what are all possible ways of testing 999.9 or 24k gold?

[kenny1999]

Without professional devices, what are all possible ways of testing if gold jewellery is pure and real gold, i.e. 999.9 or 24k? It doesn't matter if it's not 100% accurate but is there any way to make a good estimation?

[exchemist]

1 hour ago, kenny1999 said:

Without professional devices, what are all possible ways of testing if gold jewellery is pure and real gold, i.e. 999.9 or 24k? It doesn't matter if it's not 100% accurate but is there any way to make a good estimation?

You could try Archimedes' method, viz. establish the volume of the object via displacement and then weigh it, thus determining its specific gravity. This would only work for objects with a fairly large proportion of metals other than gold in them, but then that is the case for a number of the alloys used in jewellery: https://www.thoughtco.com/composition-of-gold-alloys-608016   

[MigL]

Pure gold is resistant to all acids, except a mixture of Hydrochloric and Nitric, called Aqua Regia.
I would think any mixture, or alloy, of gold would have its 'impurities' affected by other acids, so that might be a simple test ?

sand off a few grains, and drop some readily available Hydrochloric or Sulfuric acid on them; see if you get any bubbling action.

 

[John Cuthber]

8 hours ago, MigL said:

Pure gold is resistant to all acids, except a mixture of Hydrochloric and Nitric, called Aqua Regia.
I would think any mixture, or alloy, of gold would have its 'impurities' affected by other acids, so that might be a simple test ?

sand off a few grains, and drop some readily available Hydrochloric or Sulfuric acid on them; see if you get any bubbling action.

 

Doesn't really work.
Only the impurity atoms on the outside are exposed to the acid; the rest are effectively protected by being "gold plated".

Density is a better option.
Even this is pretty good.
https://en.wikipedia.org/wiki/Touchstone_(assaying_tool)

On a completely pointless pedantic note, there's (at least) one acid which will attack gold.
 

 

[MigL]

On 4/6/2024 at 8:35 AM, John Cuthber said:

one acid which will attack gold

Did not know that about Selenic acid.
Thanks John.