Re: Sodium Bisulfite

Hi Martin,
If so, where does it stand the sodium sulfite?
Christopher James book says it can be used as a replacement of sodium
bisulfite, also photformulary.
Thanks,
Giovanni

----- Original Message -----
Wrom: NNYCGPKYLEJGDGVCJVTLBXFGGMEPYOQKEDOTWFAOBUZ
To: <alt-photo-process-l@sask.usask.ca>
Sent: Thursday, August 26, 2004 12:32 AM
Subject: Re: Sodium Bisulfite

> Here's the math:
>
> Formula weights are potassium metabisulfite=222, sodium metabisulfite=190,
> sodium bisulfite=104. Remember that you get two bisulfites from every
> metabisulfite. There was no listing for potassium bisulfite.
>
> A 5% solution of sodium bisulfite=0.48M The equivalent molar
concentrations
> are 5.33% potassium metabisulfite and 4.56% bisulfite. All are close
enough
> for 5% to work in clearing baths for most situations.
>
> The potassium salts are listed as pharmaceutical antioxidants, and the
> potassium salt as the food additive, and wine preservative (there may be a
> cost-effective opportunity for bulk purchases here). The metabisulfites
are
> listed as "freely soluble" in water. The sodium bisulfite is listed as
> soluble in 3.5 parts water (~30% solution). pH may affect the ability to
> dissolve.
>
> All are listed as giving off a sulfur dioxide odor. They pick up water
from
> the air, and oxidize to sulfate (and are then ineffective). Keep them dry
> and tightly closed. As far as the smell of a solution goes, check the pH.
> A solution is acidic. The acid form is volatile, and therefore smelly.
Get
> some test strips or an inexpensive meter. I don't know the ideal pH.
With
> bulk and technical grades, this may be the source for differences from
type
> and batch differences. Remember, the difference between a bisulfite
> solution, and a sulfite solution (as in developer) is just the pH.
>
>
> ----- Original Message -----
> Wrom: XUWLSZLKBRNVWWCUFPEGAUTFJMVRESKPNKMBIPBAR
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Wednesday, August 25, 2004 1:51 PM
> Subject: Re: Sodium Bisulfite
>
>
> > Katharine Thayer wrote:
> > >
> >
> > >
> > > But the problem is that it's sodium bisulfite and *potassium*
> > > metabisulfite that are at issue in this discussion, so how similar are
> > > they? My chemist consultant says that he doesn't see a role for the
> > > potassium and sodium, so as far as he's concerned they are spectator
> > > ions in the reduction. If this is correct, then it's only the sulfite
> > > that matters, and metabisulfite should perform about the same
regardless
> > > of whether it came into solution along with potassium ions or sodium
> > > ions. If that's so, then why would we expect big differences in how
they
> > > perform in the clearing and washing process?
> > >
> >
> > I just re-read my chemist's message, and found that the conclusion I
> > came to by reasoning my way through a logical sequence, he actually
> > said straight out to start with: "I wouldn't think there would be any
> > difference between sodium and potassium
> > metabisulfites at the same molar concentration." So maybe I should just
> > read my mail more carefully and give my brain a rest. Any chemists
> > disagree with this, please say so, and support your answer. Thanks,
> >
> > kt
> >
>
>
Received on Thu Aug 26 07:47:38 2004