Without any professional device, is there any way to have a test or wild guess on whether a piece of gold jewelry is made of pure gold (i.e. 24K) with little or no impurities? And how reliable will that be?

Edited August 9, 20223 yr by kenny1999
grammatical mistakes

various types of gold are alloyed to silver, copper, zinc, etc.
This affects the density.

I would think accurately weighing the sample, and determining its volume by water displacement, would yield a density which can be compared to pure gold.
It would be as reliable as your weighing/measuring equipment.

I read this: Get some white vinegar in a dropper and put some partially on the gold object in small container, such that not all of the object is wetted. Leave it 5-8 minutes and see if there is any difference in colouration between the exposed area and unexposed area. If you see no difference, it's pure. This a is yay or nay test and won't tell you the proportion.

Edited August 9, 20223 yr by StringJunky

There are kits you can buy on line to test the purity of gold using acid.  They are cheap and easy to use.

29 minutes ago, Bufofrog said:

There are kits you can buy on line to test the purity of gold using acid.  They are cheap and easy to use.

And within a few short weeks I’m sure at least one kind entrepreneurial soul will join our fine community here to share a link to great one!

6 hours ago, MigL said:

various types of gold are alloyed to silver, copper, zinc, etc.
This affects the density.

I would think accurately weighing the sample, and determining its volume by water displacement, would yield a density which can be compared to pure gold.
It would be as reliable as your weighing/measuring equipment.

I seriously doubt that determining volume by water displacement can be anything like accurate enough, unless the object is huge. You would be talking μl. 

From what I have read, a more realistic way would be by difference: getting a sample of known gold of the same weight, putting the two either side of a balance and then submerging both in water, to see whether the scale tips or not, as any difference in volume will create a difference in buoyancy.

 

Gold is nonmagnetic, so being attracted to a strong magnet would indicate impurities.

1 hour ago, swansont said:

Gold is nonmagnetic, so being attracted to a strong magnet would indicate impurities.

1. Are all possible (or common) impurities mixed with gold jewelry magnetic?

2. If the impurities are wrapped by the pure gold, would it still be attracted to the magnet?

3. If the content of impurities isn't really high, (but the jewelry is not as pure as 24K gold) will it still attract to the magnet?

11 hours ago, kenny1999 said:

a piece of gold jewelry is made of pure gold (i.e. 24K)

Gold jewelry is almost never made of 24 karat gold because it is too soft for things that have been worn....

https://www.google.com/search?q=24+karat+gold+as+it+is+too+soft

There are 24k coatings.. with internal stuff made from something cheap..

 

Edited August 9, 20223 yr by Sensei

20 minutes ago, kenny1999 said:

1. Are all possible (or common) impurities mixed with gold jewelry magnetic?

2. If the impurities are wrapped by the pure gold, would it still be attracted to the magnet?

3. If the content of impurities isn't really high, (but the jewelry is not as pure as 24K gold) will it still attract to the magnet?

Only some possible impurities would be attracted to a magnet. Pure iron and nickel (alloys might not be magnetic), along with other less common materials.

Gold-plating wouldn't hide this, but it probably would not detect small amounts of impurities

6 hours ago, exchemist said:

I seriously doubt that determining volume by water displacement can be anything like accurate enough,

And I said

13 hours ago, MigL said:

It would be as reliable as your weighing/measuring equipment.

For gross contaminants, like 10 k or 14 k gold, lab grade equipment should work.
But you may be right about higher purity grades.