Aqua regia

Aqua regia is a highly corrosive, fuming yellow or red solution, also known as royal water. It is a mixture of nitric acid and hydrochloric acid, optimally in a molar ratio of 1:3 respectively. Aqua regia is primarily used to dissolve noble metals such as gold, platinum, and palladium.

History

The term "aqua regia" was coined by alchemists during the Middle Ages. The name "royal water" was given due to its ability to dissolve the so-called "royal" or noble metals, which are resistant to most acids.

Composition and reactions

Aqua regia is formed by mixing one part of nitric acid and three parts of hydrochloric acid. The reaction between nitric acid and hydrochloric acid results in the formation of a mixture of nitrosyl chloride, chlorine, and water.

Uses

Aqua regia is primarily used in the recovery and purification of precious metals. It can dissolve gold, and is used in the extraction and purification of this metal from ores or recycled materials. The gold is typically precipitated out of the solution with a reducing agent.

Safety

Due to its highly corrosive nature, aqua regia must be handled with care. It can cause burns and is harmful if inhaled. It is also capable of reacting violently with certain chemicals and metals.

See also

• Acid
• Gold refining
• Noble metal

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