{"schema":"https://ver.cy/schemas/card/1.0.0","id":"vr.tr.methyl-arsonic-acid","code":"thing-q1976186","url":"https://ver.cy/models/thing/q1976186/","name":"methyl arsonic acid","alternateNames":["methylarsonate(2-)","methylarsonate(1-)"],"kind":"thing","status":"published","version":"0.1.0-research.1","language":"en","classifiers":{"family":"Thing Registry","category":"Physical world and living systems","entryKind":"thing","plane":"PHY","domain":["PHY.MAT"],"industry":[],"navPath":"","tags":[],"facets":{}},"whatItIs":"Methylarsonic acid is an organoarsenic compound with formula CH3AsO(OH)2, containing pentavalent arsenic bonded directly to one methyl group and forming methylarsonate salts upon deprotonation.","purpose":"Enable an agent to identify methyl arsonic acid, assess the chemical state and evidential quality of a particular sample, and determine appropriate handling or analytical actions.","scope":{"in":["Free-acid identity, verified identifiers, and synonym ambiguity","Sample purity, grade, water content, and arsenic-containing impurities","Physical state and measured properties under stated conditions","Acid-base speciation and changes in arsenic oxidation state","Species-resolved analytical evidence and concentration reporting","Substance-specific hazards and applicable handling or regulatory constraints"],"out":["Monosodium and disodium methylarsonate as independently identified salt substances","Complete herbicide formulations and their product authorizations","Manufacturing processes and synthesis equipment","Clinical diagnosis or treatment of arsenic exposure","Whole-organism arsenic metabolism models","Site-wide contamination transport and remediation plans"],"boundaries":[]},"distinguishingFeatures":["Verify the free-acid structure CH3AsO(OH)2 and molecular formula CH5AsO3; identity anchors are CAS 124-58-3, PubChem CID 8948, and EC 204-705-6. [PubChem](https://pubchem.ncbi.nlm.nih.gov/compound/Methylarsonic-acid)","Require one methyl group directly bonded to arsenic; distinguish the target from unmethylated inorganic arsenic and dimethylarsinic acid.","Require the pentavalent methylated arsenic identity, conventionally MMA(V), and distinguish it from trivalent methylarsonous acid, MMA(III). [WHO arsenic assessment](https://inchem.org/documents/ehc/ehc224.htm)","Check counterions and preparation records before treating a methylarsonate salt or its solution as a free-acid sample.","Reject total arsenic concentration or the abbreviation MMA alone as sufficient proof of methylarsonic acid identity."],"structure":{"bundles":[{"id":"methylated-arsenic-identity","name":"Methylated arsenic identity","description":"Establishes which chemical entity the registry name denotes and which related entities require separate identities.","layers":[{"id":"free-acid-identity","name":"Free-acid identity","description":"Connects the registered thing to structural and identifier evidence.","findings":[{"id":"structure-controls-name-resolution","name":"Structure controls name resolution","description":"The model should accept name equivalence only when identifiers resolve to the same free-acid structure.","questions":[{"text":"Does the supplied name resolve to CH3AsO(OH)2 and CAS 124-58-3?","id":"structure-controls-name-resolution-q01","kind":"definition"},{"text":"Which authoritative record supports each identifier or synonym assignment?","id":"structure-controls-name-resolution-q02","kind":"provenance"}]}]},{"id":"neighboring-arsenic-entities","name":"Neighboring arsenic entities","description":"Separates salts, protonation states, and chemically transformed arsenic species.","findings":[{"id":"salt-and-species-boundaries","name":"Salt and species boundaries","description":"Dissolved speciation belongs to sample state; an independently supplied salt or different oxidation-state compound needs an explicit related-entity link.","questions":[{"text":"Was the material supplied as free acid, a named methylarsonate salt, or an unresolved mixture?","id":"salt-and-species-boundaries-q01","kind":"boundary"},{"text":"What evidence distinguishes MMA(V) from MMA(III), dimethylated arsenic, and inorganic arsenic?","id":"salt-and-species-boundaries-q02","kind":"measurement"}]}]}]},{"id":"composition-and-physicochemical-state","name":"Composition and physicochemical state","description":"Describes the actual material and the conditions under which its properties are meaningful.","layers":[{"id":"batch-composition","name":"Batch composition","description":"Records target assay, moisture, counterions, and relevant