Nitric acid turns up in an unexpectedly wide range of places, from the bag of fertilizer in your garden shed to the plume drifting from an active volcano. Industrially, it is one of the most heavily produced chemicals on the planet, consumed primarily in making nitrogen-based fertilizers but also in explosives, metal finishing, semiconductor fabrication, and cellulose-based materials. Nature generates it too, through volcanic emissions, lightning strikes, and microbial activity in soil. Understanding where nitric acid appears helps explain why it matters to agriculture, manufacturing, environmental science, and even space exploration.
Fertilizers Are the Biggest Consumer
The single largest use of nitric acid worldwide is the production of nitrogen fertilizers. Most of it goes into making ammonium nitrate, the white granular material spread across farm fields to boost crop yields. The process is straightforward in concept: nitric acid reacts with ammonia, and the result is ammonium nitrate. One industrial study investigating this reaction used a 64% nitric acid solution neutralized with 90% gaseous ammonia, reflecting the high-concentration inputs typical of commercial plants.1IOP Conference Series: Earth and Environmental Science. Determination the phase contact surface size of nitric acid with ammonia neutralization process for the ammonium nitrate production Calcium ammonium nitrate, potassium nitrate, and other specialty fertilizers also begin with nitric acid as a feedstock. If you have ever handled a bag of store-bought fertilizer labeled with a nitrogen-phosphorus-potassium ratio, there is a good chance the nitrogen component traces back to nitric acid somewhere in the supply chain.
Nearly all of this nitric acid is itself manufactured through the Ostwald process, a well-established industrial method that oxidizes ammonia over a platinum-rhodium catalyst to eventually yield nitric acid.2PubMed Central. Ostwald Process Intensification by Catalytic Oxidation of Nitric Oxide The scale is enormous: global production runs into tens of millions of metric tons per year, and fertilizer manufacturing accounts for the majority of that output. So when people ask what “has” nitric acid in it, the honest first answer is the agricultural supply chain. Fertilizer might not literally contain nitric acid on the shelf, but nitric acid is baked into its chemistry.
Explosives and Energetic Materials
After fertilizers, explosives are the next major destination. Nitric acid is a key ingredient in producing TNT, nitroglycerin, and a range of military and commercial explosives. The process involves nitration, where nitric acid (often mixed with sulfuric acid) introduces nitrogen-oxygen groups into organic molecules, making them highly energetic. Research on TNT synthesis, for instance, has shown that converting dinitrotoluene to trinitrotoluene traditionally requires highly concentrated nitric acid and oleum, though newer flow-chemistry methods have demonstrated that a mixture of ordinary 98% sulfuric acid and 65% nitric acid can achieve high-purity TNT with conversion rates suitable for military-grade specifications.3PubMed Central. Synthesis of 2,4,6-Trinitrotoluene (TNT) Using Flow Chemistry
Nitrocellulose is another product in this family. Made by treating cellulose fibers with a mixture of nitric and sulfuric acids, nitrocellulose shows up in gun propellants, lacquers, nail polish, and even some printing inks. Research comparing different cellulose sources has found that luffa cellulose, when nitrated at room temperature for 60 minutes using a 1:3 nitric-to-sulfuric acid ratio, produced nitrocellulose with a nitrogen content of about 13.7%, high enough for military-grade use.4PubMed Central. Selecting appropriate cellulose morphology to enhance the nitrogen content of nitrocellulose Separate work on wood-pulp-derived cellulose fibers has examined how the kinetics of nitration change with different acid mixtures and reaction conditions, confirming that the morphology and source of the cellulose influence the final product’s quality.5Industrial and Engineering Chemistry Research. Nitration Kinetics of Cellulose Fibers Derived from Wood Pulp in Mixed Acids
If you have ever handled old-fashioned photographic film, early plastic billiard balls, or certain theatrical flash paper, you have held a product descended from nitric acid. Even modern smokeless gunpowder is essentially nitrocellulose in a controlled form.
