Quote Originally Posted by Photo Engineer View Post
Way back when, he said he was going to get a patent on his special chelating agent, but I have seen nothing in the literature yet. PE
He's been silent for months. I suspect he lost interest.

For nearly a year, I thought that (1) DTPA would not chelate iron, and (2) Kodak avoided the problem by using iron-free chemicals that we ordinary folks can't obtain. I was wrong. DTPA chelates iron. True, it's harder to find, but I think it's obtainable with effort. For example, SpectrumChemical.com (in Los Angeles) sells 25 grams of pure DTPA (not a salt) for $17 here. I remember a posting where somebody mixed XTOL from the patent. He had a hard time finding DTPA, but finally located some in New York (I think). Also, it's worth calling Photo Formulary, as they stock chemicals not on their website.

I mixed a new batch of XTOL a couple of days ago, storing it in five 1-litre bottles. And I thought of a way of making it last longer: Store the extra bottles in the refrigerator. Sulfite will precipitate out of solution, but when it's time to start a new bottle, warming and shaking it should bring the precipitate back into solution. Kirk Keys reminded me that chemical reactions proceed half as fast with each 10C temperature-drop, so refrigeration should make XTOL last around 1.5-2 years instead of 6 months. Is there any reason why this would not work?

Mark Overton