Quote Originally Posted by Ian Grant View Post
Sodium Metabisulphite is often used in small quantities
in developer formulae.
The importance of the metabisuphite is the free SO2 it gives off,
it's often used to stabilise commercial powdered developer -
used in Part A with the developing agents. Ian
SO2, sulfur dioxide, a gas. A bisulfite when moist, as it may
become with powdered commercial developers, acts like any
sulfite to preserve. Why the BIsulfite is still a mystery. Free
sulfur dioxide, sulfite or bisulfite, is unlikely because it
would take quite an acidic environment to cause it's
release. Over acidic stop baths can cause it's
release. Dan