Metal Work, Gold Refining, and Cleaning Solutions
Nitric acid is a staple in metalworking shops and precious-metal refineries. Jewelers and assayers have used it for centuries to separate gold from silver in alloys, a technique called “gold parting.” An overview of this practice describes how nitric acid selectively dissolves silver while leaving gold behind, a principle that has also been adapted in modern nanotechnology for creating nanoporous gold materials.6Substantia. Gold parting with nitric acid in gold-silver alloys The classic test for gold purity, rubbing a piece against a touchstone and applying acid, relies on the same chemistry. Aqua regia, a mixture of nitric and hydrochloric acids, takes the concept a step further and dissolves gold itself, which is why it is used in refining and recycling precious metals.
Beyond precious metals, dilute nitric acid is commonly used to “passivate” stainless steel. The acid strips away free iron and contaminants from the surface, leaving behind a thin, protective chromium-oxide layer. You will find nitric acid listed on the safety data sheets of many industrial passivation and pickling solutions. It also appears in metal-etching formulas, cleaning agents for laboratory glassware, and some rust removers sold to hobbyists and machinists.
Semiconductor Fabrication and Electronics
The electronics industry uses nitric acid in ways most people never think about. Silicon wafers, the foundation of computer chips, are shaped and etched using acid mixtures. One well-studied combination is hydrofluoric acid, nitric acid, and acetic acid, often abbreviated HNA. Research on deep wet etching has investigated how this mixture carves large microcavities into silicon wafers, a step in manufacturing sensors, microelectromechanical systems, and other miniaturized devices.7Japanese Journal of Applied Physics. Deep Wet Etching in Hydrofluoric Acid, Nitric Acid, and Acetic Acid of Cavities in a Silicon Wafer In this context, nitric acid acts as the oxidizer: it oxidizes the silicon surface, and the hydrofluoric acid then dissolves the oxide. Without nitric acid, the etching would not proceed.
Printed circuit board manufacturing, solar cell production, and LED fabrication all involve similar acid-based etching and cleaning steps. If you are reading this on a phone or laptop, the processor inside it was almost certainly exposed to nitric acid at some point during its manufacture.
Pulp, Paper, and Wood Processing
Nitric acid has a niche but real role in the pulp and paper industry. Dilute nitric acid solutions can be used to break down lignin, the tough structural polymer that holds wood fibers together, in a process sometimes called nitric acid pulping. A study on birch wood found that cooking with about 9% nitric acid for a little over four hours at 85°C yielded roughly 51% pulp with a lignin content of about 5%.8BioResources. Study on the nitric acid pulping, delignification course, and waste-liquid recovery While this is not the dominant pulping method globally (sulfate and sulfite processes are far more common), nitric acid pulping has attracted interest because it can produce pulp under atmospheric pressure and at relatively low temperatures, and the waste liquor can be recovered.
This connects to the nitrocellulose discussion above. The quality of the cellulose going into the nitration step matters for the final product, and pulping is the upstream process that isolates those cellulose fibers in the first place.
Volcanoes as a Natural Source
Nature produces nitric acid without any human involvement, and volcanoes are one of the more surprising contributors. Research measuring the persistent plumes from four volcanoes, including Masaya in Nicaragua, Etna in Italy, and Villarrica and Lascar in Chile, found that near-source concentrations of nitric acid vapor ranged from about 1.8 to 5.6 micromoles per cubic meter. That is one to two orders of magnitude above background levels.9Earth and Planetary Science Letters. Nitric acid from volcanoes Before these measurements, volcanoes were rarely considered part of the global nitrogen cycle. The discovery added a new piece to the puzzle of how nitrogen moves through the atmosphere.
