[pure-silver] Re: sulfite in PMK working solution
- From: Sandy King <sanking@xxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Tue, 28 Dec 2004 18:04:14 -0500
I am actually using sodium metabisulfite in my tests, not sodium bisulfite.
Would it be fair to say that one should substitute for the
metabisulfite (assuming that the label is accurate) at the rate of
one part metabisulfite to two parts sulfite?
I would also conclude that it is probably not possible to know at
this point exactly what Hutchings used in the original formulation,
i.e. 1) pure sodium bisulfite, 2) a mixture of bisulfite and
metabisulfite, or 3) pure metabisulfite sold as bisulfite?
Sandy
>This depends on the precise nature of the "sodium bisulfite" used in
>the solution. Pure sodium bisulfite in dry form is exceedingly rare
>unless you pay a lot of money for analytical reagent grade chemical.
>Most are mixture of bisulfite and metabisulfite, or simply
>pure metabisulfite sold as bisulfite.
>
>1 mole of bisulfite makes 1 mole of sulfite when pH is adjusted well
>above its pK. Similarly, 1 mole of metabisulfite makes 2 moles of
>sulfite. (This is because 1 mole of metabisulfite makes 2 moles of
>bisulfite when fully dissolved in water.) These are precise.
>
>What is not precise is what the label says and what exactly it is.
>--
>Ryuji Suzuki
>"Keep a good head and always carry a light camera."
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