Quote Originally Posted by Gerald C Koch View Post
Hi Mark,

Iron forms a lavender/purple complex with salicylate ions. So it appears that the chelating agents are working. To answer your other question ferrous sulfate oxidizes fairly rapidly particularly in moist air. Ferrous ammonium sulfate is more stable but either should be OK.

I would be interested in what would happen without the chelating agents. Would be ascorbate ion be rapidly destroyed at the concentrations you used. Also the longevity of your developer with the chelating agents and iron and copper present.

Hi Jerry, here's a surprise: Yesterday's brew had no chelating agents! I guess I didn't make that clear, but I wanted to see whether it would die quickly with no protection against Fe/Cu ions. Thanks for the note about oxidation of ferrous sulfate. I transferred it to a little amber glass bottle last night, so hopefully it'll keep a while. Anyway, do you know of anything else that would cause the purple? I used distilled water, so there should be no unknown chemicals in there.

Mark Overton