Re: Sodium Bisulfite

There is also sodium sulfite that works as sodium bisulfite according to
James book.
But I was told that the sulfite does not create the solution acid and
therefore the cromium component becomes insoluble cromium.
What does this mean in terms of stains I don't know.
Can anybody help?
Thanks
Giovanni
----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Tuesday, October 05, 2004 8:15 AM
Subject: Re: Sodium Bisulfite

> This goes clear back to a discussion we were having in August about
> whether there is a difference between sodium bisulfite and potassium
> metabisulfite. I thought I had seen a difference between sodium
> bisulfite and sodium metabisulfite, but later came to the conclusion,
> (quoted below) that the batch of sodium metabisulfite I had made my
> observations on may not have not a good batch, it probably had got some
> water in it.
>
> More recently, I needed more sodium bisulfite and while ordering it, I
> ordered some potassium metabisulfite, just for a comparison. I could see
> no difference between the potassium metabisulfite and the sodium
> bisulfite, either in strength of odor or in clearing effectiveness at
> the same concentration. This seems to support my earlier belief that
> there was something wrong with the sodium metabisulfite I had used
> before, (Na or K is irrelevant) and also supports the statements from
> chemists in that thread saying that the different forms of bisulfite are
> functionally equivalent. I didn't test whether there was a difference in
> how much they softened the gum, but given that chemists seem to agree
> that all the bisulfites are essentially the same functionally, I would
> suspect that the belief that sodium bisulfite softens the gum more than
> potassium metabisulfite is just another of those myths.
>
> Katharine Thayer
>
>
>
> Katharine Thayer wrote:
> >
> > So here's what I understand from the chemists:
> >
> > All the sulfites are basically the same functionally, and should work
> > the same at roughly the same concentration, and should smell the same,
> > unless the pH is different.
> >
> > My experience with sodium metabisulfite is based on one batch only; I
> > found it more difficult to dissolve than sodium bisulfite because of the
> > "plates" or wafers that it formed, and it was ineffective at 5%; I had
> > to mix it at many times 5% to get any clearing effect. (And "freely
> > soluble" seems right; I put the entire 100 g into maybe 500 ml water.)
> > And while its smell was similar in quality to that of sodium bisulfite,
> > it differed in intensity; the fumes didn't knock me over and make me
> > cough like the fumes of sodium bisulfite. So what is the meaning of all
> > that, if the two things should be equivalent? The dry material came in a
> > sealed plastic bag and I kept it sealed until I mixed it, but I'm
> > beginning to think, on the basis of what I'm hearing, that there was
> > something wrong with my batch.
> >
> > Specifically, I'm thinking that perhaps some water got into the material
> > (the way the stuff was in wafers instead of powder sort of suggests
> > that) and rendered it less effective by oxidizing it to sulfate. (I
> > haven't had that happen with sodium bisulfite). So I'm retracting any
> > statement I've made here about the difference I've observed between the
> > sodium bisulfite and metabisulfite; I think that observed difference was
> > probably spurious and not useful to the discussion.
> >
>
Received on Wed Oct 6 12:48:27 2004