Aqua regia

This is a special liquid.

It is made by mixing two strong liquids. When they mix, the liquid turns orange.

Most liquids cannot melt gold. But this liquid can! It can even melt platinum. This helps people make very pure gold. It can also clean glass in a lab. Scientists must be very careful with it. It is a very strong liquid.

It can be dangerous if not used right.

Aqua regia is a very strong liquid. Its name means "royal water" in Latin.

It is made by mixing two acids. These are nitric acid and hydrochloric acid. When they mix, the liquid changes color. It starts clear. Then it turns yellow, orange, or red in seconds.

This happens because of gases that form in the mix.

Most acids cannot dissolve noble metals. These are metals like gold and platinum. But aqua regia can dissolve them! This makes it very useful. Scientists use it to make very pure gold. It can also clean glass in labs.

It is better than other cleaners for some glass.

This liquid must be used right away. It loses its power quickly as gases escape. It is also very dangerous. It can cause explosions if handled poorly. During World War II, a scientist used it to hide gold. He dissolved Nobel Prize medals in the liquid. The Nazis did not notice the gold in the lab. After the war, the gold was recovered and remade.

Aqua regia is a very strong liquid used by scientists. Its name comes from Latin and means "royal water."

This liquid is special because it can dissolve noble metals. These are metals like gold and platinum that usually do not react with other things. Most acids cannot break these metals down. However, aqua regia is powerful enough to turn solid gold into a liquid.

This makes it a very important tool for chemistry.

To make this liquid, you mix two different acids together. You use concentrated nitric acid and concentrated hydrochloric acid. The best mix uses a ratio of one part nitric acid to three parts hydrochloric acid.

When they mix, a chemical reaction happens right away. This reaction creates gases like nitrosyl chloride and chlorine gas. Because of these gases, the liquid starts to fume. It also changes color from clear to yellow, orange, or red within seconds. As the gases escape, the liquid loses its strength. This is why scientists usually mix it right before they need to use it.

People have known about this liquid for a very long time. Records from 660 AD show that nitrate was used to make it. In Europe, it appeared in old books written by people like pseudo-Geber. Early alchemists used it to work with gold. They even used art to describe it. One old drawing shows a fox eating a rooster. The rooster represents gold, and the fox represents the aqua regia. This shows how much they wondered about its power.

Today, aqua regia has many important jobs in science. It is used in the Wohlwill process to make very pure gold. This process can make gold that is 99.999% pure.

Scientists also use it to clean glassware in laboratories. It is great for cleaning NMR tubes because it leaves no metal traces behind. It can even help find new metals. When scientists used it on platinum, they discovered two very dense metals called iridium and osmium. These metals did not dissolve and stayed at the bottom of the container.

This liquid has even played a part in world history. During World War II, a chemist named George de Hevesy used it to hide treasure. He dissolved two gold Nobel Prize medals in aqua regia. He did this so the Nazis would not take them. He put the liquid on a shelf in his lab. The soldiers did not realize the gold was hidden in the jar. After the war ended, de Hevesy recovered the gold from the acid. The medals were then remade and given to the winners again.

Aqua regia is a highly corrosive liquid mixture used in chemistry. Its name comes from Latin, meaning "regal water" or "royal water."

This name was given by alchemists because the liquid can dissolve noble metals. Noble metals, such as gold and platinum, are very stable and do not react with most other substances. Aqua regia is unique because it can break these metals down into a liquid form. This ability makes it a vital tool for refining precious metals and cleaning laboratory equipment.

To create aqua regia, scientists mix concentrated nitric acid with concentrated hydrochloric acid. The most effective mixture uses a molar ratio of 1:3. This means there are three parts hydrochloric acid for every one part nitric acid.

When these two acids combine, a rapid chemical reaction occurs. This reaction produces volatile gases known as nitrosyl chloride and chlorine gas. Because these gases are released, the liquid is described as "fuming." The mixture also undergoes a rapid color change. It starts as a colorless liquid but quickly turns yellow, orange, or red. As the gases escape the solution, the aqua regia loses its potency. For this reason, scientists usually prepare it immediately before they use it.

The way aqua regia dissolves gold is a multi-step chemical process. Neither acid can dissolve gold on its own. First, the nitric acid acts as a powerful oxidizer. It dissolves a very small amount of gold to create gold(III) ions. Next, the hydrochloric acid provides a steady supply of chloride ions. These chloride ions react with the gold ions to produce tetrachloroaurate(III) anions. This reaction is an equilibrium reaction that favors the formation of these anions. By pulling the gold ions into the solution, the acid allows even more gold to be oxidized. Eventually, the solid gold turns into a liquid called chloroauric acid.

Dissolving platinum with aqua regia is a much more complex process than dissolving gold. The initial reaction produces a mixture of chloroplatinous acid and nitrosoplatinic chloride. The nitrosoplatinic chloride is a solid product that does not stay in the liquid. To achieve full dissolution, scientists must perform repeated extractions using concentrated hydrochloric acid. They can also oxidize the chloroplatinous acid into chloroplatinic acid. This is done by saturating the solution with molecular chlorine while applying heat. This complex chemistry was useful for historical discoveries. When scientists used aqua regia on platinum ores, they discovered iridium and osmium. These two metals are extremely dense and did not dissolve. Instead, they collected as an insoluble metallic powder at the bottom of the vessel.

History shows that humans have used these types of mixtures for centuries. Records from 660 AD suggest that nitrates were used to create similar substances. In Europe, aqua regia appeared in writings by pseudo-Geber. Early alchemists used symbolic art to explain its power. One famous illustration from 1678 shows a fox eating a rooster.

In this symbol, the rooster represents gold and the fox represents aqua regia. This imagery captured the intense chemical struggle between the metal and the acid. Later, in 1789, the chemist Antoine Lavoisier referred to the substance as nitro-muriatic acid.

Today, aqua regia serves several critical roles in modern science and industry. One primary use is the Wohlwill process, which is used to refine gold. This process uses chloroauric acid as an electrolyte to produce gold with a purity of 99.999%. It is also used for etching and in various analytic procedures. In laboratories, it is a preferred method for cleaning glassware, such as NMR tubes. While other methods like chromic acid baths exist, they are highly toxic and can cause explosions. Aqua regia is also safer for certain types of spectroscopy because it leaves no paramagnetic chromium traces behind. However, it remains very corrosive and can cause explosions if mishandled.

Aqua regia has even played a role in protecting scientific history during wartime. During World War II, chemist George de Hevesy used the liquid to hide gold Nobel Prize medals. He dissolved the medals belonging to Max von Laue and James Franck into the acid. He placed the solution on a laboratory shelf in Denmark to hide it from the Nazis. The soldiers did not realize the gold was hidden in a common chemical jar. After the war, de Hevesy successfully precipitated the gold out of the solution. The gold was used to recast the medals, which were then returned to the original winners.