nitric acid
Enable an agent to identify nitric acid, assess the condition and suitability of a particular material, and determine which handling or use decisions require further evidence.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
recalled by Codex without web access - no source was read
Researched by: Codex
Purpose and description
Enable an agent to identify nitric acid, assess the condition and suitability of a particular material, and determine which handling or use decisions require further evidence.
Nitric acid (HNO₃) is a nitrogen oxoacid that is strongly acidic in aqueous solution and acts as a corrosive oxidizing reagent, with behavior dependent on concentration, temperature and dissolved nitrogen oxides.
It can be Match a label, safety data sheet and batch certificate to the nitric acid identity and actual material composition.; Compare concentration and impurity evidence against the requirements of a declared use.; Select physical-property references that match the sample's composition and conditions.; Flag unexplained changes in appearance or composition for qualified assessment.; Check proposed containment and contact materials against documented compatibility conditions.; Identify missing hazard, exposure or jurisdictional evidence before authorizing a proposed activity..
Distinguishing features
The chemical identity is HNO3; HNO2 identifies nitrous acid, while a nitrate salt requires a counterion and is not itself nitric acid.
Low pH alone cannot identify nitric acid; identification must distinguish it from other acids and establish the relevant chemical composition.
A nitric acid solution requires a stated HNO3 concentration and reporting basis; the name alone does not distinguish dilute solution, concentrated solution and anhydrous material.
Fuming designations require composition evidence, including dissolved nitrogen oxides where relevant; visible fumes or colour alone do not establish a grade.
A formulation containing another deliberately added acid belongs to a mixture model, with nitric acid represented as a constituent.
Scope
+ Nitric acid identity and distinctions from nitrous acid, nitrate salts and mixed-acid formulations
+ Anhydrous and aqueous forms, with explicit concentration bases and dissolved nitrogen oxide content
+ Purity, commercial grade, trace contaminants and evidence of fitness for an intended use
+ Physical properties and material condition at stated temperature, pressure and composition
+ Composition-dependent hazards, compatibility and jurisdiction-specific identity records
- Industrial processes and equipment that manufacture nitric acid
- Finished products and mixed-acid formulations containing nitric acid
- Nitrate salts and nitrous acid as independently registered substances
- Facility ventilation, storage installations and transport equipment
- Medical diagnosis and treatment following exposure
- Detailed procedures for chemical synthesis or reactive processing
Characteristics
- Chemical and registry identity
- HNO3; vr.tr.nitric-acid; source-verified CAS, PubChem and EC identifiers Connects material records to the correct substance and prevents confusion with related nitrogen compounds.
- HNO3 concentration
- Mass fraction or mass percent preferred; other bases explicitly named, with temperature where relevant Concentration affects physical properties, suitability, compatibility and hazard interpretation.
- Water content
- Mass percent, with analytical method and uncertainty Distinguishes aqueous and nominally anhydrous material and helps check composition claims.
- Dissolved nitrogen oxide content
- Reported species or analytical equivalent, concentration basis and method Helps interpret fuming grade, colour, composition changes and headspace concerns.
- Grade and impurity specification
- Supplier grade, governing specification and batch certificate; impurity limits in mg/kg or µg/kg A high acid assay does not by itself establish suitability for contamination-sensitive work.
- Physical state and appearance
- Phase, colour, clarity, visible solids and observed fuming, with observation conditions Supports condition assessment without treating appearance as definitive identification.
- Temperature and pressure
- °C or K; kPa absolute Makes phase, density and volatility observations interpretable.
- Density and phase-transition properties
- Density in kg/m³; melting or freezing and boiling temperatures in °C, each tied to composition and applicable conditions Prevents pure-substance constants from being applied indiscriminately to aqueous solutions.
- Hazard and exposure-limit applicability
- Material linked to dated classification and exposure-limit sources, jurisdiction, concentration range and averaging period Allows an agent to distinguish applicable requirements from generic substance-level statements.
- Contact-material compatibility
- Material pair, concentration, temperature, exposure duration and supporting compatibility evidence Compatibility cannot be inferred reliably from a generic acid-resistant designation.
Also called
Where this came from
wikidata · CC0 1.0
Also registered as vr.tr.nitric-acid
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 19 findings · 29 questions.
Nitric acid identity and boundaries Establishes which chemical entity is represented and where nitric acid records end and neighbouring substance or formulation records begin.
Acidity, nitrate content and commercial names can each produce false matches without a chemical identity boundary.
Chemical identity
Connects the registry entry to independently supported substance identifiers.
HNO3 identity evidence
Record the basis for identifying the material as nitric acid and the authority behind each external identifier.
- Which evidence establishes nitric acid identity rather than merely low pH or the presence of nitrate? definition
- Which authoritative records establish the CAS number, PubChem CID and EC number, and what entity does each record cover? provenance
Substance and mixture boundary
Distinguishes forms of nitric acid from related compounds and separately modelled formulations.
