Nitric acid

Nitric acid

Nitric acid is an inorganic compound with the formula HNO₃. It is a highly corrosive mineral acid, meaning it can damage living tissue and other materials if it touches them. Pure nitric acid is colorless, but it often looks yellow because it breaks down over time into oxides of nitrogen.

Most nitric acid used in industry is about 68% mixed with water. When the amount of acid becomes stronger than 86%, it is called fuming nitric acid. Depending on how much nitrogen dioxide it contains, fuming nitric acid can be red fuming nitric acid or white fuming nitric acid.

Nitric acid is very important in chemistry. It helps add a nitro group to other molecules in a process called nitration. Some of these nitro compounds are used to make dyes and medicines, like metronidazole. Others are used in making explosives.

Nitric acid is also a strong strong oxidizing agent. This means it helps other materials change in useful ways during chemical reactions. Because of these helpful properties, nitric acid is used in many places, from making everyday products to helping with scientific research.

History

Nitric acid was first written about in old books from the 13th century. Some think it was known even earlier in Arabic works. Over time, scientists found better ways to make it.

In the 1600s, a scientist named Johann Rudolf Glauber learned how to make nitric acid by mixing two other substances. Later, Antoine Lavoisier and Henry Cavendish studied how it forms in nature. Today, most nitric acid is made from a process that uses ammonia. This process was created after scientists learned how to make ammonia more easily.

Physical and chemical properties

Nitric acid is a strong acid used in labs and factories. When mixed with water, it forms a special mix called an azeotrope, which boils at a specific temperature. Pure nitric acid is colorless, but it often turns yellow because it breaks down and creates gases.

There are different types of nitric acid. Some have extra gases mixed in, which can change their color and properties. These types are used in making important chemicals. The acid can also be very pure, almost without any water, and it stays clear but can turn yellow if it breaks down. It needs special care to keep it safe because it can react with light and heat.

Reactions

Nitric acid is a strong acid. This means it easily gives away a small part called a hydrogen ion. It can also act differently when it meets a stronger acid, like sulfuric acid.

When nitric acid touches some metals like magnesium, manganese, and zinc, it makes hydrogen gas. With other metals like copper and silver, it makes different substances. This depends on how strong the acid is and how hot it is. Some metals, such as chromium and aluminum, protect themselves. They form a layer that stops the acid from harming them.

Nitric acid can also react with things that are not metals and with organic materials. Sometimes this can create substances that can explode. It can also change proteins to a yellow color. This color change is a way scientists find proteins.

Production

Nitric acid is made using a process called the Ostwald process. This process uses ammonia and oxygen from the air to create nitric acid. First, ammonia burns to form a gas called nitric oxide. This gas is then mixed with oxygen from the air to form nitrogen dioxide. Finally, nitrogen dioxide is mixed with water to make nitric acid.

In labs, scientists can also make nitric acid by mixing nitrate salts with sulfuric acid and then distilling the mixture. This process is similar to the industrial method but done on a smaller scale.

Uses

Nitric acid is mostly used to make fertilizers. It is mixed with ammonia to create ammonium nitrate, which helps plants grow. This use takes up most of the nitric acid made each year.

Nitric acid is also used to make explosives and other chemicals. It can add a special group to different compounds, which helps create new materials. For example, it is used to make TNT and nylon and other important substances.

Safety

Nitric acid is a corrosive acid and a strong oxidizing agent. It can hurt skin and cause chemical burns because it breaks down proteins and fats in living tissue.

If nitric acid touches your skin, rinse it off with lots of water for at least 10–15 minutes. Take off any clothing that has acid on it and keep washing the skin. Nitric acid can also react in unsafe ways with many other materials.