impurities.","findings":[{"id":"purity-needs-species-evidence","name":"Purity needs species evidence","description":"Target assay should be distinguished from total arsenic content and accompanied by evidence about other arsenic species.","questions":[{"text":"What is the methylarsonic acid assay, its uncertainty, and its dry or as-received basis?","id":"purity-needs-species-evidence-q01","kind":"measurement"},{"text":"Which arsenic impurities, counterions, and water content were measured rather than assumed absent?","id":"purity-needs-species-evidence-q02","kind":"measurement"}]}]},{"id":"phase-and-solution-equilibria","name":"Phase and solution equilibria","description":"Connects physical-property observations and acid-base interpretations to experimental conditions.","findings":[{"id":"condition-qualified-properties","name":"Condition-qualified properties","description":"Solubility, thermal transitions, and aqueous protonation assignments require their own conditions and evidence.","questions":[{"text":"Which phase, solubility, melting, boiling, or decomposition observations are supported, at what temperature and pressure?","id":"condition-qualified-properties-q01","kind":"measurement"},{"text":"Which measured pH and supported dissociation constants justify the proposed aqueous species distribution?","id":"condition-qualified-properties-q02","kind":"measurement"}]}]}]},{"id":"speciation-evidence-and-transformation","name":"Speciation evidence and transformation","description":"Determines whether an analytical result identifies the target and preserves the meaning of the original sample.","layers":[{"id":"analytical-specificity","name":"Analytical specificity","description":"Assesses separation, identification, calibration, and reporting basis.","findings":[{"id":"target-specific-quantification","name":"Target-specific quantification","description":"Quantification requires evidence that the reported signal belongs to the intended methylated arsenic species.","questions":[{"text":"How does the validated method distinguish the target from coeluting arsenic species in this matrix?","id":"target-specific-quantification-q01","kind":"measurement"},{"text":"Which reference standard, recovery evidence, quantification limit, and concentration basis support the result?","id":"target-specific-quantification-q02","kind":"provenance"}]}]},{"id":"sample-history-and-conversion","name":"Sample history and conversion","description":"Tracks changes that could separate measured speciation from the original material.","findings":[{"id":"preservation-requires-validation","name":"Preservation requires validation","description":"Possible oxidation-state or methylation changes should be evaluated from matrix-specific evidence rather than presumed absent.","questions":[{"text":"What preservation, storage, and extraction history could have altered the measured arsenic species?","id":"preservation-requires-validation-q01","kind":"provenance"},{"text":"What stability evidence or repeat analysis is needed before treating this result as representative of the original sample?","id":"preservation-requires-validation-q02","kind":"action"}]}]}]},{"id":"hazards-and-permitted-actions","name":"Hazards and permitted actions","description":"Relates the identified material and its condition to evidence-based handling and jurisdiction-specific constraints.","layers":[{"id":"hazard-evidence-and-exposure","name":"Hazard evidence and exposure","description":"Connects classification and exposure criteria to chemical identity, sample form, and route.","findings":[{"id":"classification-applicability","name":"Classification applicability","description":"The model should distinguish evidence for the free acid from evidence for other arsenicals or formulated mixtures.","questions":[{"text":"Which current GHS classification and safety data record explicitly cover this identity and sample composition?","id":"classification-applicability-q01","kind":"provenance"},{"text":"Does an applicable exposure limit cover this arsenic species, and what route, averaging period, units, and arsenic basis does it use?","id":"classification-applicability-q02","kind":"boundary"}]}]},{"id":"use-and-waste-decisions","name":"Use and waste decisions","description":"Supports concrete handling, use, and disposal decisions without importing permissions from related products.","findings":[{"id":"action-specific-authority","name":"Action-specific authority","description":"A proposed action requires records applicable to the material, intended use, and jurisdiction.","questions":[{"text":"Which