Volcanic lightning adds another layer. During large explosive eruptions, the intense electrical discharges within ash clouds can fix atmospheric nitrogen into nitrogen oxides, which then oxidize in the atmosphere to form nitrate. Geological evidence from deposits left by ancient caldera-forming eruptions in the Neogene period shows significant nitrate concentrations that correlate with sulfur and chlorine, species directly emitted by volcanoes. Multi-isotopic analysis confirmed these nitrates originated from the atmospheric oxidation of nitrogen oxides produced by volcanic lightning.10PubMed Central. Geological evidence of extensive N-fixation by volcanic lightning during very large explosive eruptions In other words, a powerful enough eruption generates its own nitric acid through a combination of heat, gas, and lightning.
The Atmosphere, Lightning, and Acid Rain
Even without volcanoes, nitric acid forms naturally in the atmosphere whenever nitrogen oxides react with water and oxygen. Ordinary lightning strikes produce nitrogen oxides from the nitrogen and oxygen in air, and those oxides eventually become nitric acid. Combustion engines and coal-fired power plants vastly amplify this process by releasing nitrogen oxides on a scale far beyond what natural lightning produces. The nitric acid that results dissolves in cloud droplets and falls as a component of acid rain.
The environmental effects have been studied extensively, particularly in the northeastern United States. Research on New York State’s forests and waterways found that acidic deposition, which includes both sulfuric and nitric acid components, has depleted nutrient minerals like calcium and magnesium from soils, mobilized toxic aluminum into soil solutions, and lowered the pH of lakes and streams. Red spruce lost essential calcium from their needles, making them more vulnerable to freezing damage, while sugar maples showed mortality linked to nutrient deficiencies compounded by insect damage or drought. Aquatic ecosystems suffered reduced diversity and abundance of species, and links emerged between acidification and mercury contamination in fish.11PubMed. Effects of acidic deposition on forest and aquatic ecosystems in New York State So while nitric acid is a useful industrial chemical, its presence in rainwater tells a different story.
Nitric Acid in the Upper Atmosphere and Polar Clouds
High above the Earth’s surface, nitric acid plays a role that most people have never heard of. In the polar stratosphere, it combines with water to form crystalline particles called nitric acid trihydrate, which make up a type of polar stratospheric cloud. These clouds are more than a curiosity: they provide surfaces on which chlorine-containing molecules become activated, accelerating the destruction of the ozone layer each polar winter and spring.
Understanding how these clouds form has been an active area of research. Satellite observations during the Arctic winter of 2009–2010 provided strong evidence that nitric acid trihydrate crystals do not only nucleate on pre-existing ice particles, as previously assumed. Instead, they can form through a different mechanism, likely involving tiny solid particles of meteoritic origin that act as seeds for crystal growth.12Atmospheric Chemistry and Physics. Heterogeneous formation of polar stratospheric clouds – Part 1: Nucleation of nitric acid trihydrate (NAT) Laboratory experiments confirmed that analogues for meteoric smoke particles immersed in nitric acid solution droplets can indeed nucleate crystalline nitric acid under polar stratospheric conditions, offering a plausible pathway for the cloud densities observed in the real atmosphere.13Atmospheric Chemistry and Physics. Nucleation of nitric acid hydrates in polar stratospheric clouds by meteoric material
Separate laboratory work examined whether pure nitric acid trihydrate droplets could freeze on their own at very low temperatures. The experiments found that nucleation does occur rapidly in the 163–167 Kelvin range, but the resulting crystals grow extremely slowly unless the temperature is then raised. The researchers concluded that this homogeneous freezing pathway is unlikely to be important for real polar stratospheric clouds, because the required temperatures are lower than those typically found in the lower stratosphere.14Journal of Geophysical Research: Atmospheres. The nucleation rate constants and freezing mechanism of nitric acid trihydrate aerosol under stratospheric conditions The meteoric-dust pathway, by contrast, works at higher, more realistic temperatures. This means that dust from disintegrating meteors, combined with nitric acid already present in the stratosphere, helps set the stage for ozone chemistry over the poles each year.
