Sciencemadness Discussion Board - Very pure sulfur without recrystallization

Very pure sulfur without recrystallization

vano - 24-2-2021 at 04:47

Hi. I have developed a good method to get pure sulfur. There may be this method but I have not read it anywhere. This method is very simple, cheap and not need expensive and rare chemicals.

Reagents: sulfur, NaOH and citric acid or oxalic acid or other acids.

I used technical sulfur. I dissolved it in sodium hydroxide solution and made polysulfide. Next i filtered it and add citric acid solution slowly. Hydrogen sulfide and maybe other polysulfide produced(2 and 3?), but many sulfur stayed in solution. When polysulfide colour disappeared then i wash sulfur 5 times and filter with liter of water again. It has white colour, it think it is very pure and particles are very small, because many of them penetrated the filter paper.

Bedlasky - 24-2-2021 at 05:29

Quote: Originally posted by vano

This method is very simple, cheap and not need expensive and rare chemicals.

Toluene is quite cheap and common chemical.

Quote: Originally posted by vano

Hydrogen sulfide and maybe other polysulfide produced(2 and 3?), but many sulfur stayed in solution.

Polysulfides aren't form - they are unstable at room temperature, if you want to produce polysulfane oil, you must work below 0°C. Btw. not just hydrogen sulfide is formed, but also sulfur dioxide. Sulfur disproportionates in NaOH solution in to polysulfide and thiosulfate:

(x+2)S + 6NaOH --> 2Na2Sx + Na2S2O3 + H2O

Polysulfides decompose in acidic solution in to hydrogen sulfide and sulfur, but thiosulfate decompose in to variety of products like SO2, S, H2S, Na2SO4, maybe also in to polythionates. You may purified sulfur by this way, but you some of it lost in the form of various sulfur compounds. I think, that recrystallization from toluene is cheaper, less smelly and losses are minimal. You can recover your toluene and use it again for sulfur purification. But NaOH is definitely lost after this reaction.

unionised - 24-2-2021 at 05:34

You seem to have missed the bit where the H2S produced by decomposition of polysulphide in acid reacts with the SO2 produced by the reaction of acid with sulphites and thiosulphates .

H2S + SO2 --> S + H2O
(I will leave you to the joy of balancing that equation)
In principle, the sulphur is all reprecipitated when you acidify the stuff.

There will be some loss due to oxidation by air.

Bedlasky - 24-2-2021 at 05:49

2H2S + SO2 = 3S + 2H2O

But Vano's reaction produce (ideally) 1:1 H2S:SO2 mixture. In the mixture is slightly more H2S than SO2, because of other ways of thiosulfate decomposition. But still you have excess of SO2 + other side products.

Sulaiman - 24-2-2021 at 06:45

Quote: Originally posted by vano

... It has white colour, it think it is very pure and particles are very small...

have you tried melting some (m.p. 115.2 ^oC [106 t0 119]) ?
(about the same m.p. as iodine, 113.5)

[Edited on 24-2-2021 by Sulaiman]

vano - 24-2-2021 at 06:45

Quote: Originally posted by Bedlasky

Toluene is quite cheap and common chemical.

Polysulfides aren't form - they are unstable at room temperature, if you want to produce polysulfane oil, you must work below 0°C.

I know, but this is a other method, so I mentioned it in the title. Also everyone don't have toluene and xylene.

I do not think so. Ammonium polysulfides ( where n = 2… 9…) are used for steel bluing. Calcium and barium polysulfides are used in pest control in agriculture. I do not think farmers keep it in the refrigerator.

[Edited on 24-2-2021 by vano]

[Edited on 24-2-2021 by vano]

vano - 24-2-2021 at 06:52

Quote: Originally posted by Sulaiman

Quote: Originally posted by vano

... It has white colour, it think it is very pure and particles are very small...

have you tried melting some (m.p. 115.2 ^oC) ?

