salicylic acid
Enable an AI agent to identify salicylic acid, assess its amount and material condition, and determine whether a proposed handling, analytical or formulation operation is supported by 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.
Researched by: Codex + Grok
Purpose and description
Enable an AI agent to identify salicylic acid, assess its amount and material condition, and determine whether a proposed handling, analytical or formulation operation is supported by evidence.
Salicylic acid is 2-hydroxybenzoic acid (C7H6O3), an ortho-phenolic carboxylic acid that functions as a plant defense hormone and is manufactured as a crystalline keratolytic and as the industrial precursor of acetylsalicylic acid and salicylate esters.
It can be Request and interpret identity testing against a salicylic acid reference.; Calculate material quantities from assay and a declared acid-equivalent basis.; Assess a proposed dissolution or dilution against evidence for the specified medium and temperature.; Qualify a batch against the salicylic acid requirements of a linked formulation or analytical procedure.; Record neutralization or derivatization and link resulting substances to their own identities.; Quarantine, retest or release material for a named operation using condition history and applicable specifications..
Distinguishing features
Require structural evidence for adjacent hydroxyl and carboxyl substituents on a benzene ring; molecular formula alone cannot distinguish the hydroxybenzoic acid positional isomers. [ChEBI salicylic acid](https://www.ebi.ac.uk/chebi/CHEBI:16914)
Check the neutral identity against C7H6O3 and InChIKey YGSDEFSMJLZEOE-UHFFFAOYSA-N; treat an identifier match as a reference check, not proof of sample composition. [ChEBI salicylic acid](https://www.ebi.ac.uk/chebi/CHEBI:16914)
Require an identity method capable of separating salicylic acid from acetylsalicylic acid, whose phenolic oxygen is acetylated and whose formula is C9H8O4. [ChEBI acetylsalicylic acid](https://www.ebi.ac.uk/chebi/CHEBI:15365)
Distinguish neutral salicylic acid from its conjugate base, salicylate; record sample preparation and reporting basis before interpreting a result labelled salicylate as free acid. [ChEBI salicylic acid](https://www.ebi.ac.uk/chebi/CHEBI:16914)
Scope
+ Evidence identifying salicylic acid and excluding related compounds.
+ Batch assay, impurities, grade and traceability.
+ Salicylic acid concentration, acid-base speciation and dissolved or particulate state in a specified medium.
+ Storage history, condition changes and retest decisions.
+ Material requirements and constraints for sampling, dissolution, formulation and chemical conversion.
- Independent identities and specifications of salicylate salts, esters and acetylsalicylic acid.
- Complete cosmetic or medicinal formulations and their finished-product performance.
- Patient diagnosis, prescribing and individual treatment decisions.
- Plant signalling networks, biosynthetic pathways and organism-level responses.
- Manufacturing equipment, plant operation and complete reaction-process models.
Characteristics
- Identity evidence
- unverified | supported | conflicting, with method and reference Controls whether the sample may be treated as salicylic acid.
- Salicylic acid assay
- % mass fraction, with as-received or dry basis and uncertainty Supports quantity calculations without equating nominal purity with measured content.
- Concentration and analyte basis
- mol/L, g/L or explicit mass fraction; neutral acid, unconjugated total or total after conversion Prevents chemically different analytical totals from being used interchangeably.
- Medium conditions
- temperature in °C; pH where meaningful; solvent composition with explicit fractions Provides the conditions needed to interpret dissolution and speciation.
- Dissolved fraction
- % of measured salicylic acid equivalents, with separation method and temperature Distinguishes material available in solution from suspended or precipitated material.
- Related substances
- identified analyte concentrations in mg/kg or %, plus detection limits and unresolved peaks Allows suitability decisions to consider contaminants and conversion products.
- Water and residual solvents
- water in % mass fraction; named solvents in mg/kg Qualifies assay basis and compatibility with the intended operation.
- Solid condition
- observed appearance, agglomeration, particle condition and solid-form evidence Supports investigation of changed handling or dissolution behaviour.
- Claimed material grade
- technical | reagent | pharmacopoeial | reference material | other | unspecified, with named specification Makes grade claims testable against the requirements of the intended use.
