Don - I think you mean Ag+(aq) cations, not Na++ - Na++ doesn't exist in
normal water environment, only in vapour form!
Sodium metal is in group I of the Periodic table and can only form
Na+(aq) in a water environment as from e.g. NaCl solution.
Howard
Don Feinberg wrote:
If the film is processed correctly, there should be no silver remaining.
The ferric ammonium EDTA converts the silver to positive ions ("cations"),
Na++. The ammonium thiosulfate fixer converts the Na++ to a variety of
silver thiosulfate complexes, which get washed out in water.
If the film is properly fixed, all the silver will be gone.
The principle is the same for RA4 paper. RA4 blix is ferric ammonium EDTA
and ammonium thiosulfate. C41 "blix" is also based around ferric ammonium
EDTA and ammonium thiosulfate. The reason that many C41 kits use separate
C41 "bleach" and "fix" steps is that using a ferricyanide bleach is cheaper
than the ferric ammonium EDTA (but they are chemically antagonistic). It
doesn't cost the kit mfgr anthing more to do the extra 6 minute step!
