Nitric Acid: Uses, Oxidising Hazards and SDS Requirements

Nitric acid (HNO3, CAS 7697-37-2) is a colourless to pale yellow liquid that is a strong acid and a strong oxidising agent at the same time. That combination makes it more demanding to store and ship than an acid that is merely corrosive. Commercial grades range from about 50 to 70 percent, with fuming grades above 90 percent used in specialist applications.

Typical uses

• Fertilisers, the main outlet, as the feedstock for ammonium nitrate and calcium ammonium nitrate.
• Explosives manufacture, as a nitrating agent for nitrocellulose, nitroglycerin and TNT.
• Metal treatment: pickling and passivating stainless steel, etching and cleaning, and dissolving silver and copper.
• Chemical synthesis of nylon precursors (adipic acid), dyes and pharmaceuticals.
• Laboratory analysis and sample preparation, where high-purity grades are used for trace-metal work.
• Electronics and semiconductor cleaning with ultra-pure grades.

GHS classification

Nitric acid is classified as an oxidising liquid (category 3, H272: may intensify fire), as causing severe skin burns and eye damage (category 1A, H314) and, in many entries, corrosive to metals (H290). Concentrated and fuming grades can also carry acute inhalation toxicity because of nitrogen oxide fumes. The signal word is Danger and the pictograms are flame over circle (GHS03) and corrosion (GHS05). EU suppliers often add the supplemental statement EUH071, corrosive to the respiratory tract. Always check the current harmonised entry, since concentration thresholds change the label for diluted products.

Why the oxidising property matters

An oxidiser supplies oxygen to a fire. Nitric acid can ignite or violently react with organic materials such as wood, paper, solvents, turpentine and oils, and with reducing agents, metal powders and carbides. A spill soaked up with sawdust is a classic fire cause. Section 6 of your SDS should say to use inert absorbents such as sand or vermiculite, and never combustible material.

Nitric acid also releases brown nitrogen dioxide fumes when it reacts with metals or decomposes, and these are toxic when inhaled and can cause delayed lung injury. Make sure Section 8 recommends ventilation and Section 4 warns that symptoms can be delayed for hours after exposure.

Storage

Use containers made from compatible materials such as stainless steel (for suitable concentrations), aluminium for concentrated acid, or fluoropolymer and glass. Vent them properly, store out of direct sunlight, and keep nitric acid away from organics, solvents, bases, metals, hydrazines, and reactive chemicals such as acetone. Do not store with ordinary corrosives like hydrochloric acid in the same bund, because a leak can release chlorine-bearing gases. Our storage compatibility guide provides a practical segregation scheme.

Transport and labelling

Nitric acid has its own transport entries, with different treatment for solutions below and above about 70 percent and for red fuming acid, and it usually carries both Class 8 and a subsidiary oxidiser hazard. Check the current UN number, subsidiary risk label and packing group for your specific concentration. Your label should show both pictograms, the signal word and the hazard and precautionary statements. See the harmonised data we hold on the nitric acid page, and compare with our guide to sulfuric acid.