hydrofluoric acid
Enable an AI agent to recognise hydrofluoric acid, assess a particular solution's composition and condition, and determine which uses, handling decisions and escalations require verified 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 AI agent to recognise hydrofluoric acid, assess a particular solution's composition and condition, and determine which uses, handling decisions and escalations require verified evidence.
Hydrofluoric acid is an aqueous solution of hydrogen fluoride (HF), a weak acid in dilute water whose fluoride chemistry makes it highly toxic, corrosive, and capable of attacking silica.
It can be Resolve whether a record describes hydrofluoric acid, anhydrous hydrogen fluoride or a formulated mixture.; Compare a lot's measured concentration and impurity limits with a specified application requirement.; Select property evidence that matches the solution's concentration and operating conditions.; Screen proposed contact materials against documented compatibility limits.; Determine whether identity, condition and safety evidence are sufficient to release a lot for an already authorised use.; Flag compromised containment, suspected exposure or unresolved composition for specialist handling..
Distinguishing features
Identify an aqueous HF material from its composition and documentation; the formula HF alone does not distinguish hydrofluoric acid from anhydrous hydrogen fluoride.
Distinguish HF content from total fluoride: a fluoride-containing solution is not automatically hydrofluoric acid.
Distinguish hydrofluoric acid from fluorosilicic acid and mixed-acid formulations through constituent identity rather than an informal product name.
Do not interpret its classification as a weak acid as evidence of low hazard; acid dissociation, corrosivity and fluoride-related toxicity are separate assessments.
Treat concentration and grade as material-defining attributes when deciding whether two lots are interchangeable.
Scope
+ Aqueous hydrogen fluoride identity and its distinction from anhydrous hydrogen fluoride and other fluoride-containing solutions
+ HF concentration, analytical basis, impurities and application-specific grade
+ Solution properties and phase behaviour at stated composition, temperature and pressure
+ Chemical compatibility, corrosivity and fluoride-related exposure hazards
+ Lot-specific provenance, containment condition and applicable classification
- Anhydrous hydrogen fluoride as a separately characterised material
- Fluoride salts and fluorosilicic acid as distinct substances
- Formulated cleaning or etching products beyond their hydrofluoric-acid constituent
- Industrial manufacturing and etching processes as complete operational models
- Clinical diagnosis and treatment protocols for exposed people
- Facility-wide ventilation, emergency-response and waste-treatment system design
Characteristics
- Material identity and identifier scope
- Preferred name; verified CAS number, PubChem CID and EC number; whether each identifier denotes HF, an aqueous solution or a formulation Prevents an identifier for the molecular substance from being mistaken for a complete description of a solution.
- HF concentration
- Mass fraction as % w/w; other concentration units only with their basis and conversion conditions Concentration affects properties, hazards, compatibility and suitability for use.
- Assay meaning and confidence
- Nominal or measured; analytical method; HF assay, total acidity or total fluoride; uncertainty and analysis date These analytical quantities are not interchangeable in contaminated or mixed solutions.
- Grade and impurity profile
- Supplier grade specification; impurity identities and limits in mg/kg or µg/kg A grade label alone does not establish suitability for contamination-sensitive applications.
- Temperature, pressure and physical state
- Temperature in °C; pressure in kPa absolute; liquid, frozen or multiphase condition The observed state and applicable property data depend on environmental conditions and composition.
- Composition-dependent physical properties
- Density in kg/m³; freezing and boiling behaviour in °C; vapour pressure in kPa, each with concentration and measurement conditions Pure-HF constants cannot be assumed to describe an aqueous solution.
- Contact-material compatibility
- Contact material and component; supported concentration, temperature and duration; compatible, incompatible or unresolved Container, seal and equipment suitability must be demonstrated for the actual service conditions.
- Applicable hazard classification
- Jurisdiction, classification framework, concentration basis, hazard categories and dated supporting document The solution's classification must be established from applicable evidence rather than copied from an unspecified HF record.
- Airborne exposure criteria
- ppm or mg/m³; measured species; averaging period or ceiling; jurisdiction and effective date Exposure measurements can only be compared with limits that match the species and time basis.
- Lot and containment condition
- Lot identifier; sealed, opened, compromised or quarantined; inspection and review dates A valid chemical identity does not establish that a particular container remains fit for use.
Where this came from
wikidata · CC0 1.0
Also registered as vr.tr.hydrofluoric-acid
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 19 findings · 31 questions.
Aqueous HF identity Establish what the material is and how its identifiers relate to its actual composition.
