oxalic acid
Enable an agent to recognise oxalic acid, assess the form and condition of a particular sample, and determine which handling, analytical or application decisions its evidence supports.
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 recognise oxalic acid, assess the form and condition of a particular sample, and determine which handling, analytical or application decisions its evidence supports.
Oxalic acid is the simplest dicarboxylic acid, with formula H2C2O4 and structure HOOC-COOH, occurring in anhydrous and hydrated forms and forming hydrogen oxalate and oxalate salts on deprotonation.
It can be Resolve a label or supplier record to the correct oxalic-acid form and flag conflicting identity evidence.; Convert weighed material to oxalic-acid amount using verified hydration state and assay.; Assess whether a sample meets the purity and impurity requirements of a proposed use.; Evaluate dissolution, acid-base behaviour and possible metal-oxalate formation under specified conditions.; Compare a proposed application with evidence for substrate compatibility and performance.; Identify handling, storage and waste constraints from applicable safety records..
Distinguishing features
Identity evidence must support the two directly connected carboxyl groups of HOOC-COOH, distinguishing oxalic acid from other organic acids.
A sample identified as oxalic acid must be distinguished from an oxalate salt by its composition and any counterions; acidity alone is insufficient.
Anhydrous material and the dihydrate must be distinguished by water-content or solid-form evidence because equal weighed masses do not contain equal amounts of oxalic acid.
An aqueous sample requires analytical concentration and solution conditions; pH alone does not establish oxalic-acid identity or concentration.
A product containing oxalic acid must retain its mixture identity rather than inherit the identity or purity of the isolated substance.
Scope
+ Chemical identity and the distinction between anhydrous oxalic acid, hydrated material and dissolved acid
+ Sample purity, grade, water content and application-relevant impurities
+ Physical state and measured properties under stated conditions
+ Acid dissociation, oxalate speciation, metal binding and precipitation behaviour
+ Evidence supporting intended uses, exposure controls, storage and disposal
- Oxalate salts and esters as independently identified substances
- Complete formulations of cleaning products or other mixtures containing oxalic acid
- Manufacturing plants and synthesis processes
- Whole-organism oxalate metabolism, disease diagnosis and clinical treatment
- Application equipment and complete operating procedures
Characteristics
- Substance and form identity
- Anhydrous oxalic acid; oxalic acid dihydrate; other or unresolved form Determines which identity records, mass conversions and property references apply.
- Regulatory and database identifiers
- Verified CAS, PubChem CID and EC records, with their covered chemical form Prevents records for different forms or related oxalates from being treated as interchangeable.
- Oxalic-acid assay
- Mass fraction or %, with method and as-received, dry or anhydrous-equivalent basis Makes purity claims and weighed quantities interpretable.
- Water content
- % by mass, with method and distinction between hydration water and other moisture where established Supports form identification and corrections to analytical or application quantities.
- Grade and impurity profile
- Declared grade, applicable specification and measured impurity limits A grade label alone does not establish suitability for a sensitive use.
- Physical condition
- Solid or solution; temperature; visible contamination; caking or other observed changes Records the actual material being assessed rather than assuming reference conditions.
- Solution concentration
- mol/L, g/L or mass %, with solvent, temperature and acid-equivalent basis Supports reproducible comparisons and avoids confusing hydrate mass with dissolved acid content.
- Acid-oxalate speciation conditions
- pH, temperature, ionic strength and relevant dissolved-ion concentrations These conditions affect protonation, metal binding and precipitation.
- Solubility and thermal behaviour
- Solubility in stated units and solvent; thermal events in °C with method, pressure and event assignment Dissolution, dehydration, melting and decomposition must not be collapsed into an unsupported property value.
- Applicable hazard and exposure record
- Current form- or mixture-specific safety data, jurisdiction, classification and exposure-limit basis Connects handling decisions to the material and rules that actually apply.
Also called
Where this came from
wikidata · CC0 1.0
Also registered as vr.tr.oxalic-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.
Chemical identity and boundaries Establishes what counts as oxalic acid and which chemical form a record describes.
Confusion among the free acid, its hydrate, oxalate salts and formulated products propagates into quantity and safety errors.
Molecular identity
Connects names and identifiers to the oxalic-acid structure.
