{"schema":"https://ver.cy/schemas/card/1.0.0","id":"vr.tr.monosodium-methyl-arsenate","code":"thing-q3066718","url":"https://ver.cy/models/thing/q3066718/","name":"monosodium methyl arsenate","alternateNames":[],"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":"Monosodium methyl arsenate (MSMA) is the monosodium salt of methylarsonic acid, a pentavalent organoarsenic compound used as a herbicide.","purpose":"Enable an agent to identify monosodium methyl arsenate, assess the composition and condition of a particular material, and determine which handling or use decisions require further evidence.","scope":{"in":["MSMA identity, synonyms, identifiers and boundaries with related arsenic compounds","Salt stoichiometry, hydration, purity and arsenic-containing impurities","Solid or dissolved material state and condition-dependent physical properties","Analytical discrimination between MSMA, other methylated arsenic species and inorganic arsenic","Substance hazards, environmental transformations and jurisdiction-specific constraints"],"out":["Commercial herbicide formulations, co-formulants and packaging specifications","Manufacturing routes and production equipment","Field application schedules, spraying operations and crop-management plans","Clinical diagnosis and treatment of arsenic exposure","Complete models of methanearsonic acid, disodium methanearsonate and inorganic arsenic","Site remediation engineering and waste-treatment plant operation"],"boundaries":[]},"distinguishingFeatures":["Resolve the registry wording to monosodium methanearsonate rather than inferring structure from the word arsenate; PubChem identifies this substance as CID 23664719 with formula CH4AsNaO3. [PubChem](https://pubchem.ncbi.nlm.nih.gov/compound/Monosodium-methanearsonate)","Verify a methyl group directly bonded to arsenic, distinguishing the methanearsonate identity from inorganic arsenates and a possible methyl ester interpretation.","Verify one sodium equivalent per methanearsonate unit in the declared salt, distinguishing MSMA from disodium methanearsonate and the free acid.","Use species-resolved evidence to distinguish the intended pentavalent monomethyl arsenic identity from dimethylated or trivalent arsenic species; total arsenic alone is insufficient.","Distinguish the identified substance from a product containing it: EPA describes MSMA as an organic arsenical herbicide, but product identity and permitted use require separate records. [EPA](https://www.epa.gov/ingredients-used-pesticide-products/monosodium-methanearsonate-msma-organic-arsenical)"],"structure":{"bundles":[{"id":"msma-identity","name":"MSMA identity","description":"Resolve the registry name to a defined monosodium methanearsonate identity.","layers":[{"id":"name-structure-resolution","name":"Name and structure resolution","description":"Connect names and identifiers to the intended chemical structure.","findings":[{"id":"registry-name-mapping","name":"Registry name mapping","description":"Record the evidence that the registry label denotes MSMA and retain alternative wording as traceable synonyms.","questions":[{"text":"Which authoritative identity record establishes that this registry label denotes monosodium methanearsonate?","id":"registry-name-mapping-q01","kind":"definition"},{"text":"Which CAS, PubChem and EC identifiers refer to the same chemical form rather than a hydrate or mixture?","id":"registry-name-mapping-q02","kind":"provenance"}]}]},{"id":"neighboring-arsenic-identities","name":"Neighboring arsenic identities","description":"Define the structural and stoichiometric tests that separate MSMA from related compounds.","findings":[{"id":"salt-and-species-boundaries","name":"Salt and species boundaries","description":"Distinguish monosodium salt identity from free acid, disodium salt, inorganic arsenic and other methylated species.","questions":[{"text":"What evidence establishes methyl-to-arsenic connectivity and the intended arsenic oxidation state?","id":"salt-and-species-boundaries-q01","kind":"measurement"},{"text":"How is monosodium salt identity distinguished from disodium methanearsonate when dissolved species depend on solution conditions?","id":"salt-and-species-boundaries-q02","kind":"boundary"}]}]}]},{"id":"lot-composition","name":"Lot composition","description":"Represent the actual material associated with the nominal MSMA identity.","layers":[{"id":"assay-and-hydration","name":"Assay and hydration","description":"Establish the basis used to quantify MSMA in a lot.","findings":[{"id":"comparable-content","name":"Comparable content","description":"Keep salt mass, acid equivalent, elemental arsenic and water content distinguishable.","questions":[{"text":"Is the reported content expressed as MSMA salt, methanearsonic acid equivalent or elemental arsenic?","id":"comparable-content-q01","kind":"measurement"},{"text":"Does the assay use an anhydrous, hydrated, dry-mass or as-received basis, and what evidence supports it?","id":"comparable-content-q02","kind":"provenance"}]}]},{"id":"impurities-and-grade","name":"Impurities and grade","description":"Describe composition that affects suitability beyond nominal active