Acid testing of leaf gold

[Christer]

Hello Guys,

I bought some leaf gold, I heard it was 23.5 K, but I suspect it was not the case. Therefore I submitted it to some acid tests, 21K, 18K, 14K and 8K (bought from a reliable source).

The acid testing is however designed to be applied to a streak on the touch stone but naturally this is difficult to achieve with leaf gold since it is so very thing, so I just applied some acid on it directly instead.

Now to my question and the reason I seek your help / input:

Is this method of acid testing 100% appliable to lead gold? Or could it be hypothetically that the gold for example dissolved in a 14K acid test even the gold is of a higher grade? I suppose not and that I was fooled by the person who sold it.

My ”gold” was desintegrated by all these acid tests except for the 8K acid. It did not even resist 14K acid. So I guess the grade is somewhere between 14-8 K. By the way, I noticed a blue coloration so copper is obviously present (chloride).

All input are wellcome and thank’s in advance!

Cheers,
Christer

 

[FrugalRefiner]

I suspect what you have is imitation gold leaf. It's mainly copper and zinc.

Dave

 

[Christer]

Hi Dave,

Any simple test that I could do to verify your hypothesis?

Br,
Christer

 

[butcher]

Put a tiny piece of foil in test tube cover with water and a drop of nitric acid.
Do this outdoors, so you do not breath the deadly gas.
if gold it will not be attacked, if not it will dissolve.

 

[FrugalRefiner]

What butcher said, but it sounds like you've already done that with your test acids. You mentioned the blue color indicative of copper. I wouldn't expect that from real gold leaf.

Dave

 

[Christer]

Thank’s for input.

@butcher: yes nitric acid is a possibility. And see if any gold precipitates (dark particles).

@Dave: copper gives raise to blue coloration in acids so I don’t find this strange at all, considering that copper is the metal that is usually alloyed with gold.

 

[lazersteve]

You could rule out it being pure Au with the nitric test mentioned above (pure Au has no Cu, therefore no blue plus pure Au is unaffected by nitric ).

Another purely mathematical approach is to simply accurately measure the length, width, and thickness in cm. Next multiply these three numbers together for the volume in cc (cubic centimeters). Now weigh the foil as accurately as possible in grams.

Finally divide the grams by the cc figure to get the density.

Any figure below 10 g/cc and you likely have no gold present. Pure gold leaf should be over 19 g/cc if your measurement numbers are accurate.

18kt approximately 15.5 g/cc
14kt approximately 13 g/cc

Xrf is another quick option if you know a place that will shoot it for you.

I hope this helps,

Steve