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Author: Subject: "Let's Distill Some H2SO4!" -Last Words
AndrewOfWallachia
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[*] posted on 27-4-2024 at 08:48
"Let's Distill Some H2SO4!" -Last Words


So, Soon, as soon as I get my rickety Bunsen burner to work. I want to set out on my first -true- journey. That is concentrating some Sulfuric Acid drain cleaner into ~98% Sulfuric Acid. I've worked out an idea of what I have to do and how I will do it, but I need some confirmation that these will work and --absolutely-- any and every tip you can bestow upon me!
So, let's begin:
-According to density calculations (done with a cheap precision scale and 10ml plastic syringe) the Drain Cleaner should be around 85% Conc. with quite a bit of crap added to it (It is very brown and quite viscous).
-My set-up will consist of a round bottom 3-neck flask, connected to an elbow, and a simple distillation column, running through a vacuum adaptor elbow (which will serve as a vent so that there is no pressure difference inside and outside the system) into a smaller 1 neck flask.
-The starting flask will be filled half-way with Drain Cleaner, I will smash a ceramic flowerpot and use it's shards as boiling chips in the starting flask, which I will heat with a Bunsen burner constantly.
-I don't know if or not to cool the condenser with water or just leave it air-cooled without any forced air. You're going to have to brief me on that.
-I can (hopefully) monitor the rough temperature of the starting flask with a cheap IR thermometer that I got. But I have no feasible way of measuring the vapor temperature inside the stillhead.
-After adding the Drain Cleaner and boiling chips to the starting flask, I will close it off, and start heating it. I will eventually start getting some water-rich distillate, but when I see white fumes rising through the condenser I will switch out the receiving flask. At that moment I will be distilling 98% Sulfuric Acid into the receiving flask, correct? I will also check the temperature of the starting flask to make sure it's around 337C but I don't know how reliable that is.
-After most of the liquid in the starting flask has boiled off, I will stop heating, and leave everything untouched until it cools, good?
-Once cool, I can collect the Concentrated Sulfuric Acid form the receiving flask, and and dispose of what's left in the starting flask.
-I will leave all parts of the set-up in a bath of Sodium Bicarbonate solution and then rinse them very well, is it adequate?
-My Glassware is bought from a company called VEVOR, they claim it's 3.3 Borosilicate glass which I read from a different source can stand up to 450C. If you've worked with this type of glassware before, is it reliable/safe?
That's how I envision the procedure taking place, please let me know of any problems or complications that might arise and how to fix or avoid them, correct me if any part of my procedure is wrong and be sure to give me any tips that might help. Thanks a lot in advance I hope I will live through this baptism of fire so that I can finally start doing real chemistry.:D


[Edited on 27-4-2024 by AndrewOfWallachia]
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[*] posted on 27-4-2024 at 09:18


Nurdrage recently released a video on this very topic. It’s very informative.
Even with the ceramic boiling chips you are probably going to have extreme bumping. Don’t use a flask you value as it’s likely to get damaged.




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[*] posted on 27-4-2024 at 16:48


Do not cool the condenser with water. Air cooling should be sufficient. You want to keep all water away from boiling concentrated sulfuric acid. If anything goes amiss there will be instant regret with high-order consequences.

Have some kind of containment setup and an evacuation strategy for if your glassware fails. A large metal tray filled with sand underneath everything will be a good idea.

Use teflon plumbers' tape on your glass joints. You do want to be able to get them apart afterwards and having a bit of flex for glass expansion is a good idea.

Let your glass cool completely before disassembly. I would not be using bicarb. You will get a very vigorous reaction and lots of gas evolution the instant it makes contact with concentrated acid. Pour your flask waste slowly into a large bucket of water. Then dispose of this diluted stuff as waste. Add water slowly to your glassware. I use a spray bottle for this kind of thing. Then when it looks like it will be manageable, you can rinse in a bucket of water.

I confess to never having the experience of distilling sulfuric acid. Two reasons: I have not had a need: my sources of H2SO4 are pretty clean. Second, I do not trust most of my cheap glassware at flame temperatures. I have had experience in boiling down home made sulfuric acid in a beaker to concentrate it. That was enough for me to know that hot concentrated sulfuric acid deserves a lot of respect.
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[*] posted on 27-4-2024 at 19:05


A section right at the beginning of Vogel's A Textbook of Practical Organic Chemistry (here) deals with superheating and bumping during distillations, and chances are you will see a good deal of bumping. A suggestion he gives is enough glass wool in the flask to rise 5 mm above the surface of the liquid. At least it will be kind to your rbf.

