Sodium sulfite - chemical commonly used as a preservative in many developing solutions.
Sodium thiocyanate - alternative to potassium thiocyanate and is used as a silver solvent in physical and ultra-fine grain formulae.
Metol 12.0 g
Sodium sulfite, anhydrous 37.6 g
Sodium carbonate monohydrate 41.0 g
Sodium bromide 4.8 g ...
Sodium sulfite is the preservative most commonly used in developing solutions. ACCELERATOR All developing agents (not developing solutions) are either neutral or slightly acid.
The other way to do it is to combine selenium with sodium sulfite to produce sodium slenosulfate. Effectively sulfur combined with sodium sulfite makes sodium thiosulfate which is why fixer is stabilized by additing sodium sulfite.
-Preservative - chemical, commonly sodium sulfite, used in developing solutions to prevent rapid oxidation of the reducing agents in use.
The development action which occurs in processing "lith" materials. The oxidation of hydroquinone produces new and highly active reducing agents, semiquinones, in the presence of a low quantity of sodium sulfite.
 See also: Processing, Development, Oxidation, Photograph, Silver
  
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