Yes. These balls shine like pearls.

Bedlasky - 24-2-2021 at 08:39

Quote: Originally posted by vano

Quote: Originally posted by Bedlasky

Toluene is quite cheap and common chemical.

Polysulfides aren't form - they are unstable at room temperature, if you want to produce polysulfane oil, you must work below 0°C.

Sorry, I meant polysulfanes, not polysulfides. Polysulfides are formed, when you dissolve sulfur in NaOH, of course. But after acidification just sulfane is released, polysulfanes are unstable at room temperature.

vano - 24-2-2021 at 09:05

Quote: Originally posted by Bedlasky

Ok, no problem. Yes i agree with you that polysulfanes are unstable at room temperature. But i think small amounts of low molecular weight can be produced, very very small amount.

RogueRose - 24-2-2021 at 17:49

Quote: Originally posted by Bedlasky

Toluene is quite cheap and common chemical.

Toluene is getting MUCH more difficult to find as the 4-5 places I used to see it stocked, only 1 still sells it and the other products like lacquer thinner or paint thinner/remover seems to have moved away from using this for some reason. I'd gladly use a safer method other then heating toluene!

I've tried dissolving sulfur in toluene and found it does a very poor job at regular room temp, I think I got maybe 20-25 grams per liter. It does do a fairly good job when heated (still not very high - maybe 120-150g/liter), but I think it needs to get very close to it's BP to dissolve good amounts and that gets a little dangerous. I had this ignite one time and I'll tell you I've never seen so much soot produced in ~10 seconds as it left a THICK cloud floating strands of carbon and a huge soot mark above where it was being heated (5-6ft diameter). This was such a mess and I'm still not 100% sure how it started as I didn't have the power up very high on the heating element - but I guess it was hot enough to reach flash point..

Bedlasky - 24-2-2021 at 22:00

Quote: Originally posted by RogueRose

Quote: Originally posted by Bedlasky

Toluene is quite cheap and common chemical.

I am not saying that Vano's method is bad, it's interesting alternative which I never thought about. I am talking from my experience, because in my country isn't problem to buy some technical grade toluene and it's cheap. But I can imagine, that in other countries situation may be different. I agree that big advantage of Vano's method is, that you don't need to heat flammable solvent.

vano - 25-2-2021 at 05:07

In some places toluene is not sold at all, but these reagents are available in all countries, and I did not spend anything on these reagents, I received 1 kg of sulfur and 500 grams of citric acid as a gift, because it is already very cheap. I have sodium hydroxide granules, and in this reaction I used old hydroxide, which was looks like rocks. Plus the problem is the poisonous gases, and the smell of hydrogen sulfide is very strong, but for me it is not a problem, although I know it is bog problem in many countries.

Vomaturge - 25-2-2021 at 05:30

Quote: Originally posted by RogueRose

Quote: Originally posted by Bedlasky

Toluene is quite cheap and common chemical.

I think the flash point is 6C. It probably got just hot enough to flood vapors over the side of the vessel, and then they were ignited by static or electrical contacts in your heat source,

ChemTalk - 25-2-2021 at 20:59

Vomaturge - we just subscribed to your youtube channel. Looking forward to the chemistry videos!

unionised - 26-2-2021 at 05:01

Quote: Originally posted by RogueRose

but I guess it was hot enough to reach flash point..

The flash point of toluene is about 4 ^oC.

Once you are above the flash point there's enough vapour to produce a flammable cloud.
A spark from the thermostat or the stirrer is a plausible guess as the ignition source.

pneumatician - 2-3-2021 at 17:12

wow, you now, after some centuries, know what is Lac Sulphuris! :-) in vulgo english, milk of sulphur. De res.

macckone - 5-3-2021 at 08:34

It would seem other acids like vinegar (obviously purified to remove other organics) would work.
Citric acid is commonly available as food grade for use in baking, so using different acids is not an issue.