Nitric Acid Concentration and Grade Selection Guide

Nitric Acid Concentration and Grade Selection Guide

Nitric acid (HNO₃) is one of the most versatile mineral acids in industrial chemistry, but "nitric acid" is not a single product. The grade you buy, the concentration you specify, and the container it ships in all change how the material behaves in your process, how you must handle it, and how much it costs to move safely across borders. Procurement teams that treat 65% industrial acid, 68% concentrated acid, 70% ACS reagent, and 98% fuming acid as interchangeable often end up with corroded equipment, off-spec product, or rejected shipments.

This guide walks process engineers, buyers, and compliance staff through the practical decisions: which concentration and grade suit fertiliser production, explosives manufacturing, and acid pickling; why aluminium packaging matters for some concentrations and not others; how to check specifications before you pay; and what to weigh when sourcing from China.

Understanding Nitric Acid Concentrations and Grades

Nitric acid is sold as an aqueous solution across a well-known range of concentrations, each with distinct chemistry.

Dilute to Concentrated (up to ~68-70%)

Commercial "concentrated" nitric acid tops out near the water-acid azeotrope at roughly 68% by weight (about 15 mol/L). Below this, the acid behaves primarily as a strong oxidising acid in aqueous solution. The 65-70% band covers most large-volume industrial use. Within this band you will encounter two very different quality tiers:

• **Industrial or technical grade (typically 65-68%):** Manufactured to functional purity for bulk process feedstock. Trace metals, chloride, and sulfate are controlled to process-tolerant limits rather than analytical limits.
• **ACS reagent grade (often specified around 68-70%):** Certified against American Chemical Society purity standards, with tightly bounded assay, residue after ignition, chloride, sulfate, and heavy-metal limits. This grade is meant for analytical, laboratory, and high-purity applications, not for feeding a nitrophosphate reactor.

Paying reagent prices for a bulk industrial duty is a common and expensive mistake. Conversely, using loosely specified technical acid where trace metals matter can contaminate a finished product.

Fuming Nitric Acid (~98% and above)

At roughly 90% and higher you reach fuming nitric acid, and near 98% the material releases nitrogen dioxide (NO₂) fumes that give it a characteristic red-brown colour (red fuming nitric acid) or, when NO₂ is stripped out, a colourless white fuming grade. Fuming acid is a far stronger oxidiser and nitrating agent than the 68% product. It is used where anhydrous or near-anhydrous conditions and high oxidising power are required, and it demands stricter handling and packaging.

Matching Concentration and Grade to the Application

Fertiliser Production

Nitric acid is a backbone reagent for nitrogen fertilisers. It is used to produce ammonium nitrate by neutralising with ammonia, and to digest phosphate rock in the nitrophosphate route. For these duties, concentration in the 60-68% range is typical, and industrial or technical grade is normally sufficient because downstream reactions tolerate ordinary process-level impurities. What matters most here is consistent assay (so acid-to-ammonia ratios stay controlled), low chloride to protect stainless-steel reactors, and reliable bulk logistics. Reagent-grade purity is rarely justified. Buyers should note that ammonia is the paired feedstock for ammonium nitrate; according to UN Comtrade, China imported ammonia (HS 281410) valued at about USD 197.6 million in 2024, a reminder that fertiliser value chains draw on multiple traded intermediates.

Explosives Manufacturing

Explosives and energetic-materials chemistry relies on nitration, and this is where concentration and water content become decisive. Nitrating aromatics and other substrates typically uses concentrated to fuming nitric acid, frequently in mixed-acid systems with sulfuric acid acting as a dehydrating agent. Fuming grades near 98% supply the high oxidising power and low water content that many nitration reactions require. This is a heavily regulated field: nitric acid is a controlled precursor in many jurisdictions, and buyers must hold the relevant licences, document end use, and comply with explosives-precursor and dual-use controls. No supplier guidance replaces the legal obligation to verify that your intended use and storage are authorised. This guide covers concentration and packaging fundamentals only and does not provide any procedure for manufacturing energetic materials.

Acid Pickling and Metal Finishing

In metal finishing, nitric acid pickles and passivates stainless steel and cleans other alloys, often blended with hydrofluoric acid in stainless pickling baths and used alone for passivation. Pickling baths generally run at moderate, diluted working concentrations made up from 65-68% stock, so a well-specified industrial grade is usually the right buy. The key specification concerns here are chloride content, which can pit stainless surfaces, and consistent assay so bath chemistry stays predictable. For comparison, buyers who also run chloride-based pickling should note that China's 2023 hydrochloric acid imports (HS 280610) were reported at about 6.06 million kilograms in the UN Comtrade dataset, a much smaller traded volume than nitric acid.

Aluminium Packaging: Why Concentration Changes the Container

One of the most misunderstood aspects of nitric acid procurement is packaging metallurgy. The same acid can passivate one metal and rapidly dissolve another depending on concentration.

The Passivation Effect

Highly concentrated nitric acid, including fuming 98% grades, passivates aluminium: the acid forms a thin, adherent oxide layer that protects the underlying metal from further attack. This is why aluminium alloys are a recognised material of construction for storing and transporting concentrated and fuming nitric acid. Aluminium is light, which lowers shipping weight, and it avoids the iron contamination that carbon steel would introduce.

