About Gold Aqua Regia

Aqua regia or aqua regis (Latin for royal water or king's water) is a highly corrosive, fuming yellow or red solution, also called nitro-hydrochloric acid.

The mixture is formed by freshly mixing concentrated nitric acid and concentrated hydrochloric acid, usually in a volumetric ratio of 1:3 respectively. It was so named because it can dissolve the so-called "royal metals," or noble metals, gold and platinum.

However, tantalum, iridium, osmium, titanium and a few other metals are capable of withstanding chemical attack from it

I am fully aware of this process as I used to work for a company who does carry out the mixing.