Solution versus formulation
Represent aqueous concentration as a material attribute while linking separately named formulations to their own models.
- Is this material nitric acid, an aqueous nitric acid solution or a formulation containing additional intentional constituents? boundary
- Which constituents are impurities, grade-defining additions or ingredients that require a separate formulation record? boundary
Composition and grade Describes the acid, water, nitrogen oxide and impurity composition that gives a nitric acid sample its practical identity.
The substance name does not specify concentration, fuming designation or analytical suitability.
Acid, water and nitrogen oxides
Makes concentration claims and nitrogen oxide reporting comparable.
Composition basis
Record HNO3 assay, water and dissolved nitrogen oxides with methods and reporting bases.
- What are the measured HNO3 and water contents, and are the results expressed on compatible bases? measurement
- How is dissolved nitrogen oxide content measured and reported, and could it affect the interpretation of the acid assay? measurement
Grade and contaminants
Links commercial grade claims to measurable acceptance criteria.
Grade evidence
Treat grade names as claims requiring specifications and batch evidence.
- Which specification defines this supplier's concentrated, fuming, reagent or trace-analysis grade? provenance
- Which impurity limits and batch results determine whether this material is suitable for its declared use? action
Physical state and condition Relates observable condition and physical-property data to nitric acid composition and environment.
Aqueous composition and nitrogen oxide content make unqualified constants and appearance-based conclusions unreliable.
Conditioned physical properties
Records properties together with the conditions under which they apply.
Property applicability
Require composition and environmental context for density, phase transitions and volatility data.
- Which density, freezing and boiling data apply to this HNO3 concentration at the stated temperature or pressure? measurement
- Does the reference describe pure HNO3, an aqueous mixture or azeotropic behaviour, and which interpretation fits this sample? boundary
Condition over time
Tracks changes without assigning a cause solely from visual observations.
Appearance and composition change
Connect colour, clarity and fuming observations to storage history and analytical evidence.
- How have colour, clarity, fuming observations and measured composition changed since the material was received? measurement
- What evidence distinguishes expected grade appearance from decomposition, contamination or a change in concentration? provenance
Hazards and compatibility Supports assessment of corrosive and oxidizing behaviour, airborne exposure and material contact.
Nitric acid decisions require more than a generic acid label, particularly where concentration and contact materials change the assessment.
Hazard and exposure evidence
Links the actual material to applicable hazard classifications and airborne exposure criteria.
Composition-specific hazards
Record classification and exposure evidence with its concentration range, jurisdiction and date.
- Which corrosivity, oxidizing and other hazard classifications apply to this composition under the relevant jurisdiction? provenance
- Which exposure limits apply to nitric acid vapour or mist, and must nitrogen dioxide be assessed separately for this material or activity? boundary
Contact and containment
Evaluates specific contact materials and incompatible substances using condition-matched evidence.
Compatibility evidence
Require documented compatibility for the proposed concentration, temperature and exposure duration.
- What evidence supports compatibility of the proposed vessel, closure, seal and transfer-contact materials with this nitric acid composition? provenance
- Which potential contacts with organics, reducing agents, bases or metals require segregation or specialist review under the applicable guidance? action
Traceability and use decisions Connects a nitric acid material record to batch evidence, jurisdictional records and a declared intended use.
Substance identity alone cannot establish whether a particular batch meets a use specification or applicable requirements.
Batch and document traceability
Keeps supplier claims and regulatory records attached to the material they actually describe.
Document-to-material match
Check agreement among the container label, supplier product record, safety data sheet and certificate of analysis.
- Do the label, product identifier, batch number, concentration and grade agree across the available documents? provenance
- Which dated transport or jurisdictional records apply to this concentration and formulation rather than to nitric acid generically? boundary
Fitness for declared use
Turns composition, condition and compatibility evidence into a bounded suitability decision.
Use acceptance evidence
Compare the material with explicit requirements and preserve unresolved evidence gaps.
- What concentration, impurity, condition and compatibility requirements must this batch satisfy for the declared use? action
- Which missing, conflicting or outdated evidence prevents a suitability decision and requires qualified review? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Check these first
Recalled without web access and unsourced; every item is a lead to verify.
- This is a recall-based description; no sources were consulted.
- Physical properties require confirmation against acid concentration, water content, dissolved nitrogen oxides, temperature and pressure.
- Verify current regulatory classifications, exposure limits, transport provisions and grade specifications for the actual formulation and jurisdiction.
- Which of these check these first hold for the sense of nitric acid this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- Anhydrous nitric acid
- Dilute aqueous nitric acid
- Concentrated aqueous nitric acid, commonly about 68-70% by mass
- White fuming nitric acid
- Red fuming nitric acid
- High-purity analytical or electronic-grade nitric acid
- Which of these kinds and varieties hold for the sense of nitric acid this model covers, and on what evidence? provenance
Identifiers and schemes
Recalled without web access and unsourced; every item is a lead to verify.