The Concentration Threshold Buyers Must Verify

Passivation is concentration-dependent. As acid becomes more dilute, its behaviour toward aluminium shifts and the protective film can break down, allowing corrosion. In practice, aluminium is best suited to the strong, high-concentration end of the range, while more dilute nitric acid is commonly stored in stainless steel (304L or 316L) or suitable plastics and lined vessels. When a supplier offers both 68% and 98% acid in aluminium containers, treat that as a specification to confirm, not to assume. Ask for the alloy designation, the maximum permitted storage duration, temperature limits, and any documented compatibility data for the exact concentration you are buying. A container that is ideal for 98% fuming acid may not be appropriate for weaker material sitting in it for months. Verifying material compatibility before shipment prevents leaks, contamination, and dangerous container failures in transit.

Specification Checks Before You Pay

A disciplined incoming-specification review protects both product quality and safety. Before releasing payment, request and read the certificate of analysis (CoA) and the safety data sheet (SDS), and check the following:

• **Assay (percent HNO₃):** Confirm the actual concentration matches your purchase, whether 65%, 68%, 70%, or 98%. Assay drift directly affects stoichiometry.
• **Grade designation:** Verify whether the lot is technical, industrial, or ACS reagent, and that it meets the corresponding purity standard.
• **Chloride and sulfate:** Critical for pickling and for stainless-steel process equipment.
• **Iron and heavy metals:** Important for fertiliser purity and for reagent applications.
• **Residue after ignition / non-volatile matter:** Indicates dissolved solids.
• **Colour and appearance:** For fuming grades, colour indicates dissolved NO₂ content and can flag storage or age issues.
• **Packaging and UN specification:** Confirm the container, closure, alloy or liner, net quantity, and that packaging is certified for the dangerous-goods class.

Always reconcile the CoA batch number against the physical label before accepting delivery.

Safe Handling and Compliance

Nitric acid is corrosive and a strong oxidiser, and fuming grades additionally release toxic NO₂ vapour. Handling controls should scale with concentration.

• **Personal protection:** Acid-resistant gloves, face shield and goggles, and appropriate chemical-resistant clothing. For fuming acid, respiratory protection and fume control are essential because NO₂ is a serious inhalation hazard.
• **Ventilation:** Use fume hoods or local exhaust for open handling of concentrated and fuming grades.
• **Segregation:** Store away from organics, reducing agents, bases, and metals that react vigorously with oxidisers. Never mix nitric acid with incompatible chemicals without engineered controls.
• **Spill and first-aid readiness:** Keep suitable neutralising and absorbent materials and eyewash/safety showers accessible.
• **Transport classification:** Nitric acid ships as a Class 8 corrosive (fuming grades carry additional oxidiser and toxicity hazards). Ensure correct UN numbers, packing groups, labelling, and documentation for your mode of transport.

On the regulatory side, nitric acid is subject to precursor controls in many countries. Confirm import licensing, end-use reporting, and any explosives-precursor restrictions before ordering, particularly for high concentrations.

China Sourcing Considerations

China is a major hub for acid manufacturing and trade, and buyers frequently source nitric acid and related mineral acids from Chinese producers. Trade statistics help frame the market context. UN Comtrade data reports China's 2023 nitric acid imports (HS 280800) at roughly 99.3 million kilograms with a trade value near USD 23.6 million, alongside far larger sulfuric acid imports (HS 280700) of about 322 million kilograms and sodium hydroxide imports (HS 281512) around 15.85 million kilograms. These figures describe recorded import flows for the reporting period and should be read as context for scale rather than as a forecast of prices or availability.

When qualifying a Chinese supplier, prioritise documentation and verification over headline price. Working with an established chemical supplier China that can produce consistent CoAs, dangerous-goods-compliant packaging, and clear traceability reduces the risk of off-spec or mislabelled shipments. Confirm that your counterparty operates as a genuine industrial chemicals exporter with export licensing, correct HS classification (280800 for nitric acid), and experience preparing Class 8 corrosive shipments for your destination port. For the product itself, review the technical datasheet and packaging options from a specialist nitric acid supplier and confirm the alloy or liner used for the concentration you intend to store.

Practical due-diligence steps include:

• Requesting a pre-shipment sample and independent third-party analysis for large orders.
• Confirming Incoterms and who bears responsibility for dangerous-goods compliance.
• Checking that packaging matches the concentration (aluminium suitability for fuming versus stainless or lined containers for weaker acid).
• Aligning lead times with your import licensing timeline for controlled concentrations.

Bringing It Together

Choosing nitric acid well comes down to three linked decisions. First, pick the concentration your chemistry actually needs: 65-68% industrial grade for fertiliser digestion and pickling stock, ACS reagent near 70% only where analytical purity is required, and 98% fuming acid where high oxidising power and low water content are essential. Second, match packaging to concentration, verifying aluminium compatibility for strong acid and choosing stainless or lined vessels for more dilute material. Third, back every purchase with a specification review, dangerous-goods compliance, precursor licensing, and supplier due diligence. Get those three right and nitric acid becomes a predictable, well-controlled input rather than a source of corrosion, contamination, or compliance risk.

Sources

• UN Comtrade public trade statistics — Nitric acid (HS 280800), China imports 2023
• UN Comtrade public trade statistics — Sulfuric acid (HS 280700), China imports 2023
• UN Comtrade public trade statistics — Hydrochloric acid (HS 280610), China imports 2023
• UN Comtrade public trade statistics — Sodium hydroxide (HS 281512), China imports 2023
• UN Comtrade public trade statistics — Ammonia (HS 281410), China imports 2024