Gold and Platinum belong to class of noble metals in the sense that gold and platinum do not react with almost any chemical reagent.
Aqua Regia is the chemical mixture which consists of 3 parts of concentrated hydrochloric acid and 1 part of concentrated nitric acid and this mixture can dissolve gold and platinum.
The reaction is as follows:
Au + HNO3 + 4 HCl → HAuCl4 + NO + 2 H2O
