[Jewelry making - Article 00047] - [Orchid] Verifying Gold Alloys

[Dietrich Riemer]

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    I have to verify the gold content of medals and orders to determine
    whether they are real or fake. I want to determine the karat value of
    the gold alloy. 

    I use a precision scale, hang the part on the scale, zero the scale
    and then immerse the part in water. The weight reduction tells me the
    volume of the part. I then weigh the part itself in air. Dividing the
    weight by the volume gives me the density. A comparison with known
    densities of metals and alloys tells me the composition: 8.9 is brass
    or copper, 10.4 is silver, 11.5 to 19.3 is gold between 10 and 24
    karat. 

    Is this approach commonly used or are there other non-damaging
    methods? In my opinion, the test must not just check the surface
    (like the stone-rub and acid test, which in addition damages the
    part) because plating can falsify the results. 

    A discussion of gold-alloy testing or a reference to any earlier
    exchange in this Forum would be appreciated. 

Thanks,
Dietrich

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