verified requirements govern containment, storage compatibility, and waste routing for this sample?","id":"action-specific-authority-q01","kind":"action"},{"text":"Does any claimed use authorization apply to the free acid itself, a methylarsonate salt, or a specific formulated product?","id":"action-specific-authority-q02","kind":"boundary"}]}]}]},{"id":"evidence-and-external-alignment","name":"Evidence and external alignment","description":"What the world already says about this thing, gathered so the model can be checked against it.","layers":[{"id":"reported-evidence","name":"Reported evidence","description":"Findings from the breadth pass, kept separate from the structural claims.","findings":[{"id":"evidence-confidence-notes","name":"Check these first","description":"Recalled without web access and unsourced; every item is a lead to verify.","questions":[{"text":"Which of these check these first hold for the sense of methyl arsonic acid this model covers, and on what evidence?","id":"evidence-confidence-notes-q01","kind":"provenance"}]},{"id":"evidence-identifiers","name":"Identifiers and schemes","description":"Recalled without web access and unsourced; every item is a lead to verify.","questions":[{"text":"Which of these identifiers and schemes hold for the sense of methyl arsonic acid this model covers, and on what evidence?","id":"evidence-identifiers-q01","kind":"provenance"}]},{"id":"evidence-real-world-use","name":"Real-world use","description":"Recalled without web access and unsourced; every item is a lead to verify.","questions":[{"text":"Which of these real-world use hold for the sense of methyl arsonic acid this model covers, and on what evidence?","id":"evidence-real-world-use-q01","kind":"provenance"}]},{"id":"evidence-measurements","name":"Typical measurements","description":"Recalled without web access and unsourced; every item is a lead to verify.","questions":[{"text":"Which of these typical measurements hold for the sense of methyl arsonic acid this model covers, and on what evidence?","id":"evidence-measurements-q01","kind":"provenance"}]},{"id":"evidence-failure-modes-and-hazards","name":"Failure modes and hazards","description":"Recalled without web access and unsourced; every item is a lead to verify.","questions":[{"text":"Which of these failure modes and hazards hold for the sense of methyl arsonic acid this model covers, and on what evidence?","id":"evidence-failure-modes-and-hazards-q01","kind":"provenance"}]},{"id":"evidence-neighbours","name":"Neighbouring kinds and how to tell them apart","description":"Recalled without web access and unsourced; every item is a lead to verify.","questions":[{"text":"Which of these neighbouring kinds and how to tell them apart hold for the sense of methyl arsonic acid this model covers, and on what evidence?","id":"evidence-neighbours-q01","kind":"provenance"}]}]}]}]},"agentConduct":{"may":["Identify methylarsonic acid and its salts in records, products or monitoring reports.","Explain its arsenic content and the rules that apply, citing official sources."],"mustNot":["Provide guidance on obtaining or using it to poison people or animals.","Recommend its use as a herbicide where approval has been withdrawn.","Advise disposal that releases arsenic to soil or water.","Treat organic arsenic compounds as harmless without evidence."],"requiresHuman":["Disposal of old stocks or remediation of contaminated land.","Responding to a suspected poisoning, which needs emergency medical services."]},"ethics":{"considerations":["Arsenic compounds persist in soil and can reach food and water.","Past use on fields, golf courses and roadsides has left contamination that affects communities."],"affectedParties":["Communities near treated land","Workers","Wildlife"]},"owners":{"steward":"The holder of any stock; environmental and pesticide authorities regulate it.","roles":[],"masterSystems":["Pesticide authorization registers","Contaminated land registers"]},"relations":[{"target":"Q11751651","type":"parent","note":"registry parent class"}],"interaction":{"identity":{"applicability":"required","items":["Vercy registry: vr.tr.methyl-arsonic-acid","Wikidata: Q1976186 (https://www.wikidata.org/wiki/Q1976186)"]},"properties":{"applicability":"required","items":["Chemical identity: Verified free acid; salt-related material; unresolved methylated arsenic identity","Arsenic oxidation state: V for target identity; measured III fraction; unresolved","Assay and purity basis: Mass percent, with as-received or dry basis and assay method","Arsenic impurity profile: mg/kg