Acid identity evidence
Require evidence that identifies oxalic acid rather than inferring identity from acidity or an oxalate-related name.
- What structural or analytical evidence identifies this material as HOOC-COOH? definition
- Which authoritative identifier records were checked, and what chemical form does each cover? provenance
Hydrate and mixture boundaries
Separates substance identity from hydration state, counterions and product formulation.
Form and boundary resolution
Record the acid's form while preserving separate identities for salts and containing products.
- Does the record describe anhydrous acid, dihydrate, a solution or an unresolved form? definition
- Do counterions or additional ingredients require linking this record to an oxalate-salt or mixture model? boundary
Sample composition and quantity Makes sample-level claims about purity, water and usable acid content explicit.
Oxalic-acid quantities depend on hydration and assay, while impurities can determine whether a nominally correct substance is usable.
Assay and water basis
Defines how measured mass relates to oxalic-acid content.
Acid-equivalent accounting
Keep assay and water-content results on explicit bases before calculating amounts.
- What are the measured assay and water content, and are they reported as received, on a dry basis or as anhydrous acid? measurement
- What verified form and assay corrections are required to convert this sample's mass into moles of oxalic acid? action
Grade and contaminants
Relates lot evidence to application-specific composition requirements.
Lot suitability evidence
Evaluate actual specifications and impurity measurements rather than treating a grade name as sufficient.
- Which certificate, lot and test methods support the claimed grade and impurity profile? provenance
- Which impurities could interfere with the intended analysis, metal treatment or other application, and what acceptance limits apply? action
Physical and solution behaviour Records how oxalic acid behaves as a solid and in a specified solution.
Hydration, thermal changes and acid-oxalate speciation make condition-free property values unreliable for decisions.
Solid form and thermal events
Associates physical observations and thermal measurements with a confirmed form.
Conditioned physical properties
Distinguish measured events and their conditions instead of assuming every reported temperature is a melting or boiling point.
- What form, sample condition and measurement method accompany the reported physical properties? measurement
- Does each observed thermal event represent dehydration, melting, decomposition or an unresolved combination? definition
Dissolution and speciation
Describes dissolved acid content and the conditions governing protonation and metal interactions.
Solution state evidence
Record analytical concentration separately from pH and account for relevant metal ions.
- What solvent, temperature, concentration and pH describe the solution, and is undissolved material present? measurement
- Under these conditions, what evidence supports the expected acid-oxalate species, metal complexes or oxalate precipitates? provenance
Application and compatibility Connects oxalic acid's chemical behaviour and sample quality to a specified purpose.
Acid action, metal interaction and analytical reactivity create different suitability requirements and possible unwanted effects.
Surface and metal interactions
Assesses treatment performance alongside changes to the contacted material.
Substrate-specific suitability
Require application evidence that addresses both the intended effect and substrate compatibility.
- What deposit or surface change is the application intended to achieve, and which oxalic-acid interaction is expected to produce it? definition
- What evidence establishes acceptable substrate alteration, residual oxalate and metal-containing residue under the proposed conditions? action
Analytical and reagent use
Determines whether a sample can support a defined quantitative or reagent function.
Method-specific reagent fitness
Connect hydration, assay and reaction conditions to the requirements of the analytical method.
- Which method specifies the required oxalic-acid form, purity and preparation or standardisation basis? provenance
- What checks establish that water content, impurities and reaction conditions permit the intended quantitative result? action
Exposure, storage and waste Links the actual oxalic-acid material and use conditions to supported handling constraints.
Solid dust, solutions and metal-containing spent material require assessments tied to their composition and exposure circumstances.
Hazard and exposure context
Identifies applicable classification and exposure information for the material being handled.
Applicable safety evidence
Retain the source, date, jurisdiction and material coverage of safety claims.
- Which current safety data and jurisdiction-specific classifications apply to this solid form or solution concentration? provenance
- What exposure routes and airborne forms are credible for the task, and which verified limits and controls apply? action
Storage and spent material
Addresses preservation of sample condition and the changed composition of material after use.
Lifecycle handling constraints
Base storage compatibility and waste decisions on actual composition, including acquired metals and other contaminants.
