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  1. #1

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    Pinacyanol Salts

    Hi to All,
    In going through the old literature on spectral senitization one of the more avalible dyes is Pinacyanol. I looked these up in the Sigma-Aldrich catalogue and found that I can probably purchase the chloride or bromide salts, but not the Iodide salt. I base this on the fact that the Toxicity rating for the I salt is "T". The rating for the Br and Cl salts is "X". Past experience tells me that I can buy X, but not T.
    Many of the old dye names are no longer used. So I cannot find what the old practioners were writing about.
    I have the two dyes that PE recomended for spectral sensitization. But , after "convenience" fees shipping and taxes, these cost close to $200/g.
    I want my work to be accesable to anyone who is intrested. These dyes might be cost prohibitive to many.
    My question is, dose anyone know the absortion peeks for the Br and Cl salts of pinacyanol?
    Thanks
    Bill

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    Bill;

    Most companies that sell such salts will supply a spectrum of the compound. This curve will closely mimic what happens in an emulsion if you slide the peak towards longer wavelengths.

    I have no knowledge of this dye at the present time, and the dyes that I recommended to you will probably last a long time in spite of their costs. I use about 50 - 100 mg of dye / mole of silver which is about 108 grams. Therefore, I can work up over 1 kg of silver in an emulsion with that 1 gram ($200) batch of dye. At current prices, the silver is far more expensive than the dye.

    And, Erythrosine and some other dyes similar to it are in the $20 / gram range.

    PE

  3. #3

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    Bill - Gorokhovskii in "Spectral Studies of the Photographic Process" (1965) calls pinacyanol "the classical carbocyanine sensitizer [...] for the yellow-red region of the spectrum". It is shown as having two absorption maxima, one at about 580 nm and another at 630 nm. The maxima at 580 is dominant in alcoholic solutions, and becomes weaker as gelatin content increases. The maxima at 630 absorbs less than that of 58o in alcoholic solution, but absorbs more than 580 as the gelatin concentration increases.

    So it looks to me that for your use, 630 is the maxima to consider.

    Ron - I think Bill is also asking about the effect that the salt form will have. That is, does the chloride salt of pinacyanol have a differing effect than the bromide salt? I'm guessing the halide will just go into solution and not have an appreciable effect on the emulsion. And the amount from the dye will be pretty small as not much dye will be used in a particular emulsion batch. So it probably doesn't matter if he uses the chloride or the bromide, right?
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

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    Kirk, Bill;

    The salt type will affect the emulsion. For example, an Iodide salt on a Bromide emulsion will cause Iodide to adsorb to the crystal as well and eject bromide. In fact, Iodide may compete for the crystal surface in preference to the dye. Or the Iodide may promote "J" aggregation shifting the sensitivity as much as 100 nm. I cannot predict results without the experiment.

    I can say that the longer wavelength will "probably" predominate or even shift further when adsorbing and the salt type will have some effect.

    PE

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    Quote Originally Posted by Photo Engineer View Post
    For example, an Iodide salt on a Bromide emulsion will cause Iodide to adsorb to the crystal as well and eject bromide. In fact, Iodide may compete for the crystal surface in preference to the dye. Or the Iodide may promote "J" aggregation shifting the sensitivity as much as 100 nm. I cannot predict results without the experiment.
    So then if a chloride salt is available (as it is in this case), that would be the safest choice, as chloride will not displace any bromide or iodide on the silver halide crystal if bromide or iodide is present on the crystal.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  6. #6
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    Kirk;

    That is probably true, but then you have to be careful if you are working with a paper Cl or Cl/Br emulsion and want to sensitize it. You can probably adjust for the counter ion, but that takes experimentation and dye.

    PE

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    Hi PE and Kirk,
    Very interesting. I may have some difficulty purchacing anything from Sigma,though. They have gotten tighter since I last did it.. Well, here goes not'in!
    Bill

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    Good luck, Bill!
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

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    Is the synthesis of Pinacyanol Salts very complex?

    Emulsion.

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    Not if you have a fully equipped lab and all of the starting materials. Also, not if you know what you are doing.

    The usual lab tech that does this, does it under the supervision of an MS or PHd organic chemist. The lab tech has either an AAS or BS in chemistry. This is for rote work. For original work with new dyes, the PHd chemist usually does his own lab work so that he can work out the kinks.

    PE

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