Making sulphite from Metabisulphite?

[Athiril]

I saw a thread on photo.net some time ago referencing making Sodium Sulphite from Sodium Metabilsulphite and Sodium Hydroxide from APUG.

Searching for sulfite oh here and with other terms brings up so many threads its lkike a needle in a haystack which I cant sit on..

I wanted to know if that actually is that case of making sulphite from metabisulpite, and if the same thing can be done with potassium metabisulphite and sodium hydroxide (or would I need to hunt down potassium hydroxide)

edit: okay finally managed to find one - (there was a url link here which no longer exists)



But still trying to find how much hydroxide to how much metabisulphite i should use in how much water etc.


Also I think a sticky with links to threads/page numbers on threads detailing chemical conversions would be useful.


edit: frustrated I used google's search specifying site:apug.org which was much easier to find info with.
(there was a url link here which no longer exists)

 

[Alan Johnson]

Can you say specifically what metabisulfite and hydroxide you want to start with,then it should be possible to calculate.

 

[Athiril]

I have both potassium and sodium metabisulfite, and only sodium, hydroxide.

Theyre all basically pure.. to a technical grade at least.

 

[Alan Johnson]

From the molecular weights:
Na2S2O5 + 2NaOH -> 2Na2SO3 + H2O
190.1g....+..80g....-> 2x126.04g (=252.08g) +...
If you want to make a solution containing say 70g/L sodium sulfite everthing has to be multiplied by 70/252.08,ie dissolve in 1L COLD water:
52.79g sodium metabisulfite and 22.21g sodium hydroxide.
Sodium hydroxide is hazardous,it also gives out heat on solution.
www.ccohs.ca/oshanswers/chemicals/chem_profiles/sodium_hydroxide/
Sodium metabisulfite is strongly acidic,reacting with hydroxide gives out heat.
Therefore protective gear including goggles should be worn and due attention given to safety.In particular do not make strong solutions which may boil.IDK the concentrations at which this occurs so take care.
If you mix potassium metabisulfite and sodium hydroxide in the molecular proportions there will result a stange mixture of sodium and potassium sulfites that nobody ever uses,I would not go there.

 

[Athiril]

Okay cheers!

 

[Lowell Huff]

We will ship to Australia, the chemicals you need. askus@claytonchem.com