Aqua Regia: Properties of Aqua Regia, Applications of Aqua Regia, Advantages of Aqua Regia, Disadvantages of Aqua Regia

Aqua Regia

Aqua regia is a mixture of nitric acid and hydrochloric acid, typically in a 3:1 ratio. It is a highly corrosive and powerful oxidizing agent that can dissolve gold and other noble metals, making it useful for extracting and purifying these metals in laboratory settings. It is also used in the production of chloroauric acid, a precursor to the synthesis of gold compounds. However, due to its corrosive nature, it must be handled with extreme caution.

Aqua regia is a Latin term that means “royal water”, which is a reference to its ability to dissolve the “royal” metal gold. It is a clear, yellow-orange liquid that has a strong, pungent smell and generates a great deal of heat when mixed. It should be handled with gloves, goggles and lab coat to protect the user from corrosive effect.

Reactions of Aqua Regia: Properties of Aqua Regia, Applications of Aqua Regia, Advantages of Aqua Regia, Disadvantages of Aqua Regia


It is typically made by mixing concentrated nitric acid and hydrochloric acid in a 3:1 ratio, but the exact ratio can vary depending on the specific application and the types of impurities present in the sample. Aqua regia can dissolve not only gold but also other metals such as platinum, palladium and rhodium, as well as some forms of base metals like copper and nickel.

The process of using aqua regia to extract gold is known as “gold refining.” It involves dissolving the gold-containing material in aqua regia, and then carefully separating and purifying the gold from the other dissolved metals. However, the process is not suitable for gold alloys with high silver content and it should be used only with pure gold. Aqua regia is also used in the production of chloroauric acid, a precursor to the synthesis of gold compounds used in certain industrial processes, such as the production of electronic components.

It is important to note that aqua regia is highly toxic and should be handled with extreme care. It is important to neutralize the remaining solution after use, to avoid environmental pollution.

In addition to its use in gold refining and the production of chloroauric acid, aqua regia has a number of other applications in the laboratory and in industry. For example, it can be used to dissolve and analyze certain types of rocks and minerals, as well as for the preparation of certain types of organometallic compounds used in research.

Aqua regia can also be used to dissolve and purify other metals, such as silver and palladium. In metallurgy, it is used to clean and purify scrap metal before it is recycled.

It is also used in the field of analytical chemistry to determine the presence of gold and other precious metals in samples. The method is called Aqua regia Digestion, where a small amount of sample is digested with aqua regia, then the solution is analyzed by various techniques like ICP-OES, AAS, etc.

It should be handled with extreme care, as it is highly corrosive and can cause severe burns and other injuries if it comes into contact with skin or eyes. It should be stored in a cool, well-ventilated area, away from any sources of ignition or heat, and should be disposed of properly in accordance with local regulations.

It is important to mention that Aqua Regia should not be heated as it releases toxic fumes, such as chlorine gas and nitrogen oxides. It should be handled in a fume hood and also it is important to have a proper ventilation system in place.

Properties of Aqua Regia

Aqua regia is a mixture of nitric acid (HNO3) and hydrochloric acid (HCl) in a 3:1 ratio, although the exact ratio can vary depending on the specific application. Some of the properties of aqua regia include:

  • Corrosiveness: Aqua regia is a highly corrosive and powerful oxidizing agent that can cause severe burns and other injuries if it comes into contact with skin or eyes.
  • Appearance: It is a clear, yellow-orange liquid that has a strong, pungent smell.
  • Reactivity: Aqua regia is reactive and can generate a great deal of heat when mixed.
  • Solubility: It can dissolve gold and other noble metals, as well as some forms of base metals like copper and nickel.
  • Toxicity: Aqua regia is toxic and should be handled with extreme care. It should be stored in a cool, well-ventilated area, away from any sources of ignition or heat, and should be disposed of properly in accordance with local regulations.
  • Decomposition: Aqua regia should not be heated as it releases toxic fumes, such as chlorine gas and nitrogen oxides.
  • Acidic strength: The mixture has a pH of less than 1, meaning it is highly acidic.
  • Boiling Point: The boiling point of Aqua Regia is around 120 °C
  • Density: The density of Aqua Regia is around 1.4 g/cm3
  • Explosive: Aqua regia is explosive when it comes into contact with organic matter.

