Quote Originally Posted by Rudeofus View Post
If you look at the numbers, you'll see that Salicylic chelates FeII better than Citrate (6.55 vs. 3.2), and it also chelates FeIII better than Citrate (16.35 vs. 11.85). If you have Salicylic Acid in your dev, you won't need Citric Acid any more. Note that chelate stability does not tell the whole story since EDTA, which is a strong chelating agent for both FeII and FeIII, is known to accelerate the Fenton reaction.
My goof! I swapped the FeII and FeIII numbers for Salicylic. So you're right; Salicylic beats Citric for both types of Fe ions.

I've heard before that EDTA accelerates the Fenton reaction, and that this is why Kodak uses DTPA in XTOL instead. But here's a report saying that DTPA also accelerates the Fenton reaction:

From http://www.efchemicalconsulting.co.u...cal-damage.pdf
other aminocarboxylate chelating agents such as NTA
(nitrilotriacetic acid) and DTPA, in addition to EDTA,[7] all greatly accelerate the
Fenton reaction.

My question is: Has anyone verified that EDTA indeed destroys ascorbate developers? Or is this a hypothesis based on studies not related to developers?

Mark Overton