Thank you, everyone, for your ideas.
Rudi, it sounds like sodium sulfite is doing more work than just being a "simple" wash-aid which helps to liberate thiosulfate from paper fibres, sizing etc. I have always thought it had to be more active, after all, it is a known grain solvent when used as part of some film developers. Thank you for sharing the suggestions, I share your curiosity as to that it may convert insoluble complexes to soluble ones, or that it may desorb them from the grain crystal. I would love to know if others support this line of thinking.
Originally Posted by Rudeofus
Ian, if there is a chance you find that diagram, I'd be interested to learn from it. I am curious about the equilibrium process when sodium sulfite is part of it. Thank you for sharing your other thoughts, too.
Originally Posted by Ian Grant
Gerald, this is a very reasonable suggestion, and one which seems to agree with the common sense of today, and one which I follow in my process, wholeheartedly. May I, however, politely ask you, as a chemist, if you have a justification for this otherwise very sensible suggestion, other than based on your feelings and the reason of fixer being not that expensive? For example, would you say that a two-bath fixer regime offered significant advantages to a regime that used only 1 fixer, and which showed through test results that there are no residual thio (silver nitrate test) and no residual silver halides (sodium sulfide test)? For argument's sake, assuming the paper was fixed in a single bath of a neutral ammonium thiosulfate fixer containing no more than between 0.5–2g silver/l, with no significant amount of iodide, for 1 minute, followed by a brief water rinse, and a 3 min 2% fresh sodium sulfite bath, plus a wash of 1 hour, all at 20C (68F)? I can certainly see the safety net that a 2nd fix can provide in case the first one goes significantly over 2g/l, but what other reasons would be there? I am simply trying to find out if the action of sodium sulfite is far more important than we have been assuming it to be.
Originally Posted by Gerald C Koch
John_S, thanks for posting the comments by Ryuji, but I am concerned that his article has been posted here with his permission. If not, would it be better, perhaps, if you posted only a relevant extract, rather than the entire article? Many thanks for your kind help, I do not want to upset anyone.