Make sure you have enough boiling chips in the flask. Don't be stingy with them.

See if you can discover what else is in the drain cleaner (by contacting the manufacturer, for example). You'll be heating whatever the filler is together with a strong acid that happens to be a formidable dehydrating agent. The result may range from good (~98% sulfuric acid) to acceptable (funny smell or odd color in the distillate) to really bad (the whole place smells like Death itself and the boiling chips are sort of glued to the round bottom flask). They put almost anything as filler these days and you need to know what you're up against.

A safety tip: if you see something going wrong and it has nothing to do with gas leak, don't try to fix it. Turn off the gas and run away as fast as possible. You can always buy new equipment but not new fingers.




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[*] posted on 27-4-2024 at 22:42


Distillation should be performed slowly, and outside to reduce the health hazard (and damage) if the glassware does break.

Given the nature of this distillation (dangerous chemicals at high temperatures), I'd perform several basic quick distillations to get to know your glassware, if you have not done so already, and to foresee any problems that may occur before you start using sulphuric acid i.e., check for any dodgy joint seals etc.,.

I haven't distilled sulphuric acid, but have distilled bromine, so know the importance of being comfortable with your glassware!

[Edited on 28-4-2024 by Precipitates]
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[*] posted on 27-4-2024 at 23:34


Quote: Originally posted by j_sum1  
Do not cool the condenser with water. Air cooling should be sufficient. You want to keep all water away from boiling concentrated sulfuric acid. If anything goes amiss there will be instant regret with high-order consequences.


Really, for distilling concentrated sulphuric acid I'd use a quartz RBF. Is more expensive, sure, but I'd be much more confident in it. Also as condenser I'd use a simple tube of boro 3.3 glass of, say, 40 to 50 cm, with joints at either end.

If bumping is problematic, you might be able to source glass magnetic stir bars. They’re inexpensive. Apparently, teflon coated ones resist boiling sulphuric acid, but I wouldn't bet the farm on it.

And oh, edit: use a heating mantle, not a hot plate. Heating mantles minimise thermal stress, which is paramount here.

[Edited on 28-4-2024 by Keras]
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[*] posted on 27-4-2024 at 23:50
my 2cents worth


Assume 'condenser' not 'column'

I'd have to check but I guess that a single distillation will not get 98% from <90%,
probably <95%.

If your apparatus is sealed except for the vacuum take off on the elbow,
when the acid bumps it will most likely blow open one or more of your joints!
Leave the end of your condenser open,
and EXPECT AND PREPARE FOR violently ejected hot acid.
It may easily spray over a metre away!!

I've not tried glass wool, maybe I will.
Whatever you use as 'boiling chips' start with it dry.
(don't try the yellow/treated glass wool used for thermal insulation)

If your budget allows, I suggest buying an air condenser, which is just a plain tube,
(that can also be used as a Hempel column or chromatography column)
I see many people using a water cooled condenser,
so obviously it can be done,
but the stress on the glass and the risk of mixing boiling sulphuric acid with water,
makes it a worthwhile investment.

Even without water the differential thermal expansion will severely stress your glass due to hot inner and cold outer tubes.
R
I used a Leibig after my air condenser to cool the distillate, but it wasn't necessary.

I used no joint sealer (grease, ptfe tape etc.) as the joints self-seal with condensed sulphuric acid.

No plastic Keck clips, thermometer holders etc. due to temperature.

An open flame with cheap Chinese glassware works just fine.




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[*] posted on 28-4-2024 at 00:37


Quote: Originally posted by Sulaiman  
Assume 'condenser' not 'column'

I'd have to check but I guess that a single distillation will not get 98% from <90%,
probably <95%.

If your apparatus is sealed except for the vacuum take off on the elbow,
when the acid bumps it will most likely blow open one or more of your joints!
Leave the end of your condenser open,
and EXPECT AND PREPARE FOR violently ejected hot acid.
It may easily spray over a metre away!!

I've not tried glass wool, maybe I will.
Whatever you use as 'boiling chips' start with it dry.
(don't try the yellow/treated glass wool used for thermal insulation)

If your budget allows, I suggest buying an air condenser, which is just a plain tube,
(that can also be used as a Hempel column or chromatography column)
I see many people using a water cooled condenser,
so obviously it can be done,
but the stress on the glass and the risk of mixing boiling sulphuric acid with water,
makes it a worthwhile investment.