- Batch and host linkage
- supplier lot, certificate, sample, container and containing formulation or biological specimen Attaches evidence to the actual material and prevents constituent properties from being assigned to an entire mixture.
- Operation suitability
- supported | conditional | unsupported | undetermined, for a named operation Avoids interpreting a successful identity test as unrestricted permission to use the material.
Also called
Where this came from
wikidata · CC0 1.0
Also registered as vr.tr.salicylic-acid
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 18 findings · 28 questions.
Salicylic acid identity Establish what chemical entity and material occurrence the record represents.
Related salicylates and hydroxybenzoic acid isomers must not inherit the identity or suitability of salicylic acid.
Structural recognition
Connect the registered identity to evidence from the sample.
Ortho-hydroxybenzoic identity
Record evidence sufficient to distinguish salicylic acid from positional isomers and acetylated material.
- Which structural reference defines the salicylic acid identity used by this record? definition
- Which sample measurements distinguish that identity from plausible isomers and acetylsalicylic acid? measurement
Substance and constituent boundaries
Separate the chemical identity from its host and related chemical forms.
Acid, salt and host attribution
Specify whether the record concerns bulk acid, an acid constituent or a result reported as acid equivalents.
- Does the evidence describe neutral acid, a salicylate salt or a measurement expressed as salicylic acid equivalents? boundary
- Which batch, mixture or specimen contains the measured constituent, and which neighbouring model owns that host? provenance
Assay and material quality Determine how much salicylic acid is present and what qualifies the material for a particular use.
Identity alone does not establish usable quantity, impurity acceptability or compliance with a grade claim.
Quantitative basis
Make assay and concentration results comparable.
Selective salicylic acid assay
Record method selectivity, preparation effects and the basis of the reported quantity.
- Does the assay selectively measure salicylic acid or also respond to other acidic or salicylate-containing substances? measurement
- Is the result reported as received, on a dry basis or after a preparation step that converts other substances into the measured analyte? measurement
Impurities and grade
Relate batch evidence to explicit acceptance requirements.
Batch quality evidence
Capture relevant impurities, water, solvents and the documentary basis of grade claims.
- Which impurity, water and residual-solvent results are available for this lot, with what detection limits? measurement
- Which named specification and edition support the claimed grade, and does its certificate apply to this lot? provenance
Speciation and phase behaviour Describe the acid's chemical form and distribution between dissolved and solid material.
Nominal concentration cannot by itself establish neutral-acid concentration or whether the material is fully dissolved.
Acid-base state
Interpret neutral acid and salicylate amounts under recorded medium conditions.
Conditioned speciation
Separate measured species amounts from estimates based on equilibrium assumptions.
- What solvent composition, temperature and applicable pH measurement accompany the result? measurement
- What evidence supports the neutral-acid fraction, and are any equilibrium constants valid for this medium? measurement
Dissolution and precipitation
Record whether salicylic acid remains dissolved through the proposed operation.
Dissolved material availability
Assess dissolved amount, residual solid and evidence for changes during dilution or storage.
- How much salicylic acid is dissolved versus particulate at the stated temperature, and how was that separation measured? measurement
- What evidence supports maintaining the required dissolved amount after the proposed cooling, dilution or pH adjustment? action
Condition and chemical fate Track changes in salicylic acid material and transitions into related substances.
A historical certificate cannot establish present condition, and chemical conversion must not silently preserve the original identity.
Storage and retest
Connect exposure history and observations to continued batch suitability.
Current batch condition
Record changes requiring investigation without assigning an unverified degradation mechanism.
- What container, temperature, moisture and light-exposure history is known since the last accepted assay? provenance
- Do changes in appearance, solid condition, assay or impurity profile require retesting under the applicable specification? action
Conversion boundaries
Maintain chemical identity and quantity accounting across transformations.
Salicylic acid consumption or formation
Link operations that consume or produce salicylic acid to measured inputs, outputs and neighbouring substances.
- Does the operation change only phase, alter protonation or create a covalently different substance requiring a linked identity? boundary
- What measurements establish remaining or newly formed salicylic acid rather than assuming complete conversion? measurement
Use and handling decisions Connect salicylic acid evidence to a specific proposed operation and its governing requirements.
Reagent suitability, formulation suitability and biological application require different evidence even when chemical identity is shared.
