[ihatemyalarmclock]

We used it in photo developing.

Are you sure you aren't referring to "sodium thiosulfate?"

In a b/w darkroom, it was commonly called "fixer."

It smelled sour, but not nearly as bad as "rotten eggs."

[spunkets]

Sodiun thiosulfate is used as a reducing agent in photo developing. Sulfides are not.