Nitric acid: properties, production and applications

Nitric acid (HNO₃) is a strong monobasic inorganic acid and one of the most important and large-tonnage products of the modern chemical industry. It is one of the six major inorganic acids and occupies a key position in the production of mineral fertilizers, explosives, dyes, plastics and many other products. Global nitric acid production is measured in tens of millions of tonnes per year, and its economic importance is comparable to that of sulfuric and phosphoric acids.

Physicochemical Properties

Anhydrous nitric acid is a colourless, low-boiling liquid with a pungent irritating odour. The density of anhydrous HNO₃ is 1513 kg/m³, its melting point is minus 41.59 °C, and its boiling point is 82.6 °C (with partial decomposition). Nitric acid is miscible with water in all proportions, forming an azeotropic mixture with a HNO₃ mass fraction of 68.4% and a boiling point of 120.7 °C. In aqueous solutions, it almost completely dissociates, making it one of the strongest mineral acids.

Concentrated nitric acid is unstable: when heated or exposed to light, it decomposes with the release of nitrogen dioxide NO₂, which colours the liquid yellow, and at high concentrations — red. This property gives "fuming" nitric acid its characteristic appearance and odour. Nitric acid is a strong oxidising agent: it reacts with most metals (except zirconium, niobium, rhodium, tantalum, iridium, platinum and gold), oxidises sulfur to sulfuric acid, phosphorus to phosphoric acid, and organic compounds through nitration or oxidation. Some metals, such as aluminium and iron, which readily dissolve in dilute acid, are resistant to concentrated HNO₃ due to the formation of a sparingly soluble oxide film (passivation).

A mixture of concentrated nitric and hydrochloric acids in a volume ratio of 1:3 is known as "aqua regia" and is capable of dissolving gold and platinum metals. A mixture of 100% HNO₃ and 96% H₂SO₄ in a 9:1 ratio is called melange. Salts of nitric acid — nitrates — are widely used as fertilizers and oxidising agents.

Production Technology

Modern industrial nitric acid production is based on the catalytic oxidation of ammonia with atmospheric oxygen — the Ostwald process, developed in the early 20th century. The process includes three main stages.

In the first stage, ammonia is oxidised to nitrogen monoxide NO on a platinum-rhodium catalyst gauze at a temperature of about 800–900 °C. In the second stage, NO is oxidised to nitrogen dioxide NO₂ by atmospheric oxygen in the gas phase. In the third stage, NO₂ is absorbed by water in absorption columns to form nitric acid. Depending on the process scheme, dilute (55–58%) or concentrated (up to 98%) acid is obtained. To produce concentrated HNO₃, methods of dehydrating dilute acid with sulfuric acid or extractive distillation are used.

In Russia, requirements for concentrated nitric acid are regulated by GOST 701-89. The standard applies to acid produced by direct synthesis and provides for two grades: grade A is intended for the electronic and radio-electronic industry and nitration processes, grade B — for galvanic works and other technical purposes.

Applications

Nitric acid finds wide application in various industries. The main consumer is mineral fertilizer production: this segment accounts for about 80% of global HNO₃ consumption. Nitric acid is used to produce ammonium nitrate, calcium nitrate, complex fertilizers (NPK) and other nitrogen-containing products.

In the chemical industry, nitric acid serves as a feedstock for the production of explosives (nitroglycerin, TNT, HMX), nitro compounds, dyes, pharmaceuticals, synthetic fibres and plastics. It is used in the nitration of organic compounds, in the production of adipic acid (a nylon feedstock) and toluene diisocyanate (TDI). In metallurgy, nitric acid is used for pickling and cleaning metals; in hydrometallurgy — for opening ores and extracting non-ferrous and rare metals. In the electronics industry, it is used for surface cleaning and etching of semiconductor materials.

Global Production and Market

The global nitric acid market demonstrates steady growth. According to Fortune Business Insights, the market was valued at USD 30.84 billion in 2025, projected to reach USD 31.97 billion in 2026 and USD 39.53 billion by 2034 at a CAGR of 2.80%. In physical terms, the market volume in 2025 was 69.36 million tonnes, and by 2031 it is projected to grow to 82.66 million tonnes. According to other estimates, the market was valued at USD 31.50 billion in 2025 and is expected to reach USD 43.74 billion by 2032 at a CAGR of 4.8%.

The Asia-Pacific region is the largest nitric acid market: in 2025, its share was 51% of global volume. China remains the largest producer and consumer, driven by large-scale fertilizer production and chemical industry development. Europe accounts for about 19% of the market, North America — 15%. Key market growth drivers are increasing demand for nitrogen fertilizers, the development of the automotive industry (production of adipic acid and polyurethanes), and the expansion of nitric acid applications in electronics and metallurgy.

Production in Russia

Russia possesses significant nitric acid production capacities. The largest producer is Acron PJSC, whose Novgorod site operates 10 nitric acid units with a total design capacity of 1.8 million tonnes per year. In 2025, nitric acid output at the enterprise exceeded 2 million tonnes in monohydrate. In January 2026, a new production record was set — 184,000 tonnes of nitric acid in one month.

Other major producers include the Azot branch of Uralchem in Berezniki, Dorogobuzh PJSC, SDS Azot JSC and other enterprises. Concentrated nitric acid production in Russia in 2025 reached 139,246 tonnes, up 32.2% from the previous year. The main production centre was the Volga Federal District with a 65.8% share.

Safety and Storage

Nitric acid is a corrosive and hazardous substance belonging to hazard class 3 (moderately hazardous substances). Concentrated HNO₃ causes severe chemical burns on contact with skin. Nitric acid vapours and nitrogen oxides irritate the upper respiratory tract, cause conjunctivitis and damage the cornea. When working with nitric acid, personal protective equipment must be used: acid-resistant gloves, protective goggles or face shields, an apron, and effective ventilation must be provided.

Nitric acid must be stored in tightly closed containers made of acid-resistant materials, in a cool, dry, well-ventilated area, away from combustible substances, reducing agents, bases and organic materials. When mixing with water, the acid must be added to the water, not vice versa, to avoid a violent exothermic reaction and splashing.

Conclusion

Nitric acid remains one of the key products of the global chemical industry, providing for the production of fertilizers, explosives, polymers, dyes and many other products. Growing demand for nitrogen fertilizers, the development of the automotive industry and electronics are creating sustained demand for this essential chemical. Russia, possessing significant production capacities and implementing modernisation projects, maintains its position as one of the leading players in the global nitric acid market.