Ba(ClO3)2
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Sodium sulphite and sulphide from sulphur and NaOH
When conc sodium hydroxide solution is boiled with sulphur, a solution of sodium sulphide, sodium polysulphides and sodium sulphite is formed.
3 S + 6 NaOH = 2 Na2S + Na2SO3 + 3 H2O
Na2S + S ==> Na2S2 Na2S + 2 S ==> Na2S3
I was wondering how one might go about separating and purifiying the sodium sulphite and sodium sulphide from the final reaction mix.
I believe sodium sulphite has much lower solubility in water at near freezing temperatures. So perhaps most of the sodium sulphite could be
crystallized out by strongly cooling the solution.
As for the sodium sulphide, I have no idea how it could be separated from the polysulfides and any sulphite that didn't crystallize out.
So my questions are:
1. Is my idea on separating the sulphite by cooling the end solution likely to work?
2. How can I separate the sodium sulphide (free of polysulphides) from the end solution?
For the reaction, I assume using an excess of sodium hydroxide would be best to prevent lots of polysulfide forming.
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AJKOER
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Per one source (see http://m.jes.ecsdl.org/content/131/7/1545.abstract ) to quote:
"Chemical reactions of sulfur compounds have been studied in equimolar S-H2O melt at 100° C by voltammetry and UV spectrophotometry.
Disproportionation of sulfur is fast and quantitative according to
S8 + 6 OH- → 2 S3 (2-) + S2O3 (2-) + 3 H2O
On the contrary, addition of sulfur to sulfide is not quantitative and gives S2 (2-)...."
which suggests that the reaction of NaOH with S at 100° C is possibly even more complicated than your cited reaction indicates.
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Ba(ClO3)2
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Thanks for the response .
That's very odd, the article claims thiosulphate is also produced.
I just found a patent describing exactly what I hoped to achieve https://www.google.com/patents/US2705187
The patent suggests that sulphides, polysulphides and sulphites are the only products.
So perhaps the reactions between sodium hydroxide and sulphur produce purely sulphide, polysulphide and sulphite only when an aqueous medium is
present. After all, the paper you linked to described the reactions when the sodium hydroxide and sulphur are melted together without water.
I just really hope I can find a way to produce get sulphite and sulphide from the reaction(s). That patent would certainly be a good start, I just
don't know if the information it presents is accurate or not.
[Edited on 11-10-2016 by Ba(ClO3)2]
[Edited on 11-10-2016 by Ba(ClO3)2]
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AJKOER
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The caption on that article is:
"Sulfur Chemistry in Equimolar NaOH ‐ H 2 O Melt
II . Chemical Reactions Between Sulfur, Sulfide, Polysulfides, and Oxyanions"
Authors....
So, there is some water which does not support your comment of the reactions proceeding when the sodium hydroxide and sulphur are melted together
without water. Note also that the cited reaction temperature is 100 C (and not higher) and the reaction products include water.
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If the goal is a sulfide, a problematic alternative could be to pass a source of H2S over a target metal hydroxide while avoiding to employ an excess
of the toxic hydrogen sulfide (so as not form any H2S2) and stirring to address any local concentrations.
[Edited on 11-10-2016 by AJKOER]
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Ba(ClO3)2
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Oh sorry, don't know how I missed that. I made another mistake as well. The patent I linked to actually says quite clearly near the beginning that
thiosulphate is also formed. So I don`t see why the article you linked to causes any problems. If I were to follow the patent, do you think I would
end up with fairly pure sulphide and sulphite?
It seems to me that with an excess of sulphur everything gets a lot more complex. With an excess of hydroxide, possibly the products can be limited
somewhat to mainly just sulphide and sulphite.
I am aware of the method for making sulphides from H2S. However using sulphur and sodium hydroxide would certainly be a lot safer, and not necessary
all the hard if the patent is accurate.
[Edited on 12-10-2016 by Ba(ClO3)2]
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