Sciencemadness Discussion Board - Distilling Sulfuric Acid

Distilling Sulfuric Acid

Deathunter88 - 26-3-2015 at 02:37

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.

hissingnoise - 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% . . .

Marvin - 26-3-2015 at 05:52

Silicon carbide additive? I think the sulphuric acid drain cleaners in the UK have thiourea.

Molecular Manipulations - 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.

woelen - 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.

Chemosynthesis - 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]

woelen - 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.

Fulmen - 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.

aga - 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]

Marvin - 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]

Bot0nist - 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]

brubei - 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.

Deathunter88 - 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?

Bert - 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?

Deathunter88 - 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!

Hennig Brand - 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 1183 times

Attachment: Aqueous Sulfuric Acid Heats of Vaporization.pdf (554kB)
This file has been downloaded 748 times

Attachment: Sulfuric Acid & Water - Liquid Vapor Equilibrium Concentration.pdf (328kB)
This file has been downloaded 713 times

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

Trizocy - 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

Deathunter88 - 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.

Trizocy - 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

Molecular Manipulations - 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]

Trizocy - 4-4-2015 at 05:50

Hmm,

But why Nurdrage, use water?

And do you got a link to a air pump?

hyfalcon - 4-4-2015 at 06:14

Try an aquarium air pump. Meant to run continuously.

Trizocy - 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?

Deathunter88 - 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?

Trizocy - 5-4-2015 at 02:12

Quote:

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

homealchemy1 - 5-4-2015 at 02:45

Quote: Originally posted by Deathunter88

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?

Are you basing this on your personal experience or theorizing it? Nurdrage is a veteran not an amateur. I hate when someone pontificate from the ivory tower. Deathunder88 -- have you tried this distillation using your own method?

The fact is that you must first run the water and as the temp. of the vapor is ramp up gradually, it will condense. that's why its absolutely important that you run the condenser first with water and slowly increase the temperature of the mantle.

I've tried it on a small scale and its fine. You must not rush this distillation!!! Don't use the three way adapter, use the 75 degree bent adapter just like Nurdrage did. It took me 5 hrs to do everything and clean up and I got 100ml of clean acid.

[Edited on 5-4-2015 by homealchemy1]

Deathunter88 - 5-4-2015 at 03:05

Quote: Originally posted by homealchemy1

Quote: Originally posted by Deathunter88

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?

It is speculation, but I don't want to find out if it will actually happen. Besides, its good practice to use an air condenser for any liquid that boils above 150 degrees C.

Trizocy - 5-4-2015 at 06:58

Quote:

Thanks, but is the hub good enough or do i need to order a heating mantle?

Magpie - 5-4-2015 at 07:51

I can buy Rooto 96-98% H2SO4 so don't have to suffer the indignity of distilling this dangerous reagent.

Instead of plugging the stillhead with a thermometer adapter use a glass plug. If you can get a tapered glass thermometer insert that would be ideal. How necessary is temperature indication to this process?

I would definitely avoid using water as coolant - using forced air or nothing sounds like the way to go.

A good quality borosilicate West or Liebig condenser should handle temperature differences well. I have distilled 200°C bp liquids many times with ice water (don't ask me why the ice - habit, I guess) in my West condenser with no problems.

[Edited on 5-4-2015 by Magpie]

Fulmen - 5-4-2015 at 08:02

I think it's pretty much common sense not using water at these temperatures, especially with stuff like strong acids.
As for the setup wouldn't a column be required for concentrating without too much loss? If so I'd consider using the cooler as an insulated column and using something like a vigeraux for cooling. The reflux could then be adjusted with airflow through the cooling jacket. Or am I missing something?

Trizocy - 5-4-2015 at 09:22

Quote:

I can buy Rooto 96-98% H2SO4 so don't have to suffer the indignity of distilling this dangerous reagent.

Nice for you, but for me i cant import it to my country, really strict when it comes to concentrate sulpuric acid, its on: "watch over list"

Only thing i can get is drain cleaner with 50%-90%, so the only way i can get it concenrated is distiling it.

May someone share a video on youtube, where they use air as coolant at the condenser and not water? Only finding water coolant :/

Trizocy - 5-4-2015 at 09:54

Was wondering how concentrate can i get the sulpuric acid if i just use a beaker and hub?

Sulfuric Acid

DSC_JN - 5-4-2015 at 14:06

You might be able to obtain 96% Sulfuric acid by contacting agricultural suppliers, 96% is often used to balance the pH of animal manure. Often it is possible to obtain a permission/dispensation from the rules depending on usage.

