The patent makes a number of unique claims. The link is here: https://patentimages.storage.googleapis.com/93/a0/29/7c113f9b5953e1/US5264323.pdf
Overall interesting bits to me, specifically for lith developer formulation:
* Ascorbic acid + p-aminophenol (or a hydrazine developing agent) can produce something competitive with hydroquinone based lith developers
* A number of "known in the art" alternatives to the traditional formaldehyde-bisulfite complex. Most interesting one being "succinaldehyde bis-sodium bisulfite" which is hard to source and purify, but otherwise non-toxic both in the pure form and in the bisulfite salt form
* The most interesting and radical claim. If you include enough carbonate in the solution (>0.5 molar), it prevents oxidation by aeration (though of course does nothing for auto-oxidation), while also as expected provides a ton of buffer capacity
The last claim is especially crazy to me, given that more carbonate seems to accelerate oxidation, but I've never attempted to use such a strong solution of carbonate (basically near solubility limit). Applications could include: A stable solution of ascorbic acid in alkali, applying the same concept to hydroquinone (with a peroxide scavenger such as oxalate), a stable (non-lith) print developer could be produced using ascorbic acid + something superadditive (phenidone with lots of anti-fog?), and likely other applications.
My real question is do these concepts actually hold weight? The patent is such a late (90s) patent that it gives an excellent reference of prior art in the field, but these claims seem rather extreme to me, and completely unexplored in the home formulation game. Any chemists care to weigh in?
edit: The only developer I can think of to potentially exploit this effect is the legendary Ansco 130. It uses more carbonate in it's stock solution than the 0.5 molar threshold. It's longevity has always been upheld to be because of the use of glycin, but maybe the amount of carbonate and the fact that it's used as a stock or 1:1 solution (whereas most solutions like this would be diluted much further) is a bigger key. Creating a stable developer with so much carbonate in the working solution would definitely be a challenge regardless
Overall interesting bits to me, specifically for lith developer formulation:
* Ascorbic acid + p-aminophenol (or a hydrazine developing agent) can produce something competitive with hydroquinone based lith developers
* A number of "known in the art" alternatives to the traditional formaldehyde-bisulfite complex. Most interesting one being "succinaldehyde bis-sodium bisulfite" which is hard to source and purify, but otherwise non-toxic both in the pure form and in the bisulfite salt form
* The most interesting and radical claim. If you include enough carbonate in the solution (>0.5 molar), it prevents oxidation by aeration (though of course does nothing for auto-oxidation), while also as expected provides a ton of buffer capacity
The last claim is especially crazy to me, given that more carbonate seems to accelerate oxidation, but I've never attempted to use such a strong solution of carbonate (basically near solubility limit). Applications could include: A stable solution of ascorbic acid in alkali, applying the same concept to hydroquinone (with a peroxide scavenger such as oxalate), a stable (non-lith) print developer could be produced using ascorbic acid + something superadditive (phenidone with lots of anti-fog?), and likely other applications.
My real question is do these concepts actually hold weight? The patent is such a late (90s) patent that it gives an excellent reference of prior art in the field, but these claims seem rather extreme to me, and completely unexplored in the home formulation game. Any chemists care to weigh in?
edit: The only developer I can think of to potentially exploit this effect is the legendary Ansco 130. It uses more carbonate in it's stock solution than the 0.5 molar threshold. It's longevity has always been upheld to be because of the use of glycin, but maybe the amount of carbonate and the fact that it's used as a stock or 1:1 solution (whereas most solutions like this would be diluted much further) is a bigger key. Creating a stable developer with so much carbonate in the working solution would definitely be a challenge regardless
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