Bisulfit or meta bisulfite

[herb]

I was getting ready to mix up some hypo clearing agent, and discovered I do not have bisulfite, only metabisulfite. Can I use that? the recipe is
200g of sodium sulfite I have plenty of that
15g of sodium bisulfite, ?this is where I would make the substitution.


cold water to make 1 liter.

Many thanks to the chemists among us.

 

[srs5694]

See (there was a url link here which no longer exists)

 

[Ian Grant]

There was a long thread about this a few weeks ago. While they are actually different Sodium Bisulphite is unstable as a powder, what's sold as Bisulphite is a mixture of Bisulphite and Metabisulphite. In solution they are the same.

So yes you can use Metabisulphite, but plain sulphite is fine on it's own as hypo clear.

Ian

 

[herb]

Metabisulfite

Many thanks. I must have been out of town when the thread was made-I am always impressed with the knowledge there is in this group.

 

[dancqu]

Sodium Bisulphite is unstable as a powder,
what's sold as Bisulphite is a mixture of Bisulphite
and Metabisulphite. In solution they are the same. Ian

One molecule of metabisulfite plus one molecule water
equals two molecules of bisulfite. The bisulfite is the
fully hydrated form.

As sulfites the two can be oxidized to the sulfate.
In use for years, I've not had any indication of that
with my well sealed supply of bisulfite. Also, it shows
no signs of caking. With use as an hca, it's solution
has short life. Dan