Even without water the differential thermal expansion will severely stress your glass due to hot inner and cold outer tubes.
R
I used a Leibig after my air condenser to cool the distillate, but it wasn't necessary.

I used no joint sealer (grease, ptfe tape etc.) as the joints self-seal with condensed sulphuric acid.

No plastic Keck clips, thermometer holders etc. due to temperature.

An open flame with cheap Chinese glassware works just fine.


So, 100% sure that the glassware I have will resist a Bunsen flame? Also, should I use metallic clips? I can't get a reliable heating mantle, or a quartz RBF because they are simply way too rare here. Also, even when using boiling chips, I can expect bumping, how should I react if it bumps?
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[*] posted on 28-4-2024 at 00:39


Quote: Originally posted by Precipitates  
Distillation should be performed slowly, and outside to reduce the health hazard (and damage) if the glassware does break.

Given the nature of this distillation (dangerous chemicals at high temperatures), I'd perform several basic quick distillations to get to know your glassware, if you have not done so already, and to foresee any problems that may occur before you start using sulphuric acid i.e., check for any dodgy joint seals etc.,.

I haven't distilled sulphuric acid, but have distilled bromine, so know the importance of being comfortable with your glassware!

[Edited on 28-4-2024 by Precipitates]

Well, I have preformed about two of those... the first one I did I managed to crack one of my starting flasks right away... Though it's highly likely that was because I let all of the liquid boil off before shutting off the heating.
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[*] posted on 28-4-2024 at 03:25


Quote: Originally posted by AndrewOfWallachia  

Well, I have preformed about two of those... the first one I did I managed to crack one of my starting flasks right away... Though it's highly likely that was because I let all of the liquid boil off before shutting off the heating.


Yeah that would do it! ;)
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[*] posted on 28-4-2024 at 03:51



So, 100% sure that the glassware I have will resist a Bunsen flame?
... No, I wouldn't guarantee ANY glassware 100%
So prepare for total chaos in any case.
(for me that means staying as far upwind as possible with a hosepipe ready)

Also, should I use metallic clips?
... Yes, mine (cheap) were not completely invulnerable to hot sulphuric acid vapours.

.. neither a reliable heating mantle nor a quartz RBF are required.
An open flame with the flask well above the flame works well.
I made a 'chimney' around the flame and flask due to wind, it worked really well as a hot air bath equivalent

... Put sand or equivalent as a target,
then, after bumping occurs,
thank whichever deity you believe in for saving you from an awful fate ;)




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[*] posted on 28-4-2024 at 05:39


Quote: Originally posted by Sulaiman  
I'd have to check but I guess that a single distillation will not get 98% from <90%,
probably <95%.

That's more like it.

Quote: Originally posted by Sulaiman  

I've not tried glass wool, maybe I will.
Whatever you use as 'boiling chips' start with it dry.
(don't try the yellow/treated glass wool used for thermal insulation)

Thank you. I always forget that that yellow stuff is glass wool too. The glass wool should be like this: glass wool from Carl Roth. You may want to see the MSDS at the bottom of the page to see if that one in particular is adequate.

There's a ten-year-old thread about sulfuric acid distillation. Check it out: https://www.sciencemadness.org/whisper/viewthread.php?tid=61...




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[*] posted on 28-4-2024 at 14:09


Quote: Originally posted by AndrewOfWallachia  

-My Glassware is bought from a company called VEVOR, they claim it's 3.3 Borosilicate glass which I read from a different source can stand up to 450C. If you've worked with this type of glassware before, is it reliable/safe?


[Edited on 27-4-2024 by AndrewOfWallachia]


The Vevor brand takes a wide range of cheap products and slap their own brand on it, the quality of their products is highly variable.
I would suggest a test run using just water, but having all else the same. Also, as others have suggested already, make sure your set up allows for a glass failure.
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[*] posted on 29-4-2024 at 04:08


Quote: Originally posted by B(a)P  
Quote: Originally posted by AndrewOfWallachia  

-My Glassware is bought from a company called VEVOR, they claim it's 3.3 Borosilicate glass which I read from a different source can stand up to 450C. If you've worked with this type of glassware before, is it reliable/safe?


[Edited on 27-4-2024 by AndrewOfWallachia]


The Vevor brand takes a wide range of cheap products and slap their own brand on it, the quality of their products is highly variable.
I would suggest a test run using just water, but having all else the same.

