Eithern
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Elemental sulfur from CS2
Hello! In the lab I work we use carbon disulfide, not much maybe a liter every two months, but I was wondering if instead of dispose of like dangerous
wastes, could be possibile to decompose it to elemental sulfur.
I know that during combustion in a container a little sulfur is produced as a yellow deposit, but do you know other methods that are more clean and
efficient? Thanks!
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Precipitates
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Heat, and an oxygen-free environment, but it's probably not easy.
Attachment: Formation of Solid Sulfur by Decomposition of Carbon Disulfide in the Oxygen-Lean Cold Plasma Environment.pdf (90kB)
This file has been downloaded 29 times
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unionised
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Sell CS2: buy sulphur.
Seriously, CS2 is more valuable.
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chempyre235
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Yeah, the average price I could find with a Google search was around 300 USD per liter.  There weren't many companies even selling this chemical, and it is restricted to ground shipments.
[Edited on 3/6/2025 by chempyre235]
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Texium
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This is pure blasphemy given that CS2 is an incredibly unique, expensive, and hard to acquire solvent, while elemental sulfur is so cheap
and plentiful that every amateur chemist probably has at least a kilo sitting around that they don’t know what to do with! 
Also, carbon disulfide is really nasty stuff. If you’re going to play around with it, at least use it for something worthwhile. Figuring out a way
to turn it into something as cheap and dull as elemental sulfur is not worth the risk to your health.
[Edited on 3-6-2025 by Texium]
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Texium
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Thread Moved
6-3-2025 at 07:36 |
Sulaiman
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opinions (of a non-chemist that can be ignored)
I presently have no CS2 but when I did, I was not inclined towards distillation due to fire risk.
Unless such distillations are common in your lab,
the return may not be worth the risk.
Similarly for anything involving combustion.
If you are considering taking waste off site then there may be liability problems for the lab.
(assuming that you are not a registered waste disposal company)
In either case you should have a quiet word with your supervisor before expending too much effort.
I have usually found no problems when asking for stuff of little/no/negative value.
Sometimes a nominal sum may be involved just to keep paperwork tidy.
So, although your intentions are excellent,
you should get at least tacit approval - for your own 'safety'
PS imagine sitting in your car, in a traffic jam, in summer, with a few litres of CS2 in the trunk/boot.
bp 46oC, autoignition at 102oC (eg the exhaust system)
[Edited on 6-3-2025 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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Eithern
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Yes I did find the same but is not something I can do with my possibilities
Quote: Originally posted by Texium  | This is pure blasphemy given that CS2 is an incredibly unique, expensive, and hard to acquire solvent, while elemental sulfur is so cheap
and plentiful that every amateur chemist probably has at least a kilo sitting around that they don’t know what to do with!
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Ahah I know! But of course the CS2 I'm talking about is more or less contaminated with volatile compounds and therefore worthless, that's why I liked
the idea of converting a toxic waste in a common but safe substance.
| Quote: Originally posted by Sulaiman |
If you are considering taking waste off site then there may be liability problems for the lab.
(assuming that you are not a registered waste disposal company)
In either case you should have a quiet word with your supervisor before expending too much effort.
I have usually found no problems when asking for stuff of little/no/negative value.
Sometimes a nominal sum may be involved just to keep paperwork tidy.
So, although your intentions are excellent,
you should get at least tacit approval - for your own 'safety'
PS imagine sitting in your car, in a traffic jam, in summer, with a few litres of CS2 in the trunk/boot.
bp 46oC, autoignition at 102oC (eg the exhaust system)
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Well you're right, but I'm talking of very small (but not less dangerous) quantities, a few mL at time.
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DraconicAcid
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If you want to get rid of it, burn it, and run the vapours the an alkali trap.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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teodor
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Why not use it to prepare thiocarbonates and purify them by recrystallization to get rid of impurities.
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DraconicAcid
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| Quote: Originally posted by teodor | | Why not use it to prepare thiocarbonates and purify them by recrystallization to get rid of impurities. |
That, too.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Eithern
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| Quote: Originally posted by teodor | | Why not use it to prepare thiocarbonates and purify them by recrystallization to get rid of impurities. |
Uhm but I have no uses for them, while solid sulfur, although cheap, is "cool" and I don't have it. Suggestions?
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teodor
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| Quote: Originally posted by Eithern | | Quote: Originally posted by teodor | | Why not use it to prepare thiocarbonates and purify them by recrystallization to get rid of impurities. |
Uhm but I have no uses for them, while solid sulfur, although cheap, is "cool" and I don't have it. Suggestions? |
But you probably can sell the thiocarbonate on ebay and buy more sulfur.
A lot of people have no access to CS2, and I think it is possible to synthesize it from thiocarbonate.
