Nitric acid

CAS: 7697-37-2

Chemical formula: HNO3

Properties

Colorless or yellow fuming liquid with a suffocating odor. Forms a yellow to brownish-red mist in the air. Can miscible with water arbitrarily. Relative density L 503 l melting point -42 ℃, boiling point 83 ℃. Nitric acid is not stable, when exposed to light or heat will decompose and release nitrogen dioxide, thus showing a light yellow color. Concentrated nitric acid is a strong oxidizing agent, can cause combustion when encountering organic matter, wood chips, etc.. Concentrated nitric acid containing traces of oxides can react with almost all metals except aluminum and chromium-containing special steel, while aluminum and chromium-containing special steel can be passivated by concentrated nitric acid. The reaction with ethanol, turpentine, coke and organic slag is very violent.

Preparation method

Use platinum as catalyst, oxidize ammonia to nitric oxide, then use air and concentrated nitric acid to oxidize all to ammonia dioxide, then use concentrated nitric acid to absorb, generate fuming nitric acid, then after desorption and stay.

Uses

Nitric acid belongs to strong oxidizing acid, and it has corrosive effect on most metals. High concentration of nitric acid has passivation effect on metals. Nitric acid is used to clean carbon steel, stainless steel, copper, brass, carbon steel a stainless steel composed of equipment, can remove scale, rust, a-Fez 03 and magnetic Fe3 04 have good solvency. In the biological method of sewage treatment process, it can be used as a source of nitrogen in the microbial nutrients and so on. In addition, nitric acid is widely used in the manufacture of fertilizers, chemical fibers, medicine, dyestuffs, rubber, etc. It is also an indispensable and important analytical chemical reagent in the national defense industry, metallurgical industry, printing and dyeing industry as well as other industrial sectors.

Safety

Nitric acid is toxic and ingestion will burn and corrode the mouth, esophagus and stomach, resulting in chest tenderness, shock and death. Prolonged exposure to nitric acid vapor can cause chronic bronchitis and chemical pneumonia. Therefore, protection should be taken when contacting and using nitric acid to avoid nitric acid or its vapors from entering the body. The maximum permissible concentration of nitric acid in air is 5 mg/ms, and it should not be stored and transported together with organic materials, oxidizing agents, flammable materials, strong alkalis, calcium carbide, metal powder, etc.