Generally, nitric acid solution above 8mol/L is called concentrated nitric acid.The mass fraction of commercial concentrated nitric acid is about 68%.When nitric acid is miscible with watersulphuric acidSimilar will release a lot of heat, so it needs to be stirred constantly, and concentrated nitric acid can only be added to water, not the other way around.Nitric acid with concentration above 98% is called“Fuming nitric acid”。
1. Nitric acid is a strong acid and has the common property of acid.
2. Both concentrated and dilute nitric acid have strong oxidizability. The higher the concentration, the stronger the oxidizability.
3. Nitric acid is a volatile acid. The higher the concentration, the more volatile. Nitric acid with a concentration of more than 98% is called‘Fuming nitric acid’。
4. Nitric acid is unstable and will decompose when exposed to light or heat.
5. Nitric acid has strong corrosivity, which not only corrodes skin, but also rubber.
6. Vapor is strongly irritating to mucous membrane and skin of eyes, respiratory tract, etc.High vapor concentration can cause pulmonary edema.Corrosive to teeth.Skin contact can cause burns, corrosion and scars, and concentrated nitric acid corrosion can reach a considerable depth.If it enters the pharynx, it may cause severe corrosive burns to the digestive tract below the oral cavity, and even cause shock and death in severe cases.People below 30mg/mthreeThere is no obvious damage at left and right.Inhalation can cause pneumonia.[1]
Storage method
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Concentrated nitric acid will decompose into nitrogen dioxide and become yellow under light. Therefore, concentrated nitric acid is often placed in a brown reagent bottle in the shade.
Identify concentrated nitric acid and dilute nitric acid
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1. Add iron or aluminum into cold nitric acid. If there is no obvious phenomenon, it is concentrated nitric acid. If bubbles appear on the surface of iron or aluminum, it is dilute nitric acid.
2. Directly, thick nitric acid is exposed to white fog, and dilute nitric acid is exposed to no white fog. Here, the volatility of nitric acid is utilized.
nature
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Instability
Concentrated nitric acid will decompose under lightNitrogen dioxideBecause it is yellow, concentrated nitric acid is often placed in a brown reagent bottle in the shade.
Strong oxidation
1. React with most metals
2. React with nonmetals
In the reaction, non-metal is oxidized to the highest valence oxide or its correspondingOxyacid。
3. Passivation of aluminum and iron
Cold concentrated nitric acid can passivate iron and aluminum.Hot concentrated nitric acid will not passivate it.
Danger and strong acidity
Hazard: It decomposes when heated, producing toxic smoke;Strong oxidant, which will react violently with combustible and reducing substances and explode.Strongly acidic, it reacts violently with alkali, corrodes most metals (except aluminum and its alloys), generates nitrogen oxides, and reacts violently with many commonly used organic substances, causing fire and explosion hazards.[2]
Safety measures
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1. Do not breathe smoke, vapor, or spray.
2. In case of contact with eyes or skin, immediately wash with plenty of water and seek medical treatment as soon as possible.
3. All contaminated clothing must be removed immediately.
4. Wear appropriate protective clothing, gloves and masks.
5. When storing concentrated nitric acid, it should be separated from reducing substances.