Application material fit
Evaluate the constituent requirements supplied by the intended application.
Purpose-specific acceptance
Determine whether the batch meets the assay, impurity and physical-state requirements of a named use.
- Which salicylic acid requirements does the linked analytical, formulation or biological protocol impose? provenance
- Which requirements are satisfied, failed or unverified for this batch and proposed concentration? action
Exposure and operation controls
Attach applicable handling evidence to the actual form and operation.
Supported handling envelope
Record the evidence needed to authorize weighing, transfer, mixing, storage or disposal.
- Which current safety document and compatibility evidence cover this salicylic acid material, including its solvent when present? provenance
- What controls and restrictions apply to the proposed amount, concentration, exposure route and operation? 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.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Pharmaceutical-grade crystalline acid (Ph. Eur./USP assay material for medicines)
- Cosmetic-grade acid sold under INCI name Salicylic Acid for leave-on and rinse-off products
- Technical/industrial grade used as a chemical intermediate
- Reagent/analytical grade for laboratory assay
- Endogenous free acid in plants, as distinct from conjugated salicylic acid glucoside (SAG)
- High-strength keratolytic presentations (wart, corn and callus plasters) versus low-strength acne/seborrhoea presentations
- Which of these kinds and varieties hold for the sense of salicylic acid this model covers, and on what evidence? provenance
Identifiers and schemes
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- CAS Registry Number - 69-72-7 - Parent free acid
- IUPAC name - 2-hydroxybenzoic acid
- EC / EINECS - 200-712-3
- UNII - O414PZ4LPZ
- PubChem CID - 338
- ChEBI - CHEBI:16914
- InChIKey - YGSDEFSMJLZEOE-UHFFFAOYSA-N
- Wikidata - Q193572 - Item for the chemical substance, not for aspirin
- ATC - D01AE12 - Topical salicylic acid as a single agent
- HS (Harmonized System) - 2918.21 - Salicylic acid and its salts
- INCI - Salicylic Acid
- Which of these identifiers and schemes hold for the sense of salicylic acid this model covers, and on what evidence? provenance
Standards and regulation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- United States Pharmacopeia, Salicylic Acid monograph (identity, melting range, assay) - USP
- European Pharmacopoeia, Salicylic acid monograph - EDQM, Council of Europe
- 21 CFR 333.310, acne active ingredients: salicylic acid 0.5-2% - US FDA
- 21 CFR 358.110, wart remover active ingredients: salicylic acid 12-40% - US FDA
- Regulation (EC) No 1223/2009, Annex III restriction and Annex V preservative listing - European Union
- SCCS opinions on salicylic acid (CAS 69-72-7), including restriction in products intended for children under three years - European Commission
- REACH registration of 2-hydroxybenzoic acid - ECHA
- Which of these standards and regulation hold for the sense of salicylic acid this model covers, and on what evidence? provenance
Real-world use
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Over-the-counter acne cleansers, toners and leave-on treatments at about 0.5-2% as a lipid-soluble keratolytic
- Wart, corn and callus plasters and collodion at about 12-40%
- Anti-dandruff and scalp shampoos, and chemical peels in dermatology clinics
- Industrial acetylation to acetylsalicylic acid (aspirin) and esterification to methyl salicylate
- Plant-pathology and crop-science work on systemic acquired resistance, where tissue free SA and SAG are quantified
- Historical food preservative use, now largely displaced by regulation
- Intermediate in dyes, fragrances and some phenolic resin chemistry
- Which of these real-world use hold for the sense of salicylic acid this model covers, and on what evidence? provenance
Typical measurements
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Assay (pharmaceutical grade) - 99.0-100.5 - % w/w
- Melting range - 158-161 - °C
- Aqueous solubility at ~25 °C - 1.8-2.5 - g/L
- Acid dissociation constant (carboxylic) - 2.97-3.0 - pKa
- Molecular mass - 138.12 - g/mol
- Acne/cosmetic leave-on concentration - 0.5-2 - % w/w
- Wart/callus keratolytic concentration - 12-40 - % w/w
- Octanol-water partition coefficient - ~2.3 - log P
- Which of these typical measurements hold for the sense of salicylic acid this model covers, and on what evidence? provenance
Failure modes and hazards
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Chemical burns and excessive desquamation from high-strength or occluded application
