[pure-silver] Re: Chemical subsitution

In solution they are the same thing.  I believe that you can use about the
same mass of either compound.

Jurgen


On Thu, 26 Apr 2007 18:25:43 -0700 (PDT), Eric Nelson wrote
> I have discovered that I am out of sodium bisulfite
> and need to make some HCA tonight for prints I just
> finished.
> I have tons of sodium metabisulfite and have looked
> through the archives to see if this compound is
> specifically addressed as an AKA or substitute
> compound for sodium bisulfite.
> I've included some quotes below of Richard's that seem
> to answer this question, so I'm wondering if there is
> a definitive answer out there as to whether I can use
> metabisulfite in place of bisulfite gram for gram in
> the HCA formula or at what ratio it would need to be
> at.
> 
> I'm a cook not a chef so molar aspects of these
> compounds and the Avogadro's number will go over my
> head. ;-)
> And what the heck is bisulfite lye?  Found that
> mentioned in one of my search results.
> Eric
> 
>  "Long ago there was a discussion of what exactly was
> meant 
> by sodium bisulfite in Kodak and other formulas. It
> appears 
> that the compound is actually metabisulfite, or mostly
> so. 
> Sodium metabisulfite is much less expensive than real
> sodium 
> sulfite and is certainly suitable for this formula."
> 
> ."various MSDS list either Sodium Bisulfite or
> > Sodium Metabisulfite.
> > > Kodak 
> > > Sodium Bisulfite appears to be mostly the
> > metabisulfite. Evidently it
> > > does 
> > > not matter which is used.
> > > Because the formula is not published the amount of
> > EDTA and Citrate are
> > > not 
> > > firmly established. The MSDS for the concentrate
> > (powder) lists the
> > > amount 
> > > of either as 1 to 5% by weight. It disappears from
> > the working solution. 
> > > It's possible the amount in the stock should be
> > only 1 gram of each but I 
> > > think from Haist or somewhere I got the idea that
> > it should be more. 
> > > Perhaps a compromise of 2 grams each should be
> > used.
> > > I think 15 grams of the bisulfite/metabisulfite is
> > correct. In any case
> > > the 
> > > target pH is 7.0"
> 
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