Does anyone here have any suggestions on how to recover and seperate sulfuric acid and nitric acid waste from nitric acid distillation to around 99+%? Keep in mind that the waste might contain some remains of nitric acid and will have a sulfuric acid concentration of around 70%.

Jeppe Nielsen, Danish Space Challenge (DSC)

EDIT: Our current procedure for waste handling is just to use the slightly diluted acid to neutralize animal manure; a process were any remains of the nitric acid will improve the manure as a fertilizer.

[Edited on 5-4-2015 by DSC_JN]

radiance88 - 5-4-2015 at 16:15

Guys OP here is 13 years old. I highly doubt having him run through the bureaucratic mill is going to get him the acid that he needs. He definitely needs to distill/clean it himself.

Btw kudos OP. You've got great English and it's always nice to have members from such distant and unexpected places.

DSC_JN - 5-4-2015 at 17:00

Unfortunately it's nearly impossible to legally obtain small quantities of certain chemicals (kg or liters), but when you try ordering in bulk (tons or cubic meters) then it becomes easy to obtain chemicals which are otherwise more or less impossible to get.

Personal experience:
Getting 100-200kg of 99+% Nitric Acid is impossible, but ordering 28 tons is easy. We ended up having to distill 53% nitric acid to 99+% by mixing it with sulfuric acid (96%) in order to bind the water. That's why I suggested agricultural suppliers, as we had luck obtaining 53% nitric acid and 96% sulfuric acid from them in bulk scales.

Point of the story, even with legalities in order it's near impossible to obtain small amounts of restricted chemicals, at least at reasonable prices. If you can, order bulk amounts.

Jeppe Nielsen, DSC

byko3y - 7-4-2015 at 06:54

Wonna tell you something from my experience of H2SO4 distillation.
One of the problems is already discussed here - you can't cool the condenser with water. The other problem I had - leaking acid through the horizontal socket between stillhead and condenser above 290 C.
At the picture you can see a good example of setup you can NOT use for distilling sulfuric acid above 85%.

-font-b-Glass-b-font-font-b-Distillation-b-font-font-b-Apparatus-b-font.jpg - 108kB

Probably if you turn your stillhead 45 degrees so all your sockets will be at least partially vertical - you might be able to avoid horrible acid smoke. It works better for 60-75 degrees angle on your three-way adapter. (remember, that you cannot use water in the first condenser)

You need a setup with all sockets vertical on the hot side and preferable air cooled, like this one.

24-40-Glass-3-Way-Adapter-Oblique-Down-Type-Parallel-Joints-Distillation-Adapter.jpg - 23kB

and a water-cooled vertical condencer to cool the hot liquid acid coming from the adapter, like in this setup

This way I made 90% concentration and at least 99% pure sulfuric acid that was as clear as distilled water. Would be glad to show you photos of my setup, but they are bad and won't show you much.
I've never encountered any large amount of water leaking into the hot concentrated sulfuric acid, but I've seen one drop of water falling into the boiling acid - it made a little explosion. I would not dare to allow any appreciable amount of water to be anywhere near the hot acid.
Once I had a cold acid sucked back into the hot part. It went pretty safe and the distillation ended immediately, but - I've got a stillhead and condenser destroyed.
The same reason why you should absorb SO3 with sulfuric acid and not with water - because water explosively turns into steam on contact.

Trizocy - 19-4-2015 at 14:29

Hmm, thanks bykno3y.

I have got a setup like nurdrage now, so gonna try to distill some sulp acid soon.
Got a water pump laying around here, but are skeptical to use it, since most here dont recommend it. Still strange that nurdrage use water with the condenser like it was no problem.

byko3y - 19-4-2015 at 16:09

I doubt that nurdrage got 98% H2SO4. First, because it lays in the last 20-30% of sulfuric acid. And second, because he uses open receiving flask, and 90%+ sulfuric acid readily absorbs moisture from air.
Also, I forgot to mention that you need a porcelain boiling stones, preferably ones that were already treated with conc sulfuric acid (otherwise some crap the stones them will come into our acid). I made my from a broken porcelain cup. Porcelain brick also seems to work well.

Mesa - 19-4-2015 at 18:44

Lots of the posts here are drastically underestimating borosilicate(and quartz) glass resistance to thermal stress/shock.

Quote: Originally posted by Marvin

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]

In what possible scenario would a distillation flask under constant heat from either a hotplate + sandbath or heating mantle would the temperature differential of the glass get anywhere near the limits required for borosilicate glass to fracture?(which is roughly 160*c)

Extra points if it's explained how you intend to join the quartz flask to the borosilicate stillhead and expect it to have a higher chance of surviving.