[Edited on 18-3-2025 by teodor]
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DraconicAcid
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I thought I posted this once already, but xanthates and thiocarbonates are definitely cool.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Keras
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| Quote: Originally posted by Eithern |
Ahah I know! But of course the CS2 I'm talking about is more or less contaminated with volatile compounds and therefore worthless, that's why I liked
the idea of converting a toxic waste in a common but safe substance.
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Distill it to get a purer compound.
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Radiums Lab
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@Keras Distilling CS2 is no joke because it ignites easily.
The oxygen free atmosphere is hard to create or maintain.
[Edited on 19-3-2025 by Radiums Lab]
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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Dr.Bob
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If you react the CS2 with F2, you can make trifluoromethyl-sulfurpentafluoride, althought it may be contaminated with SF4, which is highly toxic.
That was one of the first fluorine reactions that my friend Ed discovered back in the 1960s or 70s. The EPA used it as a tracer for smokestack
emissions many years ago, as it could be detected at very small concentrations back years ago. Now we can detect almost anything at tiny
concentrations.
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j_sum1
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IMO, this thread is less about making sulfur and more about safe disposal or recycling of contaminated CS2.
I would think the best bet is to recover the CS2 without reacting it with anything.
My first attempt would be vacuum distillation at room temperature, probably running chilled brine through the condenser and having the
receiving flask sitting in dry ice.
Second attempt would be short path distillation done, you know, as an actual short path distillation. That is, distillation at below boiling
temperature from the vapour pressure alone.
By all means, attempt to recover something useful from what would otherwise be a toxic and volatile waste material. But I think attempts to make
sulfur or react with fluorine are misguided.
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RU_KLO
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The substance can be contacted with the iron either directly or indirectly. Such contacting includes passing the substance through a permeable body of
iron.
Iron, generally zero-valent iron, destroys carbon disulfide by a chemical redox reaction
Methods of carbon disulfide treatment
https://patents.google.com/patent/WO2003095118A1/en
Go SAFE, because stupidity and bad Luck exist.
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Sulaiman
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I would probably take some (100ml?) and 'have a play' with it.
boil it, burn it, do like the ether demo - put in a (remote) flat surface a burning candle then nearby a small dish of CS2, prepare for soot!
Do all kinds of stupid stuff that you could not do at work.
(ppe, safety, blah blah blah. just use small quantities, and keep the larger quantity far away)
Sounds frivolous or unwise BUT not really that hazardous if you have (maybe not so) common sense,
and you will have a more realistic idea of the risks.
One exposure to a little CS2 vapour will not kill you.
Judge for yourself the fire risks.
I dislike the smell and the fire risks but if you want it .....
or
leave it alone
not much to be learned inbetween.
PS out of curiosity I checked my favourite online shopping site
500ml carbon disulphide with p&p equivalent USD40
[Edited on 20-3-2025 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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teodor
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I don't have much interest here, but noticing that Sulaiman wrote something here and having 5 minutes to read
- why wouldn't use good old "decolorising carbon" to remove most of organics before further treatment
- stay away from distillation if you don't know exactly how to deal with fire on your workplace
And I of course enjoy the way how Sulaiman frames safety standards here.
[Edited on 20-3-2025 by teodor]
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Eithern
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Thank you all for your interest in the topic, I should add that unfortunately I don't have an adeguate setup at home for using toxic volatile
substances, and at work I can only do something when I've a free moment.
Obviously my superiors are not interested in recycling or re-valuating chemicals, we're an analysis laboratory not a place of research, so a delicate
procedure like distillation is off limits. Making thiocarbonates seems easier but like I said before I don't know what to do with them, but if someone
here is interested to buy some I could make a try
Joking aside, as Sulaiman suggested, I indeed took a few milliliters and ignited them with a lot of precautions to see if the reaction is like I saw
on YT, can confirm that it's nothing special, blue faint flame with a strong smell of SO2, and a yellow deposit was effettively formed on the
container edges... yeee that's my sulphur! Too bad it's only a few milligrams! Very inefficient 
Could I capture and bubble the SO2 in hydrogen peroxide to make sulfuric acid? I don't know, maybe I should just let it be disposed of as usual and
focus on recovering other things, but argh this bothers me!
If you have any other ideas they are welcome.
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Precipitates
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Yes, an old video now, but still good on the subject:
Make Sulfuric acid (metabisulfite/oxidizer method)
Instead of a sulfur candle, carbon disulfide could, at least theoretically, be burned alternatively.
A method of capturing sulfur dioxide gas is shown in the following video, also by Nurdrage:
3 Ways to Make Sulfur Dioxide Gas
Just note the extreme flammability of carbon disulfide (as mentioned previously) - fire safety protocols should be in place.
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