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  1. #11
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    I almost forgot this.

    Here are the values you need. At 40C a 0.001 molar NaBr solution (0.1029 g/l) will give a vAg of about 67.5 mv. The pKsp is about 11.61, the pAg is about 8.595, and the pX (or pBr) is about 3.0152. Using KBr will offset this a bit due to the Activity Coefficient change and the Ionic Strength change. The answer will be very close though.

    The Activity Coefficient of the NaBr solution is about 0.96 and the Junction Potential is about 0.04. This all assumes a water solution with no silver present. If you want that it will cost extra and take a lot longer.

    This is what those three guys said. And, this is where you should be roughly at the end of a wash, at about 0.001 molar +/- a tad to be between 50 and 100 mv for optimum finish and keeping.

    Does this help? Please say yes! I hate lots of math.

    PE

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    Thanks - that gives me something to shoot for.
    Kirk

  3. #13

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    So that looks like around the 100-150 uS/cm level I mentioned above - that will be easy to measure with the meter I bought.

    Would there be any benefit from adding some KBr to the emulsion after the wash or we have enough there already provided we did not overwash?

    (And it did it - I made an emulsion at home. I've got it in the fridge digesting right now. I'll pull it tomorrow and wash it.)

  4. #14
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    Ahhh, the film emulsion? No, if you wash to rid it of the ammonia smell, that is about the right vAg value. At least it finishes well and keeps well for about a week or so. If you add KBr, do it after the finish. And remember that metal electrodes other than silver, and other salts released by porous electrodes affect the vAg and can change the emulsion.

    PE

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