I fell victim to this one myself. I bought a few "mini gold coins"... They are sold as if they were solid gold, or gold filled. They MIGHT be gold plated, but my chemistry experiments on them indicate they are most likely brass.
The coins are usually tiny, say, an eigth of an inch in diameter, maybe bigger. They sell for a few dollars...
Well guess what? THEY ARE NOT GOLD. Not saying gold mini's don't exist... The 1/10th ounce gold eagle for instance is quite small, but it is still larger than a mini, and you can tell for sure that it is real gold just by holding it.
The mini's I bought, dissolved in their entirety in nitric acid. Gold is a noble metal. Very few mixtures will dissolve it. Only the most powerful of acids, such as Aqua Regia will dissolve Gold. And that is such a potent combination I dare not even mess with it. Nitric on the other hand, is incapable of dissolving Gold. I use it in removing silver and copper from gold that I find or melt. It works beautifully. Well... I thought ok... I have these mini gold coins, and I know they can't possibly be Gold, so I put them in the Nitric.
The result was, they dissolved completely, leaving a green/blue solution. Greens and Blues are what you get when you have copper, and the color can change depending on the other metals in the alloy. And it dissolved within seconds. I've never seen anything react so fast. Gold does not react with Nitric, Sulfuric, or Hydrochloric acid. However, Gold can form Chlorides via RedOx reactions, but it is a VERY slow process... And Nitric Acid would have formed Nitrates, not Chlorides.
There should have been anything at the bottom of the beaker if there were any Gold. There was not one iota of Gold in the Beaker when I filtered the solution. The filter was completely clean, meaning EVERYTHING dissolved.
Conclusion: STAY AWAY FROM MINIATURE GOLD COINS OR AT LEAST BE AWARE THEY VERY RARELY CONTAIN ANY GOLD IF AT ALL!
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