Sciencemadness Discussion Board

Sodium Metabisulfite Mystery

APO - 10-5-2013 at 00:36

I heard on here that Sodium Metabisulfite decomposes to Sodium Oxide and Sulfur Dioxide on Heating. I could not find anything else on this, so I tried to test it. I added some Sodium Metabisulfite to a skillet and set it to high heat. There was definitely loads of Sulfur Dioxide being evolved, and when I added water there was a lot of initial bubbling (probably cause it was still hot) and then it started etching away at the skillet's non-stick coating. I didn't have anything on hand to test the pH of the solution, can anyone else please test this?

Here is the only balanced equation I could come up with:

Na2S2O5 = Na2O + 2SO2

unionised - 10-5-2013 at 12:28

How about
Na2S2O5 --> Na2SO3 + SO2
?
(Which is about a zillion times more likely)

Acidum - 10-5-2013 at 12:30

I know that potassium metabisulfite decomposes to SO2 and K2SO3 at around 200oC, and that both (Na and K metabisulphite) release SO2 with acids.

If You are looking at wikipedia as starting point (which in some time you will realise is bad thing) than try to follow its reference...takes you to page with no such information.

Just check pH with universal indicator strip.

blogfast25 - 10-5-2013 at 12:57

Quote: Originally posted by APO  
I heard on here that Sodium Metabisulfite decomposes to Sodium Oxide and Sulfur Dioxide on Heating.


Here? It wouldn't be the first time there some misinformation on this board.

Sodium metabisulphite decomposes to sulphite. Sulphite itself would only start decomposing at insanely high temperatures and it's not clear what it would result in.

There are no easy ways to prepare Na2O.

[Edited on 10-5-2013 by blogfast25]

APO - 10-5-2013 at 16:00

Thanks guys.