Fixer: What does the dissolving?

[Doremus Scudder]

Actually, the thiosulfates in the fixer react with the silver halides left in the emulsion and, through a number of reactions (which become less effective with dissolved silver building up in the fixer) render those former-silver-halides water soluble. In the end, it's the water that does the dissolving.

Best,

Doremus

[nmp]

Water is the person pushing the cart made up of sodium thiosulfate and the cargo is silver halides.

[Ulophot]

Thanks, all. I think I had assumed that sodium or ammonium thiosulfate was the acid that was doing the work (did I mention may masterful command of chemical knowledge?), and therefore that something had been substituted for it in the low-acidity fixers such as TF-5.