Which liquid can dissolve gold

Gold is a noble metal, which means it is resistant to corrosion and does not easily react with most chemicals. However, there are a few liquids that can dissolve gold under certain conditions. One of the most well-known liquids capable of dissolving gold is aqua regia.

Aqua regia is a highly corrosive mixture of concentrated nitric acid (HNO3) and hydrochloric acid (HCl). The mixture is typically composed of nitric acid and hydrochloric acid in a ratio of 1:3. Aqua regia is called "royal water" because of its ability to dissolve noble metals like gold and platinum, which are otherwise resistant to corrosion by individual acids.

The mechanism by which aqua regia dissolves gold involves the formation of gold chloride (AuCl4-) ions. The nitric acid oxidizes elemental gold (Au) to form gold(III) ions (Au3+), while the hydrochloric acid provides chloride ions (Cl-) to react with the gold ions, forming soluble gold chloride complexes.

While aqua regia is one of the few liquids capable of dissolving gold, it is important to note that it is highly corrosive, reactive, and dangerous. It must be handled with extreme caution, and appropriate safety measures must be taken when working with it.

Aside from aqua regia, there are other specialized chemicals and processes that can dissolve gold, such as cyanide leaching in gold mining operations. However, these methods are not suitable for general laboratory or practical use due to their toxicity, environmental hazards, and specialized handling requirements.