Sodium Sulfite

[John Lockhart]

Most fixer formulas that use sodium thiosulfate also specify some amount of sodium sulfite as a part of the formula. What is the role of sodium sulfite in the fixer?

Sorry for asking what may be a really basic question, but I couldn't not find a straight answer on the web.

 

[donbga]

Most fixer formulas that use sodium thiosulfate also specify some amount of sodium sulfite as a part of the formula. What is the role of sodium sulfite in the fixer?

Sorry for asking what may be a really basic question, but I couldn't not find a straight answer on the web.

Sodium sulfite is typically used in conjunction with an organic acid in acidic fixer formulas which will produce a sulphurous acid in solution. Sulphurous acid doesn't decompose the thiosulfate. Sodium bisulfite maybe used instead of sodium sulfite.

I think homemade fixers are less expensive than store bought but volume purchases of constituent chemicals are usually called for to make really worth doing. Even so, fixer is usually the most expensive component of processing B&W paper and film and using fixers one shot is wasteful.

Don

 

[RalphLambrecht]

Sodium sulfite is used with acid fixers to prevent an accumulation of sulfur, due to a reaction of thiosulfate with acids. It quickly reacts with colloidal sulfur and creates fresh sodium thiosulfate.