expensive (~15 dollars) and would be a last resort.

Video By Nurdrage: https://www.youtube.com/watch?v=tgUH0HXrOKE

Thanks for any help in advance. :)
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hissingnoise
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[*] posted on 26-3-2015 at 02:53


Quote:
I tried that and the sulphuric acid turned a dark brown at ~80% concentration.

If your battery acid contained the silicon carbide additive then the brown colour will be caused by carbon from the decomposition of the additive ─ further heating will oxidise this, CO2 will bubble out and SiO2 will precipitate.
The acid will be clear and ~ 98% . . .

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Marvin
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[*] posted on 26-3-2015 at 05:52


Silicon carbide additive? I think the sulphuric acid drain cleaners in the UK have thiourea.
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[*] posted on 26-3-2015 at 07:18


If you have the distillation apparatus setup before you turn on the heat, the thermal expansion will be slow, and it won't crack the glass.



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[*] posted on 26-3-2015 at 07:26


I have experience with distilling PBr3, which boils at nearly 200 C, which also is quite hot already. I had no issues at all. As Mol.Man. already said, the thermal expansion is slow and that also will help keeping the glass in one piece.



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[*] posted on 26-3-2015 at 08:08


As others have stated, I doubt it will be much of an issue if set up in advance with cooling, but Vogel's 3rd edition page 86 notes that for liquids with a boiling point above 140-150C, sometimes an air condenser is used. I actually have some condensers with removable jackets specifically for this purpose, though a Liebig without coolant, or a Vigreux, etc. are perfectly usable for this. This is reiterated in Techniques in Organic Chemistry by Mohrig et al. page 59 (given as 150C). I don't really think the water cooling adds much benefit in this instance, and there is a slight added expense of pumping coolant, with a slight increase in risk to your equipment, which will obviously be holding, at least in part, potentially dangerous hot acid.

[Edited on 26-3-2015 by Chemosynthesis]
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[*] posted on 26-3-2015 at 13:46


Good that you mention this. Indeed, I used simple air cooling with the distillation of the PBr3. I have a simple glass tube with suitable joints at noth ends. Above 150 C no water-cooling is required.



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[*] posted on 26-3-2015 at 14:26


I believe there is a general rule of keeping the maximum temperature difference below 150­°C, and preferably below 100°C. And as others have indicated, as the temperature difference increases the efficiency of the cooler increases. So choosing an air cooler seems like a sensible approach. if you're uncertain a combination would be a fair compromise, reducing the thermal load on the water cooler while ensuring full condensation.



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[*] posted on 26-3-2015 at 14:33


Just boil it until Fumes start coming off with H2O2 of any concentration with some stirring and it really won't matter what is in there, it will end up 98% and clear.

Edit:

Not battery acid unless you understand the chemistry of batteries, and what's in that mix at different battery charge-states.

[Edited on 26-3-2015 by aga]




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[*] posted on 31-3-2015 at 10:46


I've now watched but not listened to the NurdRage video. He makes stuff work. That's impressive, but it's not always the best way to do things and it's not necessarily safe.

Use of water cooling here isn't just risky to glassware, it's actually very dangerous. To put a worst case scenario if you had water cooling and 300+C concentrated acid then what you've made is a bomb. Adding vacuum to that could only be worse.

You've indicated you can get Quartz glassware in another thread. I suggest a Quartz flask coupled to a Quartz air condenser. The acid will pick up water from the air. Some form of receiver open to the air but protected by a moisture guard would help. (Do NOT try to seal the system completely).

Edit, I should also add that with an air condensor the acid coming over will be very hot and the receiver should at least be borosilicate, if it it's jointed glassware then it should probably quartz too to avoid problems.

[Edited on 31-3-2015 by Marvin]
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[*] posted on 31-3-2015 at 13:35


Aga, I agree that adding 12% (and maybe even more dilute) hydrogen peroxide to dirty looking, brown or pink drain opener acid and boiling does indeed clear it substantially, but in my and other's experience concentrating H<sub>2</sub>SO<sub>4</sub> to greater than approximately 95% -96% by boiling in open air at standard pressure is not easy to achieve, and even that requires that it be boiled for a while after the fuming starts.

I would imagine temperature readings would be a better gauge of when to stop, as the dense white fumes begin to appear even before ~95%. It seems to me that the acid begins to slightly decomposes and/or strongly pulls moisture from the air at these temps and concentrations, making the often stated 98% difficult to reach.

Obviously, for most purposes, that extra 2% is not an issue at all, and would likely not even be noticed unless a titration is preformed, so I guess this is nothing more than me nit-picking.

Do be safe, of course. Those fumes are quite nasty and corrosive, and it should go without saying that boiling hot, concentrated sulfuric acid is defiantly not something you want contacting your person.

