[Jewelry making - Article 01247] - Re: [Orchid] What is salt?

[Franklin Cox]

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    The Shor salt water refining system is just a simple salt cell. It
    has a vessel with a salt solution in it surrounded by more salt
    solution. As electric DC current is applied to the anode and the
    cathode, chloride ions travel through the vessel walls from the
    surrounding solution into it.. This creates an excess amount of
    chloride ions within it. These ions react with the gold alloy bar
    suspended in the vessel and cause the metal to go into solution as
    the current passes through it. This creates gold chloride, copper
    chloride, nickel chloride, zinc chloride, in a solution (water). The
    silver chloride is not very water soluble and  will fall to the
    bottom of the vessel as a white material. 

    Out side of the vessel is a solution that is now short of chloride
    ions. (hydroxide) Yes this is a very simplified explanation, but for
    an answer to the question asked it will do. The short answer is any
    solution with chloride ions in it will do. Table salt is sodium
    chloride. Sodium chloride will work in this system. Calcium
    chloride, ammonium chloride, sodium hypochlorite, and calcium
    hypochlorite are others that will work. I think that Shor uses
    ammonium chloride, but I am not sure. 

    The "Odour free Precipitant" is a selective precipitant. This
    material will cause the gold in solution to come out of the solution
    but leave the other metals in solution to stay dissolved in the
    water. The precipitated gold can easily be 995 pure. (but not
    necessarily) Possible selective precipitants are, ferrous sulphate
    (copperas), sulphur dioxide gas, oxalic acid and sodium nitrite. I
    read recently that sodium metabisulfite can also be used. My guess
    is that Shor uses sodium nitrite. I must tell you that this refining
    system works. I have made several of them over the years. I must
    also tell you it is full of hazards and potential pitfalls. Probably
    the greatest is the possibility of creating chlorine gas. The
    precipitated gold must be carefully cleaned and "fire refining"
    would also be advised. 

    I admit to not knowing what the catalyst is. I do know that it is
    not needed for the process to happen. A catalyst just starts and
    aids a reaction. I would be interested to know what they use. Having
    said all of this I can hardly wait to read what others have to
    offer. I love to read the responses here and love the ones from the
    chemically wise participants. 

    Possible other related questions are 

    1) testing the solution to know that all of the gold has been
    precipitated 

    2) dealing with the platinum group metals 

    3) dealing with silver in the alloy 

    4) dealing with lead and tin in the alloy 

    5) melting the precipitated gold into a button and removing other
    impurities as it is melted (fire refining) 

    6) disposing of the solutions that are made in an environmentally
    safe fashion. 

    7) the power supply (DC but should it be pulsating) 

    8) why not just use a trusted refiner? 

Oh what great fun this topic could be.
Franklin

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