The refined gold as all precious metals is carried out using « aqua regia », an acid which is a mixture of nitric and hydrochloric acid.
However, there is another method that is unknown.
This method is called by quartation is first literally put a quarter of a gold content of an alloy.
For this, we will add to a gold alloy the amount of copper required for the gold is + – 25% of the total mass.
This technique can be very useful to make a very precise analysis artisanal gold nuggets Africa or powder.
With a blowtorch to melt a small amount of + – 10 gr gold + – + 22 carat or – 9 grams of estimated gold. Weigh this amount accurately with a scale 0.01 gr.
We will add + – 30 g of copper (or quartation inquartation) and make a new alloy that is gently poured Drop Count over a body of water to the blasting and give a lot in this area gold depleted.
(We also do the little quartation with fine silver, it can be recovered by precipitating with salt in the spent acid)
Then, with nitric acid in a stainless steel pan or heated Pyrex, you attack the gold granules.
It is highly recommended to do this in a garden, this providing a suitable mask and gloves.
Nitric acid will react strongly and dissolve the copper and silver contained in the alloy.
We replace or fresh nitric acid refills as you notice the reactions of it.
Once the path is that there is no reaction, the process is stopped and rinsed
The fine gold remains with water preferably distilled.
Once dry, the gold is weighed and end remaining with the initial weight of 22 carat with a rule of three we can calculate its purity.
For example an initial weight of 9.93 grams of 22 carat gold gives a weight of 9.03 gr gives end
The following calculation 0.903 / 0.993 = 0.9093 or 90.93% x 99% = 90.02% * of gold content in gold late departure.
* It is best to put this 99% purity for some metals like iron may not have been dissolved by nitric acid.