- Percutaneous salicylate poisoning (salicylism) after large-area use, especially in children or on damaged skin
- Contact dermatitis and cross-reactivity in people with salicylate/aspirin sensitivity
- Oral toxicity if ingested; rodent oral LD50 on the order of 0.9 g/kg
- Thermal decarboxylation on strong heating, releasing phenol-type fumes
- Combustible crystalline solid with dust-explosion potential when finely divided
- Use on paediatric viral illness is treated with the same clinical caution as other salicylates because of Reye-syndrome association with this chemical class
- Which of these failure modes and hazards hold for the sense of salicylic acid this model covers, and on what evidence? provenance
Regional variation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- United States treats many 0.5-2% acne and 12-40% wart products as OTC drugs under FDA monographs; the EU more often regulates the same molecule as a restricted cosmetic ingredient, with higher strengths falling into medicines law
- EU cosmetic practice caps body-lotion and some face/eye products lower than rinse-off hair products, and generally keeps products for children under three years off the market except certain shampoos
- English-language skincare marketing calls it a BHA, which collides with the food-additive sense of BHA (butylated hydroxyanisole)
- Willow-bark preparations are still sold as herbal products in some markets and are not chemically equivalent to a declared salicylic acid assay
- Which of these regional variation hold for the sense of salicylic acid this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Acetylsalicylic acid (aspirin) - The phenolic OH is acetylated; distinguish by the extra acetyl 1H/13C NMR signals, the ester carbonyl in IR, and CAS 50-78-2 versus 69-72-7
- Methyl salicylate (oil of wintergreen) - Carboxyl group is a methyl ester; wintergreen odour and a distinct GC-MS molecular ion separate it from the free acid
- 4-Hydroxybenzoic acid (and paraben esters) - Para rather than ortho substitution; melting point, 1H NMR coupling pattern, and CAS 99-96-7 separate the isomer
- Salicin / willow-bark extract - A β-glucoside of salicyl alcohol, not free 2-hydroxybenzoic acid; HPLC against a salicylic acid standard shows the glycoside, not the acid, until hydrolysed
- Glycolic or lactic acid (AHAs) - Aliphatic α-hydroxy acids, fully water-soluble and not lipid-soluble BHAs; pKa, log P and the absence of an aromatic UV chromophore separate them
- Benzoyl peroxide - A peroxide oxidant used for acne, not a phenolic acid; peroxide test strips and the absence of a carboxylic acid titration distinguish it
- Benzoic acid - Lacks the ortho-phenolic OH; mixed melting point and 1H NMR (no downfield phenolic proton next to COOH) separate it
- Which of these neighbouring kinds and how to tell them apart hold for the sense of salicylic acid this model covers, and on what evidence? provenance
Sources
- PubChem Compound Summary for CID 338, Salicylic Acid - Identity (CAS, InChIKey, molecular formula), physical constants, toxicity figures, and common identifiers
- 21 CFR Part 333 - Topical antimicrobial drug products for over-the-counter human use - United States OTC acne monograph concentration band for salicylic acid
- 21 CFR Part 358 Subpart B - Wart remover drug products - United States OTC wart-remover monograph concentration band
- Regulation (EC) No 1223/2009 of the European Parliament and of the Council on cosmetic products - European cosmetic restriction and preservative listing of salicylic acid
- SCCS Opinion on salicylic acid (CAS 69-72-7) - European scientific limits and age restrictions used to justify cosmetic annex entries
- Salicylic acid monograph (European Pharmacopoeia; United States Pharmacopeia) - Pharmaceutical identity, melting range, and assay specification for medicinal grade
What the second pass must settle
- Which validated identity and assay methods provide adequate discrimination from hydroxybenzoic acid isomers, acetylsalicylic acid and relevant matrix components?
- Which solubility and acid-base equilibrium data are reliable for the solvents, temperatures and concentrations the model must support?
- Which current grade specifications define acceptable assay, impurities, water and residual solvents for the intended applications?
- Which documented storage excursions or condition changes justify retesting, and what evidence supports the applicable retest interval?
- Which current jurisdiction-specific requirements and exposure assessments govern each proposed formulation or handling use?