18k gold tests as 22k gold with acid test

[Goldbar666]

Hi everyone. A friend of mine owns a pawn shop. A guy brought 3 flat pieces of gold unmarked to the pawn shop the past week. My friend cut the pieces into small pieces and scratched them and acid tested them. All 3 pieces weighed in at close to 83grams each. They passed the 22k test flawlessly. The gold was easy to bend. It seemed a bit fishy after a few days as he never bought 22k gold and took the to a friend who has some kind of machine that tests metals for purity correctly. Btw. My friend has been buying gold for 20 years and has rarely been wrong. The machine test indicated 18.6k gold and some other metals. Is it possible to mess with gold so that it passes as 22k?

Thabks for your help

 

[Geo]

Gold test solution is just aqua regia in varying concentrations. Nitric acid decomposes over time when exposed to light and the atmosphere. The test solution could simply be past it's useful age. Try testing the test solution against a piece of known content gold to ensure the test solution is still good.

 

[Geo]

Also, I received good advice from Harold to get a acid test kit with gold test needles. The needles are tipped with known karat gold. Make a streak the the test needle and a streak with the piece being tested. Put the test solution one one spot of each streak and observe any changes from one to the other that does not match.

 

[Goldbar666]

Thanks for your answer. The test has been repeated several times with different kits. All new. The composition of the gold simply fooled the test. Only the spectro analysis gave a precise reading of 18.6k. All other tests indicated 22k

I wonder if it is possible to fool the acid test with some kind of gold mix. Hmmm

 

[Shark]

Are you sure the machine reads it right? I had some silver bars that I had tested that read at less than 94%. All were name brand bars labeled as 999 fine.

 

[nickvc]

I’m with shark, I suggest finding someone with an xrf gun and try it again, many buyers have them especially if they are buying in quantity.

 

[rickbb]

As Geo said, if you are not testing against a known standard, such as the needles made for such use. You really have no idea what the karat is.

The correct way to use the acid test is to make a streak with each of the standard testing needles and beside each streak make a streak with the piece you are testing. That way you are comparing apples to apples.

 

[nickvc]

Another possibility is to take say a sovereign which is 22k and ask the original tester to try it, or an American coin which are 90%, if it reports a lower figure then your original test was wrong.

 

[Goldbar666]

Thanks guys for the help and ideas. I will give it a try. Just went through a long lecture on mixing different alloys like platinum etc. when melting down gold to trick but no precise details on what those percentages are. Sound to me like someone is making good money on his chemistry knowledge by selling 18k gold to unprofessional or let's say not so trained pawn shop owners as 22k gold )