Conditions within a laboratory setup/reaction need to be ridiculously volatile to require the use of quartz glass.

Short of unscrewing the thermometer adapter and pouring water or some organic compound directly into the boiling flask mid-distillation, the only source of heat in the entire procedure will be the hotplate itself. Unless the laws of thermodynamics changed recently, vaporization doesn't release heat.

[Edited on 20-4-2015 by Mesa]

[Edited on 20-4-2015 by Mesa]

byko3y - 19-4-2015 at 18:54

Water cooled condenser is a recipe for your disaster. It's okay to have all-borosilicate setup, until you don't have 310°C bumping acid gas separated by 2 mm of glass from a 30°C water.
And once again, even if you are sure there would be no real danger to the glass by a thermal shock - you might crack the glass mechanically, thus few drops of a cold water may come into contact with acid wapor, leading to rapid condensation sucking the water further into the flask filled with boiling sulfuric acid - boom.

[Edited on 20-4-2015 by byko3y]

macckone - 20-4-2015 at 19:55

Traditionally lead or ceramic retorts were used with air cooling.
A good quality borosilicate retort might be better.
Just wish I had a source for a quartz or high temp ceramic one.

Deathunter88 - 21-4-2015 at 07:36

Just found an online supplier in China who sells concentrated sulphuric acid drain cleaner. It look like reagent grade except it is just slightly cloudy. Its the only one I know of that sells is in China.

Here: http://item.taobao.com/item.htm?spm=a1z09.2.9.257.giwjG2&...

Don't be discouraged by the dark brown colour in the photo. Mine looked completely white when it arrived.

PS. Wooo, 50th post

[Edited on 21-4-2015 by Deathunter88]

Trizocy - 21-4-2015 at 13:41

Thanks deathhunter88

wg48 - 12-8-2016 at 14:18

I want to concentrate my 30% sulphuric acid. I don't want to waste any of it so I will use a 280mm Vigreux column in a all glass distillation set up.

I estimate the column is equivalent to 2 to 4 theoretical plates.

From the attached graph I estimate:
at 98% acid (boiling temp.) the vapour is 80% acid
at 80% acid (boiling temp.) the vapour is 4% acid
at 4% acid (boiling temp.) the vapour is <0.01% acid

Now I have to remove most of the water ie approximately 70% (water) of the original acid/water to reach 98%.
With two theoretical plates at the end approximately 4% of the distillate will be acid which on average is 2%(start to finish) of the 70% ie <1.5% of the acid will be lost.
With three or more theoretical plates the loss of acid will be <1%. Starting from 1 litre I will produce at least 0.28 litres of 98% acid

Do I have above about correct?

Attachment: Sulfuric Acid & Water - Liquid Vapor Equilibrium Concentration.pdf (328kB)
This file has been downloaded 618 times

[Edited on 12-8-2016 by wg48]

Metacelsus - 12-8-2016 at 14:51

You should be aware that using a Vigreux column will make it take a lot longer.

wg48 - 12-8-2016 at 15:01

Quote: Originally posted by Metacelsus

You should be aware that using a Vigreux column will make it take a lot longer.

Can you be a bit quantitative how many hours approximately?

[Edited on 12-8-2016 by wg48]

Deathunter88 - 12-8-2016 at 23:45

Quote: Originally posted by wg48

Quote: Originally posted by Metacelsus

You should be aware that using a Vigreux column will make it take a lot longer.

Can you be a bit quantitative how many hours approximately?

[Edited on 12-8-2016 by wg48]

I'd be willing to bet that little or none will be collected unless you insulate it very well. I have used a 300mm as an air cooled condenser for distilling sulphuric acid and it does a good job of condensing most/all of the acid.

wg48 - 13-8-2016 at 07:35

Quote: Originally posted by Deathunter88

Quote: Originally posted by wg48

Quote: Originally posted by Metacelsus

You should be aware that using a Vigreux column will make it take a lot longer.

Can you be a bit quantitative how many hours approximately?

[Edited on 12-8-2016 by wg48]

I expect to be collecting water with approximately 1% acid so the top of the column should be just over 100C. Yes I may well need insulation presumable but not too much as I want condensation over the whole column or it will not be fractionating.

ave369 - 25-8-2016 at 10:55

I have a personal method of sulfuric acid distillation. It involves two-step cooling: first you air-cool it in the "nose" of a retort. Second, you water-cool it in a Liebig which is connected to the nose of the retort. Thus you can avoid thermal shock. Also, no horrible acid smoke: it all condenses at 3-4 cm from the hot end of the Liebig.

[Edited on 25-8-2016 by ave369]