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Author: Subject: Distilling Sulfuric Acid
Ludus
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[*] posted on 3-3-2020 at 20:18
Distilling Sulfuric Acid


Hello,

Some time ago I acquired a sizable amount of 90-93% sulfuric acid for very cheap; however, the downside is that, being drain cleaner, has dyes and other junk in it. I have tried boiling it with H2O2 to some effect, although I’m still left with a slight yellow tinge. I shouldn’t worry about it, but I’m one of those stubborn chemists who likes pure chemicals. I tried distilling a small amount (about 150mL) utilizing a sand bath and a camp stove to try to prevent thermal shock. This process took about 4 hours of babysitting, but it worked, no more detritus. I want to do this again although I’m scared to use other methods as I'd prefer not to have sulfuric acid spilling in my lab.
Maybe y’all could shed some light on your experiences or ideas.

Thanks,
-Lud
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draculic acid69
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[*] posted on 3-3-2020 at 20:47


If u found something that works well and isn't difficult stick with it.how much pure h2so4 do you need anyway? Most of what I use it for can be done with it as it comes out of the bottle.only thing I'd need pure distilled h2so4 for is if I was making something I was going to ingest.like foodgrade sodium sulfate
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[*] posted on 3-3-2020 at 23:39


Sulfuric acid has a very high boiling point and in my opinion is at the border of what can be done with glass. I would not feel very comfortable distilling sulfuric acid as it requires 300+ C temperatures.

I would distill a small amount, e.g. 250 ml and only use that for critical experiments, such as doing experiments with transition metal complexes or for preparation of pure metal sulfates. For many other types of reactions (e.g. as catalyst for esterification reactions, for nitrating things, for making HNO3) the other type of acid is perfectly fine. E.g. when you make HNO3, then the dyes and other crap remain behind and/or are destroyed and only HNO3 distills over.

Your method of distilling sounds very reasonable and indeed I would stick with that method if it works for you and take the 4 hour babysitting for granted. You won't need to do that very often. Take a good book, install yourself and make your chemistry hobby a relaxing one ;)




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draculic acid69
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[*] posted on 4-3-2020 at 00:50


Yeah like women said unless purity is critical I would not bother as your pushing the limits of the glass and if it does break imagine having to deal with the boiling sulfuric fumes and the destruction of a spill.if u have a few litres of something and need it all pure I'd just do it as needed.
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Ludus
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[*] posted on 4-3-2020 at 08:05


So far most of my uses for H2SO4 don't require it to be pure, the drain cleaner stuff works just fine. I guess I'll find a day to set aside time distill some so I wont have to do it again.
Relatively speaking I'm pretty new to amateur chemistry, and I have to take the waiting in stride.
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[*] posted on 4-3-2020 at 10:26


Commercially pure 98% sulfuric acid is made by combining fuming sulfuric acid with distilled water obviously adding fuming to water. 30% Fuming sulfuric (30% oleum) is made by adding up to 30% sulfur trioxide to 98% sulfuric acid. Higher percentage fuming is made by adding more sulfur trioxide to 30% oleum.

One trick for a home chemist is placing distilled water and fuming in a drying or vaccum chamber and allowing the fuming to slowly absorb the water. This can be done with sulfur trioxide which has a much lower boiling point but is extremely dangerous to work with. For a home chemist seeking very high purity sulphuric acid, this is probably easier than distilling.

See this thread for making sulfur trioxide:
http://www.sciencemadness.org/talk/viewthread.php?tid=10217



[Edited on 4-3-2020 by macckone]
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[*] posted on 4-3-2020 at 10:55


I find that distilling sulphuric in a heating mantle under vacuum is easy, however it does take quite some time. Alternatively, you can purchase quartz flasks that can take open flame.



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[*] posted on 8-3-2020 at 07:43


I've don this a lot in my normal flasks after testing it.

I add to a 1L flask 500ml of H2SO4, a small amount of broken lab glass chips, 10ml of 35% peroxide.

Place this in a heating mantle and warm till the peroxide reaction kicks off and allow to react.

then standard simple distillation with joints sealed with H2SO4

Just have preparations if some thing does go wrong, so far I have don over 6+ L with out issue but I all ways monitor it and prepared for disaster.

[Edited on 8-3-2020 by XeonTheMGPony]
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[*] posted on 24-3-2020 at 16:34


Quote: Originally posted by Vosoryx  
I find that distilling sulphuric in a heating mantle under vacuum is easy, however it does take quite some time. Alternatively, you can purchase quartz flasks that can take open flame.


I just wanted to recommend the same.
Use vacuum or quarz flask.
If one needs analytical grade h2so4 recommended purification is distil. after h2o2 was added from a quartz distil. flask.

https://pubs.acs.org/doi/pdf/10.1021/ac60320a016
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