Hydrofluoric acid records can conflate aqueous solutions, anhydrous HF and fluoride-containing formulations.
Substance and solution boundary
Separate the aqueous material from adjacent chemical identities.
Water and HF identity
Record evidence that the material is aqueous HF and identify additional intentional constituents.
- What compositional evidence establishes that this material is aqueous hydrogen fluoride? definition
- Do additional constituents make this a formulated product or mixed acid requiring a neighbouring model? boundary
Identifier and lot traceability
Connect chemical identifiers to supplier documentation and the particular lot.
Identifier denotation
Preserve what each identifier actually denotes instead of treating all database records as equivalent.
- Which verified CAS, PubChem and EC records apply, and does each describe HF generally or this aqueous material specifically? provenance
- Which supplier record, safety data sheet revision and certificate of analysis identify this lot? provenance
Concentration and grade Characterise HF content and impurities sufficiently to judge material equivalence and application suitability.
Solutions sharing the name hydrofluoric acid can differ materially in concentration, contamination and allowable use.
Concentration evidence
Make the concentration basis, assay meaning and uncertainty explicit.
HF assay basis
Distinguish measured HF concentration from nominal concentration, total acidity and total fluoride.
- What is the HF concentration, in which units and on what mass or volume basis? measurement
- What analytical method supports that value, and could other acids or fluoride species affect its interpretation? measurement
Purity and use qualification
Relate a documented impurity profile to the intended use.
Grade supported by limits
Represent grade through verifiable acceptance limits rather than a commercial label alone.
- Which limits apply to metals, silicon-containing impurities, other acids and particles, and which were measured for this lot? measurement
- Does this evidence satisfy the intended application's specification, or is further qualification required? action
Solution state and behaviour Connect physical and chemical behaviour to the actual aqueous composition and conditions.
An isolated molecular formula or a single reference constant cannot describe all hydrofluoric acid solutions.
Phase and volatility
Capture concentration-dependent physical properties and their limits of applicability.
Condition-matched properties
Require the composition, temperature and pressure basis for density, phase-transition and vapour data.
- What density, freezing and boiling data apply to this HF concentration at the stated pressure? measurement
- What evidence describes vapour pressure and vapour composition over the relevant temperature range? measurement
Acidity and fluoride speciation
Separate acid behaviour from analytical fluoride content and practical hazard.
Acidity is not a hazard ranking
Prevent pH or weak-acid terminology from substituting for composition and hazard assessment.
- Which acidity or speciation description is supported for this concentration, and what assumptions limit it? definition
- If pH is reported, is the method suitable for this matrix, and what decisions can that result actually support? measurement
Contact and containment Assess material compatibility and the condition of the barriers containing the acid.
Hydrofluoric acid requires specific compatibility evidence, including for glass, metals, polymers and seals.
Chemical contact compatibility
Evaluate each wetted component under its actual service conditions.
Component-specific compatibility
Record documented compatibility limits and reaction hazards for proposed contact materials.
- What evidence supports each container, seal, transfer component and sensor material at this concentration and temperature? provenance
- Could contact with glass, silicate-bearing material or a particular metal cause attack, contamination or hazardous gas generation? boundary
Containment condition and change
Track whether storage and handling history have invalidated the material's assessed condition.
Lot condition review
Connect container integrity, opening history and possible contamination with release or quarantine decisions.
- What inspection and storage records establish container integrity and the absence of suspected contamination or concentration change? provenance
- Which observed changes require quarantine, reassay or specialist inspection before further use? action
Exposure and authorised disposition Link solution-specific hazards to applicable controls, escalation and disposition requirements.
Hydrofluoric acid's corrosive and systemic fluoride hazards require assessment beyond an ordinary acid label.
Exposure hazard evidence
Record supported exposure routes, classifications and monitoring criteria.
Solution-specific hazard assessment
Keep corrosive injury and systemic fluoride toxicity visible without treating symptom severity as a reliable exposure measure.
- Which current hazard classifications apply to this concentration and jurisdiction, and what documents support them? provenance
- Which airborne HF or fluoride limits apply, with what units, sampling basis and averaging periods? measurement
- Which approved emergency procedure must be invoked for suspected exposure, including when immediate symptoms are absent? action
Use, transfer and waste status
Determine whether the identified material may enter a proposed authorised activity or disposition route.
Evidence for disposition
Connect material composition and condition to documented use, transport and waste requirements.
