What is aqua regia?

Aqua regia is a mixture of concentrated nitric acid and hydrochloric acid, usually one part of the former to three parts of the latter by volume. Way back in the 8th century AD, an alchemist by the name of Muhammad ibn Zakariya al-Razi (854-925) prepared the first recorded batch of aqua regia, a mixture of nitric and hydrochloric acid in a 1:3 ratio. It was only in the 14th century that it made its way from the Middle East to Europe.

Aqua regia is highly corrosive in nature and capable of dissolving gold and other resistant substances like platinum. Named from the Latin for “Royal Water”, this volatile mixture turns from colourless to a fiery yellow-orange within a few seconds of being prepared. Adding to that dramatic effect, it also fumes vigorously. Because its components are so volatile, it is usually only mixed immediately prior to use. Pure gold of up to 99.999 purity can be obtained through sophisticated chemical methods using aqua regia.