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Posted by Bernhard Kuemel on April 17, 2008, 7:35 am
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Hi rcm!
I've been curious about gold leaf a long time and eventually I
bought this affordable offer on ebay:
200 pcs of 24K Gold leaf - gold sheets !!
http://cgi.ebay.at/ws/eBayISAPI.dll?ViewItem&item=360036418931
I got suspicious at first when I weighed some leafes. I got about 1g
for 14.90$ while gold was at 29 $/g. The dealer did not answer how
this was possible.
It turned out what I got is coated plastic foil. The "gold"
dissolves in hot concentrated nitric and hydrochloric acid (not
mixed, aqua regia) and leaves the plastic foil behind. The leaves
burn quickly when touched by a flame and no gold remains visible in
the ashes.
They claim:
Size : about 1.78" x 1.78" or 4.5 cm x 4.5 cm
Thickness : around 0.2-0.4 microns
That would be 4.5e-2^2 * (0.2-0.4)e-6 * 100^3 * 19.3 * 200 = 1.6-3.1
g Gold. Had I calculated that before I would not be surprised with
what I got. But as it is I feel defrauded. They even show pictures
of someone hammering gold leaf and showing the leaf in the pile.
This suggests they are offering traditional gold leaf.
I tried to make a gold mirror by attaching the gold to a small thin
glass sheet, but it would not become flat. I wanted to use the
mirror to reflect a laser beam. Also I thought of making a gold leaf
electroscope. It may be difficult to contact the gold layer through
the plastic. It is totally unsuitable as electrode to electrolyse water.
Is this a fraud? Is 14.90$ a fair price for what I got? Is the
coating 24K gold? Would a 24K gold coating dissolve in HCl or HNO3?
What does 'RG' mean in '200 pcs of 24K Gold Leaf (RG)'? Is 'gold
leaf' a correct term for gold coated plastic foil? How thick is such
a gold coating on plastic foil compared to traditional gold leaf?
Thanks, Bernhard
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