Sciencemadness Discussion Board

Reducing Sodium Sulfate to its Sulfite

rstar - 29-9-2011 at 02:45

Hi Science geeks,

I need Sodium Sulfite in some of my experiments as a reducing agent, and i don't have it.

I have Sodium sulfate, but can anyone tell me how to reduce it to Sulfite ??

Thanx in advance for any help :D

hissingnoise - 29-9-2011 at 03:14

Na<sub>2</sub>SO<sub>3</sub> is conveniently prepared by reaction of the carbonate with H<sub>2</sub>SO<sub>3</sub> or by reaction of hydroxide with SO<sub>2</sub>.


rstar - 29-9-2011 at 03:42

@hissingnoise
But I don't have any H2SO3 or any gas tube for passing SO2 gas at this time. :(

ScienceSquirrel - 29-9-2011 at 03:47

Sulphite is a lot easier to reduce than sulphate so you will not form sulphite by reducing sulphate, you will end up with sulphide.
Go down your local home brew shop and buy some sodium metabisulphite, problem solved! :)

rstar - 29-9-2011 at 04:43

@ScienceSquirrel
Thanx for the tip

blogfast25 - 29-9-2011 at 05:14

Yes to metabisulphite: much more OTC than sulphite and for most purposes just as good... A bit overlooked by many a hobbyist, I feel...

ScienceSquirrel - 29-9-2011 at 05:23

If you want the suphite, just add sodium hydroxide in the calculated amount to a solution of the metabisulphite.
I suspect that reaction of sodium metabisulphite with sodium nitrite could be a good almost OTC route to disodium nitrosodisulfonate and then to Fremy's salt.

[Edited on 29-9-2011 by ScienceSquirrel]

rstar - 29-9-2011 at 05:28

What would happen if Na2SO4 is reacted with elementary Sulfur?? Will it be Reduced ??

sternman318 - 29-9-2011 at 07:42

Quote: Originally posted by ScienceSquirrel  
Sulphite is a lot easier to reduce than sulphate so you will not form sulphite by reducing sulphate, you will end up with sulphide.
Go down your local home brew shop and buy some sodium metabisulphite, problem solved! :)


Some 'stump removers' are composed of sodium metabisulfite ( Bonide brand from Home Depot)

ScienceSquirrel - 29-9-2011 at 07:45

Quote: Originally posted by rstar  
What would happen if Na2SO4 is reacted with elementary Sulfur?? Will it be Reduced ??


I doubt sodium sulphate would react with sulphur.
Sodium sulphite boiled with sulphur forms sodium thiosulphate.

Mr. Wizard - 29-9-2011 at 08:26

Wouldn't burning sulfur in air produce SO2 that could be pulled through water to form a H2SO3 solution? This solution of could be reacted with sodium carbonate or sodium bicarbonate to produce sodium sulfite, releasing the weaker acid CO2. The SO2 could be drawn directly through a solution of Na2CO3. Is there a reason why the more expensive and dangerous NaOH would be used? I see hissingnoise has recommended the same thing already.