What Is Nitric Acid?
Nitric acid, represented by the chemical formula HNO3, is a widely recognized strong acid. It poses significant hazards upon contact, capable of damaging skin, the digestive tract, and the respiratory system, necessitating careful handling.
Uses of Nitric Acid
Nitric acid’s applications span across various sectors such as agriculture, construction, military, industry, textiles, chemistry, and pharmaceuticals:
1. Fertilizer Production
As a critical nitrogen source, nitric acid is fundamental in creating fertilizers, alongside phosphoric acid and potassium, to enhance plant growth.
2. Explosive Materials
It is essential in synthesizing explosives like nitroglycerin, nitrocellulose, TNT, and picric acid, and serves as an oxidizing agent in rocket propellants due to its rapid decomposition with amines.
3. Miscellaneous Uses
Additionally, nitric acid is utilized in producing celluloid, dyes, pigments, electroplating solutions, dissolving metals, pharmaceuticals, synthetic fibers, toluene diisocyanate (for polyurethane), and adipic acid.
Properties of Nitric Acid
A colorless liquid with a molecular weight of 63.02 and a specific gravity of 1.502, nitric acid exhibits a light yellow tint and peculiar odor, fuming when exposed to air. It’s a potent acid and oxidizer, reacting aggressively with bases, decomposing under light, and corroding most metals except gold and platinum. Iron, chromium, and aluminum exhibit passivity against it. When heated, it decomposes, emitting toxic fumes and posing risks of violent reactions with flammable or reducing substances and organic compounds.
Other Information on Nitric Acid
Nitric Acid Production Methods
Nitric acid production predominantly employs the ammonia oxidation method (Ostwald process), consisting of ammonia oxidation to nitric oxide, nitric oxide oxidation to nitrogen dioxide, and nitrogen dioxide absorption in water:
1. Oxidation of Ammonia: Ammonia gas mixed with air passes through a platinum-rhodium catalyst, converting to nitrogen monoxide and water in an exothermic reaction with high yield.
2. Oxidation of Nitric Oxide: The nitric oxide is further oxidized to nitrogen dioxide, a step that benefits from the cooling process’s waste heat.
3. Absorption of Nitrogen Dioxide: Nitrogen dioxide reacts with water to produce nitric acid and nitric oxide, typically yielding 55-68% nitric acid, known as dilute nitric acid.
To concentrate nitric acid beyond 68%, water is removed by heating or using a dehydrating agent, overcoming azeotropic limitations.