Ehrrmmmm... I realise that that post was a lot easier to write than to readOriginally Posted by ann
What happens is this: The sulfite dissolves the sulfur film on the print, turning into thiosulfate in the process.
When sulfite gets into the toner, it again turns into thiosulfate and dissolves the sulfur ("milky").
So the print tones a bit differently, since there's now fixer in the Viradon as well! Then after a while it stops working, because all the sulfide is used up or turned to thiosulfate. Prints don't tone too well in fixer
Sulfite is a "magical" stuff - it absobs sulfur (turning to thiosulfate) and oxygen (turning to sulfate) both. Sulfate has very little use in photography, but thiosulfate is useful for dissolving silver halides ("fixing"). It also dissolves silver a little bit (or at least makes it easier for it to dissolve), so it helps to speed up some reactions - like sulfide toning and the iron/silver reaction in van Dyke prints.
Still confused? You're not alone!