YT2095
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Sulphite to Thiosulphate
I`m going to try and produce sodium Thiosulphate, I can make the sodium sulphite by bubbling SO2 through NaOH soln, the next step according to it is
to boil elemental sulpher in this soln.
now the part I can`t figure is How that`s suposed to work, since the BP of the water and the MP of Sulpher are a little different.
does this need to be boiled under pressure?
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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not_important
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No, just add powdered sulfur, plenty of surface area to react.
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YT2095
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I can see how it would react if the soln was still basic with NaOH, that would then form polysulphide (soluble), I`ve always considered Sulpher as
insoluble in water.
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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garage chemist
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It does work with neutral sulphite solution, BUT you have to add a surfactant, like a drop of dishwashing detergent so that the solution wets the
sulfur. Otherweise there will be no reaction unless you work under pressure and heat the water to above the melting point of sulfur.
One of the students in my course had to do the preparation of sodium thiosulfate with the detergent method.
You also have to protect the solution from oxygen.
You cant simply make sodium sulphite from SO2 and NaOH. You either have to add SO2 to a specific pH or first saturate NaOH solution with SO2 and then
add an equivalent of NaOH so that the formed sodium hydrogen sulfite reacts to sulfite.
The easiest way would be to buy sodium metabisulfite and mix it with one mol NaOH solution.
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YT2095
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that makes sense, I already have the Metabisulphite and also the Thiosulphate, and I know I could buy either at a photography shop easily.
but there`s no Fun or Challenge that way, and I would miss the experience and learning, it`s nice to know how everyday things we use and take for
granted are Made 
I was concerned about the Oxygen also, converting it to plain sodium sulphate, esp with my SO2 method, it relies on burning Sulpher on a spoon in a
combustion flask being fed air via a small pump and the gases being used from there.
that detergent idea is Genius! the powdered sulpher I have tends to float and/or make little balls with trapped air that float also, and the
crystaline form would lack the surface area.
I know there will be impurities, but I don`t mind a little extra metabisulphite as that`s a stabiliser against oxidation of the thio, and the sulphate
would be totally ignored in the developer/fixer soln.
Thanks
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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hashashan
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i made thiosulfate from sulfite once, its quite easy however a time consuming operation.
you need to wet the Sulfur with alcohol(this way it gets mixed with the water. Bring the Sulfite solution to boiling point and then start adding the
Sulfur in small portions while mixing like hell, add the next portion only after the first dissolved.
You can also just dump in all the sulfur and reflux the mix for several hours(or just boil and add water from time to time). thats it.
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woelen
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If you use the solution for fixing purposes, then be ABSOLUTELY sure that there is no free hydroxide in solution. Such solutions lead to formation of
sulfide, and even trace amounts of sulfide in a fixer solution are a 100% disaster and a 100% guarantee that the prints come out all black/dark brown.
In the presence of hydroxide, sulphur is disproportionated to sulfide and sulfite. The sulfite may take up more sulphur, forming thiosulfate and the
sulfide takes up sulphur, making polysulfide.
A not yet fixed print contains AgBr/AgCl/AgI and the image is present as Ag. The fixer takes out these salts as follows (for AgI and AgCl it is
similar):
AgBr(s) + 2S2O3(2-) ---> [Ag(S2O3)2](3-) + Br(-)
A complex is formed.
Even trace amounts of sulfide prevent formation of this complex, but the extremely insoluble Ag2S is formed instead:
2AgBr + S(2-) --> Ag2S + 2Br(-)
The latter reaction is used sometimes in the process of sepia toning: A thoroughly fixed print (which has no Ag(+) anymore, only Ag) is immersed in a
bath, containing both a mild oxidizer and potassium bromide. The Ag-metal is oxidized to Ag(+) and is precipitated in turn as AgBr. The Ag-particles
are replaced by AgBr particles, at the place where the image resides. This oxidation process fades away the image. As oxidizer, the mild oxidant red
prussiate of potash is used, but many other soluble mild oxidants are suitable.
Next, the print is rinsed well, to get rid of the oxidizing solution, while keeping the AgBr, and then it is immersed in a solution, containing
sulfide ions. The pale yellow/brown AgBr then is replaced by dark brown Ag2S and the image returns again, now with a brown/sepia hue. Polysulfides can
be used instead to make a deeper brown, even chocolate brown is possible.
[Edited on 4-7-07 by woelen]
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YT2095
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Fantastic! Thank You
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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Aqua_Fortis_100%
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Taking again this thread from the ground 
Very interesting that alcohol/surfactant trick to help dissolving sulfur as well protecting the solution from air.. Unfortunately the inorganic prep.
books I have see didnt say anything about.
A very good prep. since here is very hard to find any OTC thiosulfate.
Yesterday I added some Na2CO3 to sodium metabisulfite until foam subsided and then, added a small pinch of more metabisulfite just to get things
slight acidic.. Hoping that works 
BTW, all of you know that the finer the sulfur, the better.. But are that good for that task the usual sulfur brands found in pharmacies (all saying
"'sublimed' sulfur flowers" on the label) ?
If not, is there any trick that I can do to turn that even more fine? (I still dont have my own ball mill  )
[Edited on 5-9-2008 by Aqua_Fortis_100%]
"The secret of freedom lies in educating people, whereas the secret of tyranny is in keeping them ignorant."
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ScienceSquirrel
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Have you tried having a 'fish' around your local pet fish shop.
Round here it is sold as a dechlorinating agent for tap water.
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