- What verified composition and classification determine the applicable transport description and packaging requirements? boundary
- Do the receiving operation and its approved controls explicitly cover this concentration, grade and quantity? action
- If the acid is spent or contaminated, which constituents and applicable waste rules determine its authorised disposition? 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.
- Melting point, boiling point, density, and vapour pressure require a specified HF concentration; anhydrous HF constants should not be assigned to aqueous hydrofluoric acid.
- Exact hazard categories, transport identifiers, and exposure limits should be checked for the concentration and jurisdiction; weak-acid behaviour does not imply low hazard.
- Which of these check these first hold for the sense of hydrofluoric 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.
- Dilute aqueous hydrofluoric acid
- Concentrated aqueous hydrofluoric acid
- Technical-grade hydrofluoric acid
- Reagent-grade hydrofluoric acid
- Electronic-grade hydrofluoric acid
- Which of these kinds and varieties hold for the sense of hydrofluoric 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.
- CAS Registry Number - 7664-39-3 - Identifies hydrogen fluoride; aqueous products also require a concentration specification.
- EC number - 231-634-8 - Substance identifier for hydrogen fluoride.
- Chemical formula - HF(aq) - Denotes hydrogen fluoride dissolved in water; it does not specify concentration.
- Which of these identifiers and schemes hold for the sense of hydrofluoric 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 provides the hazard communication framework; classification of solutions depends on composition and concentration.
- European Union REACH and CLP regulations govern relevant chemical registration, classification, labelling, and packaging obligations.
- United States OSHA Hazard Communication Standard governs workplace hazard communication.
- United Nations Recommendations on the Transport of Dangerous Goods distinguish hydrofluoric acid transport entries by concentration.
- Which of these standards and regulation hold for the sense of hydrofluoric 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.
- Etching and frosting glass through reaction with silica.
- Removing silicon dioxide in semiconductor manufacturing.
- Pickling and cleaning metals, including use in mixed-acid treatments.
- Laboratory dissolution of silicate materials.
- Which of these real-world use hold for the sense of hydrofluoric acid this model covers, and on what evidence? provenance
Typical measurements
Recalled without web access and unsourced; every item is a lead to verify.
- HF mass fraction in commonly supplied concentrated aqueous reagents - Approximately 40-50; other commercial concentrations exist - % by mass
- Acid dissociation constant expressed as pKa - Approximately 3.2 in dilute aqueous solution near 25 °C - dimensionless
- Which of these typical measurements hold for the sense of hydrofluoric 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.
- Skin contact can cause deep tissue injury and systemic fluoride poisoning; pain may be delayed, particularly with dilute solutions.
- Fluoride can disrupt calcium and magnesium balance, potentially causing life-threatening cardiac effects.
- Inhalation of vapour or mist can cause severe respiratory injury.
- Eye exposure can cause severe damage and loss of vision.
- Attack on glass and other incompatible materials can cause containment failure; reactions with some metals can release flammable hydrogen.
- Which of these failure modes and hazards hold for the sense of hydrofluoric 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, occupational exposure limits, and workplace requirements differ between jurisdictions.
- Transport classification and packaging requirements depend on solution concentration and the applicable transport rules.
- Which of these regional variation hold for the sense of hydrofluoric 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.
- Hydrogen fluoride - Hydrogen fluoride names the compound HF in any relevant state; hydrofluoric acid specifically denotes its aqueous solution.
- Anhydrous hydrogen fluoride - Anhydrous hydrogen fluoride contains little water and is distinct from an aqueous acid solution, although commercial terminology sometimes blurs the distinction.
- Hydrochloric acid - Hydrochloric acid contains dissolved hydrogen chloride rather than hydrogen fluoride and lacks HF's characteristic fluoride-driven attack on silica.
- Buffered oxide etch - Buffered oxide etch is a formulated mixture, commonly containing hydrofluoric acid and ammonium fluoride, rather than hydrofluoric acid alone.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of hydrofluoric acid this model covers, and on what evidence? provenance
What the second pass must settle
- Does the registry intend hydrofluoric acid strictly as aqueous HF, and does an existing Vercy model already own this concept or its anhydrous neighbour?
- Which authoritative CAS, PubChem and EC records best represent the aqueous-material scope without conflating it with anhydrous HF or commercial formulations?
- Which validated sources provide concentration-dependent density, freezing, boiling and vapour-composition data across the intended operating range?
- Which grade specifications, impurity limits and component-compatibility evidence are required for the actual applications this model must support?
- Which jurisdictions and concentration ranges must be covered by current hazard classifications, exposure limits, transport requirements and waste rules?