[Edited on 31-3-2015 by Bot0nist]




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[*] posted on 31-3-2015 at 13:50


in fact, if you use vaccum, you can't really get 300°C

However, it's true that accident always should be considered as a serious thread and have to be keep in mind. Do never forget that any experiment can goes wrong at any time.

If you and if you want to ignore or accept the risks of a manipulation, always set your laboratory as you can quickly react to an accident and use protections.
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[*] posted on 1-4-2015 at 20:23


Quote: Originally posted by Marvin  
I've now watched but not listened to the NurdRage video. He makes stuff work. That's impressive, but it's not always the best way to do things and it's not necessarily safe.

Use of water cooling here isn't just risky to glassware, it's actually very dangerous. To put a worst case scenario if you had water cooling and 300+C concentrated acid then what you've made is a bomb. Adding vacuum to that could only be worse.

You've indicated you can get Quartz glassware in another thread. I suggest a Quartz flask coupled to a Quartz air condenser. The acid will pick up water from the air. Some form of receiver open to the air but protected by a moisture guard would help. (Do NOT try to seal the system completely).

Edit, I should also add that with an air condensor the acid coming over will be very hot and the receiver should at least be borosilicate, if it it's jointed glassware then it should probably quartz too to avoid problems.

[Edited on 31-3-2015 by Marvin]


At first I didn't quite get what you mean by "To put a worst case scenario if you had water cooling and 300+C concentrated acid then what you've made is a bomb." but after thinking about it I think I know what you mean. So the inner glass cracks and water from the jacket flows in to the inner tube. Due to the temperature change it instantly flash boils into steam. The steam pushes the remaining water back into the boiling flask and the cold water enters the 300+ degrees boiling sulphuric acid. The entire apparatus blows apart in one of those "Don't pour water into a grease fire" demos except this time it's a huge plume of sulphuric acid vapour and mist. Am I missing anything?
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[*] posted on 1-4-2015 at 20:55



Quote:

The entire apparatus blows apart in one of those "Don't pour water into a grease fire" demos except this time it's a huge plume of sulphuric acid vapour and mist. Am I missing anything?


Perhaps a few minor points such as the additional heat energy released when concentrated sulfuric acid is suddenly diluted by water- but you've for the basic idea: KABOOM! (followed by nearby personnel experiencing chemical burns, blindness, lung damage/death from pulmonary edema).

I am curious, having visited China several times. I've seen many chemicals that an amateur would have difficulty buying in USA (and even more difficulty recently in EU?) sold freely in small shops. Fireworks city (Liuyang, Hunan province) in particular, but also Changsha, Beihai and Shanghai.

You can't buy concentrated, technical grade or better sulfuric acid in your part of China?

I must also compliment you on your excellent, nearly flawless idiom and use of written English. After having dealt with many interpreters, "minders" and factory representatives, your English skills are a cut or two above most well educated mainland Chinese I have had the privilege to work with. How old are you, and where were you taught?




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[*] posted on 2-4-2015 at 00:48


Quote: Originally posted by Bert  

I am curious, having visited China several times. I've seen many chemicals that an amateur would have difficulty buying in USA (and even more difficulty recently in EU?) sold freely in small shops. Fireworks city (Liuyang, Hunan province) in particular, but also Changsha, Beihai and Shanghai.

You can't buy concentrated, technical grade or better sulfuric acid in your part of China?

I must also compliment you on your excellent, nearly flawless idiom and use of written English. After having dealt with many interpreters, "minders" and factory representatives, your English skills are a cut or two above most well educated mainland Chinese I have had the privilege to work with. How old are you, and where were you taught?

I live in Beijing so that might have had an effect on chemical purchase. All chemicals can be shipped because there is no hazmat and so almost all chemicals are available. However, there is a handful of chemicals that are on the government's list as "Precursor to hazardous material" that are very tightly controlled. Most of them are not useful to amateur chemists but is just so happens sulphuric acid is listed as one of them. Therefore it is nearly impossible to have someone ship it to you except if you have a special permit that you show the seller. Problem is, this permit is REALLY hard to get and you have to track everything you do with the chemical and they have to check your manufacturing equipment etc. Therefore, it is hard for the amateur to get sulphuric acid.

Btw, thanks for the compliment on my English skills. I am currently 13 and go to an international school. I hope someday to attend collage in America.
Cheers!
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[*] posted on 2-4-2015 at 19:04


I saw that NurdRage video sometime last week, I believe, and became very interested. I even ordered a 627 watt high temperature heat tape to make a heating mantle. Distillation does have the advantage that it not only concentrates the sulfuric acid, but also separates it from low volatility impurities such as dissolved solids. It is however a relatively hazardous process and requires large amounts of time and energy to concentrate and purify useful quantities (for my purposes at least). Most of the impurities commonly found in hardware store variety acids have not been much of a problem for me, but the concentration is normally much below 98% at about 91%. Rather than vaporizing all of the sulfuric acid the common method has been to drive off water by heating which is much less energy intensive, is relatively safe and requires less equipment. However, from what I have read it is normally considered highly inefficient to concentrate sulfuric acid to much over 95-96% max 97% H2SO4 by driving off water using heat and that is when using an absorption column to capture sulfuric acid from the rising vapor. Even if one does manage to get to 97% concentrated (close to the 98.3% azeotrope), it will quickly lose at least some concentration by pulling water from the air unless careful steps are taken to prevent this. I think I will use my new heating tape to replace the oil bath I have been using when distilling nitric acid. Not saying I will never try distilling sulfuric acid, but it doesn't seem to be the most practical solution at least for my purposes and the quantities I use.

