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Determine if nickel is present in silver beads?


#1

I imported 2200 grams of silver beads from India to use in some of my
necklace designs. I would like to determine more or less if the
silver content is .925, as promised. I don’t have a testing kit,
but my jewelry books say that is not reliable anyway. And not even
Rio sells the so-called ‘silver star’ to test the grade of silver …
I suppose because no one wants to go to the trouble to test silver
since it costs little anyway! The cupellation method requires too
many components to buy – it’s not worth it.

Why even bother trying to determine the silver content? Because I
don’t want to buy from a merchant unless I’m sure of what I am
getting, and I don’t want to represent in my own jewelry something
that isn’t true. So I am trying to crudely or roughly determine how
much silver is present.

I did a crude ‘meltdown’ test in a Neycraft kiln. The bead did not
melt even at 1700 degrees F registered by the oven pyrometer.
Therefore I suspect there is some nickel in these beads, but I was
unable to find any charts or graphs that would give me melting
temperatures of silver/nickel alloys. During the heating some fine
silver did come to the top of the bead.

Anyone have any suggestions or ideas of what the actual alloy might
be?

Carole


#2
    I imported 2200 grams of silver beads from India to use in some
of my necklace designs.  I would like to determine more or less if
the silver content is .925, 

I don’t think that there is a simple way of quantitatively
determining the silver content of an alloy. I have done it for
solders but I used wet chemistry methods, having trained in analytical
chemistry - a good many years ago and I still have the chemicals and
equipment to do it, which includes a sensitive balance weighing to
0.0001grams. I do have the time - but not the inclination these days.
For just qualitative analyses the alloy is dissolved in nitric acid,
and the presence of copper determined with ammonia which gives a blue
colour, or the presence of nickel using a solution of dimethylglyoxime
which gives a red colour. Modern analytical methods use very expensive
and highly sophisticated machines and instruments. Most big towns
have a laboratory which will undertake such analyses, but the cost is
pretty high. Like between US$50 - $60 per element. (if you’re lucky)
Cheers, – John Burgess; @John_Burgess2 of Mapua Nelson NZ


#3

Hello Carole,

     Anyone have any suggestions or ideas of what the actual alloy
might be? 

I can’t tell you what the alloy is, but I offer some comments. First,
how much are you willing to pay to know? Once you have figured that
out then you can define your choices: Atomic absorption
spectrophotometry, x-ray fluorescence analysis and so on.

Next, here’s a suggestion I learned from grade 12 chemistry. It’s the
borax bead test. See page d114 of the CRC handbook of chemistry and
physics. In oxidizing flame, silver is colourless, copper is green
(hot) and blue (cold), and nickel brown and red (cold). In a reducing
flame silver is grey and opaque, copper is red, and nickel is grey and
opaque. We know that sterling forms a fire scale when heated even
mildly. Any present?

Finally you could try applying Archimedes Principle.

David in Victoria, where summer has finally arrived (at least for the
next five days)