Temperature would be very different.
A common liquid that does have distillation range close to that of sulphuric acid (340 C) is diesel fuel.
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[*] posted on 29-4-2024 at 06:58


Be very careful if you try that though, as diesel fuel in variable glassware over an open bunsen flame sounds dodgy! Cooking oils or something random like vaseline may be safer.
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[*] posted on 29-4-2024 at 12:00


Quote: Originally posted by chornedsnorkack  
Quote: Originally posted by B(a)P  
Quote: Originally posted by AndrewOfWallachia  

-My Glassware is bought from a company called VEVOR, they claim it's 3.3 Borosilicate glass which I read from a different source can stand up to 450C. If you've worked with this type of glassware before, is it reliable/safe?


[Edited on 27-4-2024 by AndrewOfWallachia]


The Vevor brand takes a wide range of cheap products and slap their own brand on it, the quality of their products is highly variable.
I would suggest a test run using just water, but having all else the same.

Temperature would be very different.
A common liquid that does have distillation range close to that of sulphuric acid (340 C) is diesel fuel.


Yes agreed the temperature of water distillation is much lower than sufuric acid, though the boiling vessel will still be subjected to a flame to heat it, which puts quite a bit of stress on glass. I am not saying if it survives water distillation it will definitely survive sulfuric acid distillation, though if there is a a major flaw in the glass it may well present itself when heated with with a gas flame while distilling water. The bonus here is that you get a bit of a mess to clean up, but likely no serious damage to equipment. Water is also near freely available, easy to clean up and distilled water is useful.
The issue with diesel is that if the glass fails your lab burns down. Personally, if I had to pick between distilling diesel and sulfuric acid and having a glass failure over a flame I would go the acid.
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[*] posted on 29-4-2024 at 14:11


Quote: Originally posted by chornedsnorkack  
A common liquid that does have distillation range close to that of sulphuric acid (340 C) is diesel fuel.

He intends to use a Bunsen burner in the distillation, so diesel is a no-no. There's even the risk that the joints are very crappy indeed--if we consider that Vevor just puts its name in cheap and probably uncertified glassware--and flammable vapor leaks everywhere and there goes the lab. Soybean or sunflower oil are better options, both being good until about 220 °C.

One addition to what @B(a)P suggested: add some ammonia to the water in the flask. This way you can find leaks in the joints by using a test tube with some hydrochloric acid. A leak will leave a small cloud of ammonium chloride.




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[*] posted on 29-4-2024 at 18:07


I would want to perform all of these experiments outside - fires are just so much easier to deal with, and you can let them burn (within reason). Cooking oil fires can also be damaging, and burn down your lab!

If you do do the distillation inside - babysit the reaction, have a bucket of sand (or sand underneath the apparatus as previously suggested) and a fire extinguisher at the ready :D

If the glassware is sound, it's less of a concern. In any case, it's going to need a nice soapy bath after any cooking oil distillations!
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[*] posted on 1-5-2024 at 04:11


Quote: Originally posted by bnull  
Quote: Originally posted by chornedsnorkack  
A common liquid that does have distillation range close to that of sulphuric acid (340 C) is diesel fuel.

He intends to use a Bunsen burner in the distillation, so diesel is a no-no. There's even the risk that the joints are very crappy indeed--if we consider that Vevor just puts its name in cheap and probably uncertified glassware--and flammable vapor leaks everywhere and there goes the lab. Soybean or sunflower oil are better options, both being good until about 220 °C.

One addition to what @B(a)P suggested: add some ammonia to the water in the flask. This way you can find leaks in the joints by using a test tube with some hydrochloric acid. A leak will leave a small cloud of ammonium chloride.
I could try that with sunflower seed oil. However I assume that I will get not distillate (1) and that the glassware is going to be a nightmare to clean (2) and that (3) it will still not reach nearly was close to the 337C boiling point of H2SO4.
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[*] posted on 1-5-2024 at 04:12


Quote: Originally posted by Precipitates  
Quote: Originally posted by AndrewOfWallachia  

Well, I have preformed about two of those... the first one I did I managed to crack one of my starting flasks right away... Though it's highly likely that was because I let all of the liquid boil off before shutting off the heating.


Yeah that would do it! ;)

Please elaborate?
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[*] posted on 1-5-2024 at 04:14


Quote: Originally posted by bnull  
A section right at the beginning of Vogel's A Textbook of Practical Organic Chemistry (here) deals with superheating and bumping during distillations, and chances are you will see a good deal of bumping. A suggestion he gives is enough glass wool in the flask to rise 5 mm above the surface of the liquid. At least it will be kind to your rbf.

Make sure you have enough boiling chips in the flask. Don't be stingy with them.

