Patrick, there's something nagging away in my mind about Metabisulphite. Yes the early Rodinal type formulae used it & Hyroxide to form Sulphite, at one point that was the best way of producing the Sulpite in solution.

We've had this discussion before but there is also the subtle difference between Bisulpite & Metabisulpite, and last time I was in the UK I found a reference and short extract from a Kodak paper on the subject, which I posted here on APUG. Kodak Bisulpite is in fact a mixture of Bisulphite & mainly Metabisulphite, and Kodak were referring to the interchangeability of their Bisulphite with Metabisulphite. J.T Baker sell both forms in bulk.

At some point before WWII Agfa began using Sulphite, I think something else is happening as we also know that around then they were also adding anti-foggant.

The referance to Oxygen scavenger yesterdaym (Ammonium Bisulphite) was what triggered my thought, and knowing that Metabisulphite in a developer helps cut dichroic fog.

In the wine trade Metabisulpite solution is used as an anti-oxidant, and steriliser as it's more powerful than Bisulphite, but no-one seems to explain why satisfacorily, It has a lot to do with free SO2.

Ian