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  1. #1

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    Dimezone-S: the other tanning agent

    I think I might have mentioned this once before in passing, but figured I'd mention it again. While not staining developing agents, certain Phenidone derivatives with 4-position hydroxymethyl substitutions can tan/harden gelatin imagewise, forming the same type of relief image normally associated with hydroxybenzene agents such as pyrogallol, HQ, catechol etc. Dimezone-S is one of these compounds.

    The tanning mechanism is different, but the end result is the same. In the case of these particular 3-pyrazolidones, there is an aldehyde oxidation product which hardens the gelatin imagewise. Apparently the aldehyde does not react with ascorbate, nor does it react much with sulfite (although this appears to depend to some degree on pH), meaning tanning action is much less sensitive to the presence of sulfite than in the case of hydroxybenzenes.

    Just some food for thought.

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    So have you made any home brew with dim-s to compare to other pyro developers? I am assuming, that since you mentioned sodium sulfite, you are looking for "some dissolving action? or just enough sodium sulfite as a preservative? I am also assuming you can use either potassium carbonate or sodium carbonate to adjust PH? And Typical restrainer Of KBR? I have only seen ( as much as I can remember) the Suzuki paper developer formulae with dim-s. Oh!! do you use dim-s with metol for super action? or just some ascorbic acid?? whats the . . . . ah, you know. . . ah "trend"?

  3. #3
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    An aldehyde can react with gelatin, but can it crosslink?

    The answer is that some can't and some can. You must have formalin, glyoxal, succinaldehyde or glutaraldehyde to crosslink and harden, but the ones in between just react but do not harden because they cannot crosslink.

    PE

  4. #4
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    I am not a chemist, so please bear with me: if that Hydroxymethyl-substitution is important, one could argue that it somehow interacts with the gelatin. And there is an =O end right next to it on the ring, so you'd have two groups that interact with gelatin, satisfying your requirement for hardening/tanning action.
    Trying to be the best of whatever I am, even if what I am is no good.

  5. #5

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    In Xtol, say, suppose the Dimezone-S oxidation product is regenerated by ascorbate to give a normal contrast negative, does the OP claim that at the same time there is an aldehyde oxidation product formed which is not regenerated by ascorbate?

  6. #6
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    None of the Phenidone family of developing agents is regenerated in any way. If the ring opens, that is it for the molecule.

    The ring opening produces the original two pieces of the condensation which are not developing agents.

    One may react with gelatin, but you need it to react at 2 positions for any hardening effect.

    The aldehydes are noted by the mnemonic "OMSGAPMMM". This list omits the leading "F" though because it has only one aldehyde group. The aldehydes in that list all act as hardeners. Oxalic (glyoxal), Malonic, Succinic, Glutaric and etc. Formalin is unique.

    PE

  7. #7

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    I originally found this reference in Haist. The reference is to this interesting Kodak patent:

    http://www.google.ca/patents/US3453109

    Alan, the patent claims the aldehyde released "...does not react to any appreciable degree with ascorbic acid, and only to a limited extent with sodium sulfite, especially at high pH value."

    Rudi, I wonder if my low contrast Dimezone-S/ascorbic acid experimental formulas, which are relatively low in sulfite anyway, are tanning the film imagewise.

    It is not made clear in the patent whether or not pH has a direct effect on the tanning action of these 4-substituted 3-pyrazolidones. The test developers in the patent are high pH formulas (pH 11.5) but this is not explicitly addressed as a variable (other than the comment about the degree of aldehyde-sulfite interaction decreasing as pH is increased).

  8. #8
    Photo Engineer's Avatar
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    If this indeed works, I have to take back all of what I said.

    However, it looks clean in the patents but was never used for some reason and yet it would have made a better and more stable developer than the current Matrix developer. So, I wonder what is up with this?

    Bill Lee, the inventor moved up into Dick Henn's position shortly after this patent published. He could have pushed it from that position.

    PE

  9. #9

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    Quote Originally Posted by Photo Engineer View Post
    None of the Phenidone family of developing agents is regenerated in any way. If the ring opens, that is it for the molecule.

    The ring opening produces the original two pieces of the condensation which are not developing agents.

    One may react with gelatin, but you need it to react at 2 positions for any hardening effect.

    The aldehydes are noted by the mnemonic "OMSGAPMMM". This list omits the leading "F" though because it has only one aldehyde group. The aldehydes in that list all act as hardeners. Oxalic (glyoxal), Malonic, Succinic, Glutaric and etc. Formalin is unique.

    PE
    Mason, Photographic Processing Chemistry p80 reports work that suggests that development by phenidone is effected by a phenidone anion giving an uncharged free radical. He refers to the reduction of the intermediate oxidation product by hydroquinone. Perhaps something similar happens with Dimezone-S and ascorbate, though I am not sure if that would be called regeneration.
    It is a different reaction from that said to produce aldehyde oxidation product.

  10. #10

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    Interesting background, Ron. Thanks. I didn't know Lee held that position in the company.

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