Soil Microbes and the Nitrogen Cycle
At ground level, nitric acid is part of the broader story of how nitrogen moves through soil. Nitrifying bacteria and archaea convert ammonium first into nitrite and then into nitrate, a process called nitrification. In acidic soils, this chemistry gets complicated. At low pH, the chemical equilibrium shifts so that nitrous acid (the protonated form of nitrite) dominates over the nitrite ion. This limits the availability of nitrite for the organisms that need it, and high levels of nitrous acid are actually toxic to the microbes themselves, causing structural damage to their cells.15PubMed Central. Nitrification in acidic and alkaline environments – Section: Nitrite acquisition and oxidation
For gardeners and farmers, this matters because the effectiveness of nitrogen fertilizers depends partly on soil pH and the activity of these microbial communities. In very acidic soils, the nitrification process slows down, nitrite can accumulate, and the nitrogen you apply may not convert efficiently into the plant-available nitrate form. Liming acidic soils raises the pH and helps keep these microbial pathways running smoothly, which is ultimately about managing the downstream chemistry that nitric acid set in motion when it was used to produce the fertilizer in the first place.
Rocket Propellants and Aerospace
Nitric acid, particularly in concentrated forms like “red fuming nitric acid” and “white fuming nitric acid,” has a long history as a liquid rocket oxidizer. Several early and mid-twentieth-century rocket and missile programs used nitric acid because it is storable at room temperature, unlike cryogenic oxidizers such as liquid oxygen. The acid reacts vigorously with fuels like aniline, furfuryl alcohol, and kerosene derivatives, and some fuel combinations are hypergolic, meaning they ignite on contact without needing a separate ignition source.
While nitric acid has largely been replaced by other oxidizers in modern large-scale launch vehicles, it still sees use in certain military missiles and sounding rockets, and it remains a subject of study in propulsion research. Its corrosiveness and toxicity are significant drawbacks, requiring specialized tanks and handling procedures, but its storability and reliable performance keep it relevant in niches where cryogenic fuels are impractical.
Household and Consumer Products
You will not typically find a bottle labeled “nitric acid” on a store shelf, but the chemical shows up in diluted or derivative forms in several consumer-accessible products. Some heavy-duty drain cleaners contain small amounts of nitric acid, though sulfuric acid is more common. Certain metal-cleaning solutions, especially those marketed toward hobbyists working with copper, brass, or stainless steel, may include dilute nitric acid. Jewelry-cleaning kits occasionally contain acid testing solutions that rely on nitric acid to assess gold purity.
Ammonium nitrate, the fertilizer-grade product of nitric acid and ammonia, appears in instant cold packs. When the inner pouch is broken, ammonium nitrate dissolves in water and absorbs heat, producing the cooling effect. And as mentioned earlier, nitrocellulose, born from the reaction of cellulose with nitric acid, is a common ingredient in nail lacquers and fast-drying coatings. So while pure nitric acid itself is not something most people handle directly, its chemical fingerprint is woven into a surprising number of everyday items.
Other Planets and Moons
Nitric acid chemistry is not limited to Earth. Researchers have searched for nitric oxide, a precursor to nitric acid, in the atmospheres of both Venus and Mars. Venus, with its thick, carbon dioxide-dominated atmosphere and sulfuric acid clouds, presents conditions where nitrogen-oxygen chemistry could produce trace amounts of nitric acid, though the dominant acids in its clouds are sulfuric. Mars, with its thin atmosphere and surface chemistry influenced by ultraviolet radiation, has nitrogen oxide chemistry of its own, though at far lower concentrations.16Icarus. A sensitive search for nitric oxide in the lower atmospheres of Venus and Mars: Detection on Venus and upper limit for Mars
These planetary studies are not just academic curiosity. Understanding nitrogen-oxygen chemistry on other worlds helps scientists model atmospheric evolution and assess whether certain environments could support the kinds of chemical cycles that, on Earth, underpin biology. Nitric acid sits at the intersection of nitrogen, oxygen, and water chemistry, three of the ingredients that make a planet chemically interesting.