is anyone aware of research conducted about the super aditivity between phenidone and citric acid. the knowledge would be importznt if one wants to substitute m an q developwrs with p and c. thanks in advance.
I believe you mean ascorbic acid since citric acid is not a developing agent.
Phenidone and ascorbate ion do form a super additive mixture. However what is envolved is not a simple substitution of ascorbic acid for hydroquinone. As has been mentioned several times on APUG the resemblence between these two developing agents is superficial and several adjustments must be made to a hydroquinone developer to convert it into an ascorbate developer. To mention a very important difference between the two developing agents, hydroquinone is a is an uncharged molecule while ascorbic acid in solution is a negatively charged ion. This has a important effect on the adsorption of the developing species on the silver halide grains. To explain what occurs is very complex and anyone interested should read up on the development process in particular the Charge Barrier Effect.
It's not known what is in the archives of Kodak, Ilford and Foma, who sell derivatives of PC, or where Kodak's archives are.There are references to work by Gainer and Ryuji Suzuki in this thead:
(there was a url link here which no longer exists)
Here's one from Patrick Gainer: http://unblinkingeye.com/Articles/Synergism/synergism.html
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