It is important to note that these properties may vary depending on the specific composition of the aqua regia mixture and the impurities present in the solution.

Applications of Aqua Regia

Aqua regia is a powerful and versatile chemical mixture that has a wide range of applications in the laboratory and in industry. Some of the main applications of aqua regia include:

  • Gold refining: Aqua regia is commonly used to extract and purify gold in laboratory settings. The process involves dissolving the gold-containing material in aqua regia, and then carefully separating and purifying the gold from the other dissolved metals.
  • Production of chloroauric acid: Aqua regia is used in the production of chloroauric acid, which is a precursor to the synthesis of gold compounds used in certain industrial processes, such as the production of electronic components.
  • Analysis of rocks and minerals: Aqua regia can be used to dissolve and analyze certain types of rocks and minerals, as well as for the preparation of certain types of organometallic compounds used in research.
  • Silver and palladium refining: Aqua regia can also be used to dissolve and purify other metals, such as silver and palladium.
  • Metallurgy: It is used to clean and purify scrap metal before it is recycled.
  • Analytical chemistry: It is used in the field of analytical chemistry to determine the presence of gold and other precious metals in samples.
  • PCB etching: Aqua regia is also used in the PCB etching process, where it is used to remove copper from PCB boards.

It is important to remember that Aqua regia should be handled with extreme care, as it is highly corrosive and toxic. It should be stored in a cool, well-ventilated area, away from any sources of ignition or heat, and should be disposed of properly in accordance with local regulations.

Advantages of Aqua Regia

Aqua regia is a powerful and versatile chemical mixture that has several advantages, some of which include:

  • High efficiency: Aqua regia is highly effective at dissolving and purifying gold and other precious metals, making it an efficient method for gold refining and purification.
  • Versatility: Aqua regia can be used to dissolve a wide range of metals, including gold, silver, palladium, and other noble metals, as well as some forms of base metals like copper and nickel.
  • Low cost: Aqua regia is relatively inexpensive to produce and use, making it an affordable option for many industrial and laboratory applications.
  • High purity: Aqua regia is capable of producing high-purity gold and other metals, making it suitable for use in electronic and other precision applications.
  • Wide availability: Aqua regia is widely available and used in many laboratories and industries around the world.
  • Easy to use: Aqua regia is easy to use and handle, and it is not necessary to have special equipment or facilities to use it.

It is important to remember that Aqua regia should be handled with extreme care, as it is highly corrosive and toxic. It should be stored in a cool, well-ventilated area, away from any sources of ignition or heat, and should be disposed of properly in accordance with local regulations.

Disadvantages of Aqua Regia


Aqua regia is a powerful and versatile chemical mixture, but it also has several disadvantages, some of which include:

  • High toxicity and corrosiveness: Aqua regia is highly toxic and corrosive, making it dangerous to handle and store. It can cause severe burns, respiratory problems, and other health issues if it comes into contact with skin or eyes.
  • Explosive: Aqua regia is explosive when it comes into contact with organic matter, which increases the risk of accidents and injuries.
  • Decomposition: Aqua regia should not be heated as it releases toxic fumes, such as chlorine gas and nitrogen oxides.
  • Environmental hazard: Aqua regia is a hazardous waste and should be disposed of properly in accordance with local regulations. Improper disposal can harm the environment and the health of living organisms.
  • Requires special handling: Aqua regia should be handled with extreme care, as it is highly corrosive and toxic. It should be stored in a cool, well-ventilated area, away from any sources of ignition or heat.
  • Risk of contamination: Aqua regia can be contaminated easily, which can lead to an inaccurate analysis or poor quality of the final product.
  • Limited application: Aqua regia is not suitable for dissolving all types of metals and minerals and is not recommended for use in certain applications.

In summary, Aqua regia should be used with care and only by trained professionals. It has to be handled with proper protective equipment, proper storage and disposal, and used in well-ventilated areas to minimize the risk of accidents and injuries.

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