Potassium Bromide gone solid need opinion please

Discussion in 'B&W: Film, Paper, Chemistry' started by AndreasT, Feb 10, 2013.

  1. AndreasT

    AndreasT Member

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    I have some Potassium Bromide from a friend and it has backed together. Now I would like to use it for developers. As far as I know it last indefinitely. What I am concerned about is how to measure it for recipes. Should I leave the bottle open and measure it as monohydrate after awhile. Or put it in my oven and dry it out and use it as anhydrous.
    Or discard of it.
    In recipes they always talk about anhydrous and monohydrate sodium carbonate but not with other chemicals much.
     
  2. Athiril

    Athiril Subscriber

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    It has a high melting point (relatively speaking to your oven), so I would dry it out.
     
  3. Bill Burk

    Bill Burk Subscriber

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    I keep hearing advice to make a 10% solution and measure from that. Seems you could do that by weight.
     
  4. Paul Verizzo

    Paul Verizzo Member

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    I've a bottle of PB since forever, at least 20 years.

    I suggest that you just put it in an oven or toaster oven at the very lowest heat and let it dehydrate. The physical nature may not change much, you may need to smash the heck out of it, or do mortar and pestle, but the chemical will not change.

    Since PB is just a restrainer, it's not like you can really mess things up.
     
  5. Gerald C Koch

    Gerald C Koch Member

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    Potassium bromide does not form any hydrates. My suggestion would be to chip some out for weighing to make a 10& solution. If necessary some larger pieces could be ground up in a mortar.
     
  6. jochen

    jochen Member

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    Hello,
    put it into a clean plastic bag, lay it on the floor and pulverize it with a hammer. Or use a porcelain mortar from laboratory equipment.
     
  7. Mike Wilde

    Mike Wilde Member

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    I have a small mortar and pestle that normally lives on top of my jar of KBr, dedicated to breaking it up. About $6 from a specialty cooking store.

    I expect to find it gone to a rock like state.
     
  8. AndreasT

    AndreasT Member

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    Thanks for the answers. It helps.
     
  9. Photo Engineer

    Photo Engineer Subscriber

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    I bought a huge bottle of Potassium Bromide in the '50s. It is still good.

    The nature of the halide salts is to clump! They all do. Table salt clumps. They put an additive in it to prevent clumping and that is why table salt should not be used when you need Sodium Chloride in a photographic formula.

    PE
     
  10. cliveh

    cliveh Subscriber

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    Sorry to go off thread a little here, but how does the non-clumping additive effect Sodium Chloride in a photographic formula? The reason I ask, is that I have never noticed a problem with this.
     
  11. Photo Engineer

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    There are several anti-clumping ingredients. I know that Sodium Silicate is used and (IIRC) Sodium Thiosulfate is used. Either has an effect on imaging. The Silicate can "dilute" the halide effect, and it can also fail to dissolve completely thus leaving a residue in the film. The effect of the hypo is obvious even at low levels.

    But, I am speaking more about emulsion making than processing. The effects are far more pronounced in emulsion making than in solution makeup. Still, there are effects in either.

    PE
     
  12. AndreasT

    AndreasT Member

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    For what does one use sodium chloride in a developer?
    By the way how long does benzotriazol last?
     
  13. Paul Verizzo

    Paul Verizzo Member

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    A. Iodized table salt is a ready source for potassium iodide, a very powerful restrainer. Whether the additives that PE expresses concern about would affect a developer and film one would have to experiment. It has been used for years for this purpose and some recent intertube explorations yielded no problems announced.

    B. "Forever." Like my potassium bromide, something like 25 years and doing just fine.
     
  14. AndreasT

    AndreasT Member

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    How powerful does powerful mean? How does one know how much to use?
    By experimenting?
     
  15. AgX

    AgX Member

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    In Germany (as alternative to Calcium or Magnesium Carbonate) Sodium, Potassium or Calcium Ferrocyanide is used in table salt.
     
  16. cliveh

    cliveh Subscriber

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    But from what I understand, at concentrations of less than 2%.
     
  17. AndreasT

    AndreasT Member

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    Isn`t all this posionous?
     
  18. Paul Verizzo

    Paul Verizzo Member

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    "Powerful" means, relatively, restraining action to the weight.

    A quick glance at some C-41 formulas shows, typically, about 1.5 grams of potassium bromide and 1.5 MILLIgrams of KI.

    The only practical way to measure that, even with something like my Ohaus Centrigram scale, is weigh out and put in water or alcohol, then use small measures from there.

    Glancing at the iodized salt labels, I see that some actually tell how many milligrams (or was it nanograms?) were in a serving. Good ole grocery store photochemicals. Salt, sodium carbonate posing as washing soda, borax, and in a less paranoid age, sodium hydroxide as drain cleaner.
     
    Last edited by a moderator: Feb 11, 2013
  19. AgX

    AgX Member

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    Less than 0,002%.
     
  20. Photo Engineer

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    Paul, I think you meant MILLIgrams of KI.

    And, the hypo is present in table salt to preserve the KI which decomposes into Iodate and Iodine.

    Why use table salt in a developer? For the KI present. To restrain slow Azo type emulsions, and also it is used in Microdol-X as a silver halide solvent, and is used in some fix formulas and wash aids!!!

    The Silicate is water soluble but can be retained as it is a large molecule and washes out slowly and the Iodide and hypo are not very good. Ferrocyanides can cause fog. So, it remains to be seen whether these can be used without harming your precious negatives. I don't use table salt for any purpose. I did the experiment one time and the result in making an emulsion was a disaster, as Silver Silicate formed as did Silver Iodide. The tiny amount of hypo also increased fog!

    PE
     
  21. Gerald C Koch

    Gerald C Koch Member

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    The effectiveness of the halide ions Cl-, Br-, and I- as restrainers is roughly proportional to the ratios of the solubility products of the corresponding silver halide; AgCl = 1.8 x 10-10, AgBr = 5.3 x 10-13, AgI = 8.3 x 10-17, . Thus KI is 1000X more effeftive than KBr which in turn is 1000X more effective than NaCl.
     
    Last edited by a moderator: Feb 12, 2013
  22. Photo Engineer

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    Thanks Jerry. Good explanation. I should have done that in the first place.

    PE