- Chemical formula - HNO3 - Identifies nitric acid; commercial solutions also contain water and may contain dissolved nitrogen oxides.
- CAS Registry Number - 7697-37-2 - Substance identifier for nitric acid.
- PubChem CID - 944 - Compound identifier for nitric acid.
- EC number - 231-714-2 - European chemical inventory identifier.
- UN dangerous goods number - UN 2031; UN 2032 - UN 2031 covers nitric acid other than red fuming; UN 2032 identifies red fuming nitric acid. Transport requirements depend on formulation and concentration.
- Which of these identifiers and schemes hold for the sense of nitric acid this model covers, and on what evidence? provenance
Standards and regulation
Recalled without web access and unsourced; every item is a lead to verify.
- United Nations Globally Harmonized System of Classification and Labelling of Chemicals (GHS): framework for communicating corrosive and oxidizing hazards; implemented through jurisdiction-specific rules.
- European Union REACH Regulation: chemical registration, supply-chain information and related obligations.
- European Union CLP Regulation: classification, labelling and packaging of substances and mixtures.
- United States OSHA Hazard Communication Standard: workplace hazard classification, labels and safety data sheets.
- United Nations Recommendations on the Transport of Dangerous Goods, Model Regulations: transport classification framework.
- Which of these standards and regulation hold for the sense of nitric acid this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Manufacture of ammonium nitrate and other nitrate fertilizers.
- Industrial nitration in the manufacture of chemical intermediates and energetic materials.
- Metal pickling, etching and stainless-steel passivation under controlled conditions.
- Laboratory sample digestion and preparation for elemental analysis.
- Oxidizer in some rocket-propellant systems, particularly fuming formulations.
- Which of these real-world use hold for the sense of nitric acid this model covers, and on what evidence? provenance
Typical measurements
Recalled without web access and unsourced; every item is a lead to verify.
- Molar mass - 63.01 - g/mol
- Melting point of pure nitric acid - approximately -42 - °C
- Boiling point of pure nitric acid at approximately 1 atm - approximately 83, with decomposition possible - °C
- Density of nearly anhydrous nitric acid at approximately 20 °C - approximately 1.51 - g/cm³
- Nitric acid mass fraction in the atmospheric-pressure water azeotrope - approximately 68 - % by mass
- Boiling point of the water azeotrope at approximately 1 atm - approximately 120.5 - °C
- Which of these typical measurements hold for the sense of nitric acid this model covers, and on what evidence? provenance
Failure modes and hazards
Recalled without web access and unsourced; every item is a lead to verify.
- Causes severe chemical burns and serious eye damage; acid mist and fumes can injure the respiratory tract.
- Oxidizing action can intensify fires and cause violent reactions with organic materials, reducing agents and other incompatible substances.
- Reactions with many metals release toxic nitrogen oxides; nitric acid does not follow the simple acid-metal hydrogen-release pattern in all conditions.
- Mixing with water releases substantial heat and can cause localized boiling and corrosive splashing.
- Heat or light can promote decomposition and nitrogen dioxide formation, causing discoloration and potentially pressure buildup in unsuitable containment.
- Which of these failure modes and hazards hold for the sense of nitric acid this model covers, and on what evidence? provenance
Regional variation
Recalled without web access and unsourced; every item is a lead to verify.
- GHS implementation, required label elements and concentration-dependent mixture classifications vary by jurisdiction.
- Occupational exposure limits and their averaging periods differ among authorities.
- Precursor controls, purchasing restrictions and reporting obligations depend on jurisdiction and concentration.
- Which of these regional variation hold for the sense of nitric acid this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Recalled without web access and unsourced; every item is a lead to verify.
- Nitrous acid - HNO2 contains nitrogen in oxidation state +3; nitric acid contains nitrogen in oxidation state +5.
- Nitrate - NO3− is nitric acid's conjugate-base ion; nitrate salts are distinct substances with their own cations and properties.
- Nitrogen dioxide - NO2 is a nitrogen oxide that may dissolve in nitric acid and contribute to red fumes; it is not the acid itself.
- Aqua regia - Aqua regia is a reactive mixture of nitric and hydrochloric acids, rather than a grade of nitric acid alone.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of nitric acid this model covers, and on what evidence? provenance
What the second pass must settle
- Which authoritative identity records should anchor the CAS, PubChem and EC identifiers and their treatment of aqueous forms?
- How do relevant suppliers or standards define concentrated, white fuming and red fuming nitric acid, including dissolved nitrogen oxide limits?
- Which evaluated property sources cover the required concentration range, including freezing behaviour, boiling behaviour and azeotropic composition?
- Which current jurisdiction-specific classifications, exposure limits and transport distinctions apply across the concentrations to be represented?
- Which analytical methods and compatibility references are sufficiently specific to support grade acceptance and condition assessment for the intended uses?