or molar fraction for individually identified arsenic species","Water content: Mass percent with measurement method","Physical and thermal state: Observed phase; temperature in °C; pressure in kPa; melting or decomposition evidence","Aqueous acid-base condition: pH, temperature in °C, ionic strength in mol/L, and supported species fractions","Target concentration: mol/L, mg/L as methylarsonic acid, or mg/L as As; basis required","Sample transformation history: Links to collection, preservation, storage, extraction, and analysis records","Hazard and regulatory applicability: Dated classification, jurisdiction, exact substance or mixture, exposure route, and concentration basis"]},"recognition":{"applicability":"required","items":["A white crystalline solid; salts appear in formulated herbicide products, so labels settle identity.","Old containers may carry withdrawn herbicide names."]},"capabilities":{"applicability":"required","items":["Resolve a supplied chemical name or identifier against the free-acid structure and flag salt or oxidation-state ambiguity.","Assess whether a batch is suitable for a specified analytical or research use from its assay and impurity evidence.","Compare concentrations after explicitly reconciling compound-mass, arsenic-mass, and molar reporting bases.","Select a validated speciation analysis capable of distinguishing the target from relevant arsenic interferents.","Evaluate whether sample preservation and storage support the reported chemical state.","Determine handling, containment, and waste-routing requirements from verified applicable records."]},"hazards":{"applicability":"required","items":["Can convert in the environment to more toxic inorganic arsenic.","Toxic if swallowed and harmful to aquatic life.","Contaminates soil for long periods."]},"interfaces":{"applicability":"required","items":["The Globally Harmonized System of Classification and Labelling of Chemicals, published by the United Nations, provides the framework for communicating chemical hazards through labels and safety data sheets.","The REACH Regulation, issued by the European Parliament and the Council of the European Union, governs applicable manufacture, import and supply obligations for this substance in the European Union."]},"context":{"applicability":"required","items":["Methylarsonic acid is encountered in analytical chemistry and research on arsenic metabolism and environmental transformation.","It is relevant to investigations of arsenic compounds in water, soil and biological samples, where the acid and its salts require careful distinction."]}},"sources":[{"title":"Wikidata item Q1976186: methyl arsonic acid","url":"https://www.wikidata.org/wiki/Q1976186","note":"identity and sense of the item"},{"title":"Wikipedia: Methylarsonic acid","url":"https://en.wikipedia.org/wiki/Methylarsonic_acid","note":"general description of the item"}],"openQuestions":["Which primary measurements establish dissociation constants and solubility across relevant temperature and ionic-strength conditions?","What reliable thermal data distinguish melting from decomposition, and is a meaningful boiling point available?","Which current jurisdiction-specific GHS classifications and exposure limits explicitly apply to methylarsonic acid rather than broader arsenic categories?","Which preservation and analytical methods demonstrate adequate MMA(V)/MMA(III) discrimination and stability in the intended sample matrices?","What impurity limits and reference-material certification are necessary for each intended grade or analytical use?"],"resources":{"spec":"/models/things/publications/thing-q1976186/spec.json"},"provenance":{"origin":"thing registry research (pass 2)","builtFrom":["models/things/publications/thing-q1976186/spec.json"],"providers":["Codex"],"researchStatus":"unreviewed","generatedAt":"2026-09-12T11:17:29Z","builder":"tools/build_cards.py@1.0.0"},"completeness":{"sections":{"classifiers":"filled","whatItIs":"filled","purpose":"filled","distinguishingFeatures":"filled","structure":"filled","agentConduct":"filled","ethics":"filled","owners":"filled","relations":"filled","interaction.identity":"filled","interaction.properties":"filled","interaction.recognition":"filled","interaction.capabilities":"filled","interaction.hazards":"filled","interaction.interfaces":"filled","interaction.context":"filled","sources":"filled"},"notes":{"_gate":"Published through the thing publication gate 1.0 on 2026-10-07T10:10:28+00:00: completeness 1.00; sense: Wikidata description; 2 live sources; review by codex: pass"},"score":1.0}}