[Jewelry making - Article 00256] - Re: [Orchid] Playing with palladium

[Alden & Glenda Blood]

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    Douglas: You would not need much chemistry to evaluate the pickle
    potential of the ionic solvent used in the British patent to recover
    Pd values from spent catalyst.  The Edison approach should be
    sufficient.  Some chemical concepts would be helpful in designing
    trials.  For example, boosting the chloride anion concentration to
    promote metal chloride complex formation (people use this kind of
    complex every time they add salt to vinegar when cleaning copper
    pots!) and using acids like citric acid or EDTA
    (ethylenediaminetetraacetic acid) in place of oxalic acid to promote
    clathrate complex formation, etc. These types of reaction rate
    increasing complexes are understood and used by non-chemists on a
    regular basis. 

    I don't believe the oxalic acid-choline chloride system would attack
    Pd metal. Dissolving an ionic substance with a strongly polar ionic
    solvent is one thing.  Oxidizing the metal with the ionic solvent is
    a horse of another color. I don't see what could/would be reduced in
    the system.  One would have to add an oxidizing agent. 

    I intend to check the British ionic solvent out as a potential
    pickle.  If it shows promise then some obvious substitutions would
    be in order for evaluation.  I am too long in the tooth to consider
    diving into the thicket of patent, manufacturing and marketing
    considerations if an effective general metal pickle does emerge. 

Captain Blood
"Marlinespike Seamanship in Precious Metals"
mariner AT tgtel.com

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