Sulfuric acid distillation is very energy intensive. Keep in mind that the condensers ability to absorb energy should be at least as great as the energy contained in the vapor as latent heat produced by the boiler (power delivered to the boiler by the heating element minus losses). Of course working at very small scales this is not much of an issue probably.

Here are a few pdfs that provide some useful graphs and other information.

Attachment: Sulphuric Acid Concentration.pdf (159kB)
This file has been downloaded 592 times

Attachment: Aqueous Sulfuric Acid Heats of Vaporization.pdf (554kB)
This file has been downloaded 325 times

Attachment: Sulfuric Acid & Water - Liquid Vapor Equilibrium Concentration.pdf (328kB)
This file has been downloaded 271 times


[Edited on 4-4-2015 by Hennig Brand]




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[*] posted on 3-4-2015 at 14:21


Hello

Im planing to buy this distilation kit : http://www.aliexpress.com/item/500ml-24-29-Glass-Distillatio...

Also got this hob: http://archiwum.allegro.pl/oferta/kuchenka-elektryczna-inox-... 1500Watt, is this good egnouh to boil it, or do i need a heating mantle?

Thanks ;)
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[*] posted on 3-4-2015 at 19:45


Quote: Originally posted by Trizocy  
Hello

Im planing to buy this distilation kit : http://www.aliexpress.com/item/500ml-24-29-Glass-Distillatio...

Also got this hob: http://archiwum.allegro.pl/oferta/kuchenka-elektryczna-inox-... 1500Watt, is this good egnouh to boil it, or do i need a heating mantle?

Thanks ;)


The distillation set seems ok, might be a bit worried about the three way thermometer adapter, the rubber o-ring that holds the thermometer may be damaged. Also, as the temperature of the vapour is well past what the thermometer can handle, do not use the thermometer during this distillation. You might also consider getting one of the two way adapters, without the thermometer joint. If you use the liebig condenser it supplies you, do not run water through it as mentioned in the previous posts of this thread. You might consider buying an air condenser. But it's a good start.
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[*] posted on 4-4-2015 at 01:13


Thank you deadhunter88

Will try to find a adapters, without the thermometer joint :)

Quote:
If you use the liebig condenser it supplies you, do not run water through it as mentioned in the previous posts of this thread. You might consider buying an air condenser.


Hmm, why do the video on youtube use a liebig condenser?
Can u link a air condenser :)?


What about hob i have linked? Is it good egnough or do i need a heating mantle?

Thanks
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[*] posted on 4-4-2015 at 05:07


Just get an air pump and blow air through the Liebig, the same way you would with water.
Also you could just stick a glass stir rod in the thermometer's place, rather than buying a new adapter

[Edited on 4-4-2015 by Molecular Manipulations]




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[*] posted on 4-4-2015 at 05:50


Hmm,

But why Nurdrage, use water?

And do you got a link to a air pump?
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[*] posted on 4-4-2015 at 06:14


Try an aquarium air pump. Meant to run continuously.
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[*] posted on 4-4-2015 at 07:52


Thanks,
But why not water?

Also, do i need a heating mantle or will the hub work okay to boil it away?
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[*] posted on 5-4-2015 at 00:34


Quote: Originally posted by Trizocy  
Thanks,
But why not water?

Also, do i need a heating mantle or will the hub work okay to boil it away?


The inner glass cracks and water from the jacket flows in to the inner tube. Due to the temperature change it instantly flash boils into steam. The steam pushes the remaining water back into the boiling flask and the cold water enters the 300+ degrees boiling sulphuric acid. The entire apparatus blows apart in one of those "Don't pour water into a grease fire" demos except this time it's a huge plume of sulphuric acid vapour and mist. Am I missing anything?
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[*] posted on 5-4-2015 at 02:12


Quote:
The inner glass cracks and water from the jacket flows in to the inner tube. Due to the temperature change it instantly flash boils into steam. The steam pushes the remaining water back into the boiling flask and the cold water enters the 300+ degrees boiling sulphuric acid. The entire apparatus blows apart in one of those "Don't pour water into a grease fire" demos except this time it's a huge plume of sulphuric acid vapour and mist. Am I missing anything?


So it was pretty dumb for Nurdrage to make that video, without telling the risk about it ?
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