- Which verified container, segregation and environmental requirements preserve this material's specified condition? action
- After use, what acid, oxalate, metal and other contaminant content determines the applicable waste route? boundary
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 recalled information; no sources were consulted.
- Verify current substance-specific GHS classifications, exposure limits and regulatory obligations before operational use.
- Verify purity, hydration state and measurement conditions before assigning solubility or thermal constants; dehydration and decomposition complicate melting-point reports.
- Which of these check these first hold for the sense of oxalic 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 oxalic acid
- Oxalic acid dihydrate
- Technical-grade oxalic acid
- Analytical-reagent-grade oxalic acid
- Which of these kinds and varieties hold for the sense of oxalic 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 - 144-62-7 - Anhydrous oxalic acid.
- CAS Registry Number - 6153-56-6 - Oxalic acid dihydrate.
- PubChem CID - 971 - Oxalic acid.
- EC number - 205-634-3 - Oxalic acid substance identity.
- IUPAC nomenclature - Ethanedioic acid - Systematic name; oxalic acid is the commonly used name.
- Which of these identifiers and schemes hold for the sense of oxalic 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 chemical hazards.
- European Union REACH Regulation: chemical registration and supply-chain information requirements.
- European Union CLP Regulation: classification, labelling and packaging of substances and mixtures.
- United States OSHA Hazard Communication Standard: workplace chemical labels and safety data sheets.
- Which of these standards and regulation hold for the sense of oxalic 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.
- Rust and iron-stain removal in formulated cleaning products.
- Wood bleaching and removal of iron-related discoloration.
- Reducing reagent in analytical chemistry, including permanganate titrations.
- Preparation of oxalate salts and metal oxalate precursors.
- Active ingredient in some authorized treatments against Varroa mites in honeybee colonies.
- Which of these real-world use hold for the sense of oxalic 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, anhydrous acid - 90.03 - g/mol
- Molar mass, dihydrate - 126.07 - g/mol
- First aqueous acid dissociation constant, pKa1 - Approximately 1.25 near 25 °C; depends on measurement conditions - dimensionless
- Second aqueous acid dissociation constant, pKa2 - Approximately 4.27 near 25 °C; depends on measurement conditions - dimensionless
- Which of these typical measurements hold for the sense of oxalic 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.
- Ingestion can cause serious poisoning, including calcium depletion and kidney injury associated with calcium oxalate formation.
- Eye contact can cause serious injury; skin effects depend on concentration and exposure.
- Airborne dust or mist can irritate the respiratory tract.
- Confusing anhydrous material with the dihydrate produces errors in solutions prepared by mass.
- Heating can cause dehydration or decomposition; decomposition can release carbon monoxide and carbon dioxide.
- Which of these failure modes and hazards hold for the sense of oxalic acid this model covers, and on what evidence? provenance
Regional variation
Recalled without web access and unsourced; every item is a lead to verify.
- Legally required hazard classifications, labels and occupational exposure limits depend on jurisdiction and product composition.
- Authorization of oxalic-acid products for beekeeping, including permitted formulations and application methods, varies by jurisdiction.
- Which of these regional variation hold for the sense of oxalic 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.
- Oxalate - Oxalate is the dianion C2O4²⁻ or a salt containing it; oxalic acid is the parent acid.
- Calcium oxalate - A sparingly soluble calcium salt of oxalic acid, rather than the free acid.
- Oxalic acid dihydrate - Contains two waters of crystallization per acid molecule, giving a different formula mass from anhydrous oxalic acid.
- Oxalic-acid cleaning product - A formulation containing oxalic acid and other ingredients, rather than the substance alone.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of oxalic acid this model covers, and on what evidence? provenance
What the second pass must settle
- Which authoritative CAS, PubChem and EC records apply to anhydrous oxalic acid and its dihydrate, and how should those form-specific records link to this single registry entry?
- Which sources provide reliable form-specific solubility and thermal data, including whether reported melting or boiling values instead describe dehydration or decomposition?
- Which acid-dissociation and metal-oxalate equilibrium data are adequate for the intended temperature, solvent and ionic-strength ranges?
- Which current hazard classifications and occupational exposure limits apply in the jurisdictions of use, and how do they distinguish solid material from solutions?
- Which grade specifications and application studies establish acceptable impurities, substrate effects and residual oxalate for the uses this model should support?