See if you can discover what else is in the drain cleaner (by contacting the manufacturer, for example). You'll be heating whatever the filler is together with a strong acid that happens to be a formidable dehydrating agent. The result may range from good (~98% sulfuric acid) to acceptable (funny smell or odd color in the distillate) to really bad (the whole place smells like Death itself and the boiling chips are sort of glued to the round bottom flask). They put almost anything as filler these days and you need to know what you're up against.

A safety tip: if you see something going wrong and it has nothing to do with gas leak, don't try to fix it. Turn off the gas and run away as fast as possible. You can always buy new equipment but not new fingers.

I don't think I can reasonably get the glass wool you suggest for this. Contacting the manufacturer, is uh... well, risky, if even possible at all since a young guy inquiring what crap they put in their sulfuric acid containing product might raise some eyebrows. And three, really important, you say "Don't be stingy with boiling chips", I got that! But, is there such a thing as *too many* boiling chips?

[Edited on 1-5-2024 by AndrewOfWallachia]
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[*] posted on 1-5-2024 at 05:50


Quote: Originally posted by AndrewOfWallachia  
Quote: Originally posted by Precipitates  
Quote: Originally posted by AndrewOfWallachia  

Well, I have preformed about two of those... the first one I did I managed to crack one of my starting flasks right away... Though it's highly likely that was because I let all of the liquid boil off before shutting off the heating.


Yeah that would do it! ;)

Please elaborate?


Flasks are definitely more likely to crack if you distill until dryness.

Although upon distilling sulphuric acid, the bumping may mean you have to stop with a proportion of liquid still in the flask anyway.
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[*] posted on 1-5-2024 at 10:54


Quote: Originally posted by AndrewOfWallachia  
I could try that with sunflower seed oil. However I assume that I will get not distillate (1) and that the glassware is going to be a nightmare to clean (2) and that (3) it will still not reach nearly was close to the 337C boiling point of H2SO4.

The use of sunflower oil is to see if the glassware resists heating. Much better than have hot acid spilling everywhere. It won't be distilled, of course.

To clean the flask, you can use a diluted solution of NaOH with common detergent. After draining most of the oil, add a small quantity of the solution and swirl it. Drain the flask, add more fresh solution, swirl and drain again. You can repeat until you're satisfied and then wash with water.

Quote: Originally posted by AndrewOfWallachia  
I don't think I can reasonably get the glass wool you suggest for this.
It was just an idea. Since you won't be using vacuum, the boiling chips will do (even if they don't eliminate the bumping completely).

Quote: Originally posted by AndrewOfWallachia  
Contacting the manufacturer, is uh... well, risky, if even possible at all since a young guy inquiring what crap they put in their sulfuric acid containing product might raise some eyebrows.

It's not risky, unless you say you're going to boil it. That's one kind of information that must be publicly available for safety and medical reasons (although they may be dodgy and use "trade secret" for some substances and broad percentage ranges--in motor oils, for example). Some manufacturers include in the label an e-mail address or phone number where you can ask for the MSDS of the product; some have it for download on their website. Or you can use Google to find the MSDS, just type "drain cleaner MSDS" plus the brand.

Or even the registration of the product within a governmental agency as a last resort (here's an example from Argentina: https://www.argentina.gob.ar/anmat/regulados/productos-de-us...). I don't know who handles that in Romania, you'll have to check that.

Quote: Originally posted by AndrewOfWallachia  
And three, really important, you say "Don't be stingy with boiling chips", I got that! But, is there such a thing as *too many* boiling chips?
About a spoonful should do (I'm assuming the chips are bean-sized or smaller). It is about 1 L of acid, right?



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[*] posted on 2-5-2024 at 08:44


I think you can use too many boiling chips. While distilling ethylene glycol (b.p. 197 C), using more boiling chips and sand caused worse bumping than when I used less. I think too much acts as insulation, causing the bottom off the flask to superheat.
Also, if you want to do a practice run, try distilling ethylene glycol. It's not as high as sulfuric acid, but it will give you a better idea than water.




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[*] posted on 12-6-2024 at 06:05


I did this once. It was pretty terrifying!! Worked well enough though.
I used a hiking gas stove for heat and was very careful to move it around by hand while getting up to temperature so as to not shock the glass. Not very much fun being that close to such a hot flask of angry acid! Used plenty of boiling stones. I'd say be conservative with how much you fill the flask as there was still a fair bit of bumping.

I have a 400 degree thermometer so could make sure what temp it came over at.

I am very glad I've found a local online source recently and so hopefully won't need to do this again!
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