Rudeofus: then why with permanganic acid a metabisulfite clearing bath is used?
I ask myself: what's the purpouse of the clearing bath?
Is it to reduce CrVI to CrIII and to form Ag-sulfates complexes that are readily soluble in water?
Sodium sulfite is Na2SO3, sodium metabisulfite is Na2S2O5. Looking at their chemical formulas I see that metabisulfite anion has five negatively charged oxygens (three of which are more negatively charged than the other two), the same as the anion in sulfite.
So I guess the chemical reaction in bleach must be the same.