content.","findings":[{"id":"lot-acceptance-evidence","name":"Lot acceptance evidence","description":"Require explicit impurity specifications and separate technical material from formulated products.","questions":[{"text":"What inorganic arsenic and other arsenic-species impurities were measured, with what quantification limits?","id":"lot-acceptance-evidence-q01","kind":"measurement"},{"text":"Which lot-specific specification determines suitability for the intended use?","id":"lot-acceptance-evidence-q02","kind":"action"},{"text":"At what point do co-formulants require a linked product model rather than description as an MSMA material grade?","id":"lot-acceptance-evidence-q03","kind":"boundary"}]}]}]},{"id":"physical-state-and-stability","name":"Physical state and stability","description":"Relate measured properties and changes to a defined MSMA material and its conditions.","layers":[{"id":"conditioned-properties","name":"Conditioned properties","description":"Record phase, solubility and thermal observations with the conditions needed to interpret them.","findings":[{"id":"state-specific-constants","name":"State-specific constants","description":"Attach physical measurements to the tested chemical form and matrix.","questions":[{"text":"Which solubility measurements apply to the identified MSMA form, solvent, temperature and pH?","id":"state-specific-constants-q01","kind":"measurement"},{"text":"Do reported thermal values describe melting, dehydration or decomposition, and is a boiling point actually established?","id":"state-specific-constants-q02","kind":"measurement"}]}]},{"id":"storage-related-change","name":"Storage-related change","description":"Connect changes in stored material to evidence for continued suitability.","findings":[{"id":"reassessment-triggers","name":"Reassessment triggers","description":"Define observations that require renewed assay or speciation instead of assuming stability.","questions":[{"text":"What measured changes in water content, pH, appearance or species profile occur under the documented storage conditions?","id":"reassessment-triggers-q01","kind":"measurement"},{"text":"Which changes trigger quarantine, reanalysis or rejection under the applicable material specification?","id":"reassessment-triggers-q02","kind":"action"}]}]}]},{"id":"arsenic-analysis-and-fate","name":"Arsenic analysis and fate","description":"Track what analytical results establish and how arsenic species may change after release.","layers":[{"id":"species-resolved-analysis","name":"Species-resolved analysis","description":"Establish whether a method can distinguish the target species from relevant alternatives.","findings":[{"id":"analytical-specificity","name":"Analytical specificity","description":"Document species coverage, sample preservation and analytical uncertainty.","questions":[{"text":"Which validated method distinguishes monomethyl arsenic species from inorganic and dimethylated arsenic in this matrix?","id":"analytical-specificity-q01","kind":"measurement"},{"text":"How do preservation, extraction and holding time affect the species profile measured in the sample?","id":"analytical-specificity-q02","kind":"provenance"},{"text":"Does species-resolved arsenic reconcile with independently measured total arsenic within stated uncertainty?","id":"analytical-specificity-q03","kind":"measurement"}]}]},{"id":"environmental-transformation","name":"Environmental transformation","description":"Frame research into transformation, retention and transport in the receiving environment.","findings":[{"id":"parent-and-residue-accounting","name":"Parent and residue accounting","description":"Keep disappearance of the starting species separate from removal of arsenic from the system.","questions":[{"text":"Which transformation products and rates are supported for the relevant soil or water conditions?","id":"parent-and-residue-accounting-q01","kind":"provenance"},{"text":"What measurements distinguish transformation from sorption, leaching or physical export of arsenic?","id":"parent-and-residue-accounting-q02","kind":"measurement"}]}]}]},{"id":"hazards-and-permitted-actions","name":"Hazards and permitted actions","description":"Connect MSMA-specific evidence to handling, use and disposal decisions.","layers":[{"id":"hazard-evidence","name":"Hazard evidence","description":"Identify classifications and exposure constraints that apply to the actual material.","findings":[{"id":"applicable-hazard-record","name":"Applicable hazard record","description":"Separate evidence for MSMA from evidence for impurities, transformation products and formulations.","questions":[{"text":"Which current classification applies to this chemical form and purity, and which authority or supplier supports it?","id":"applicable-hazard-record-q01","kind":"provenance"},{"text":"Does each proposed exposure limit explicitly cover MSMA or the relevant arsenic category, and on what mass basis?","id":"applicable-hazard-record-q02","kind":"boundary"},{"text":"What handling controls follow from the actual physical form, exposure route and supported hazard record?","id":"applicable-hazard-record-q03","kind":"action"}]}]},{"id":"authorization-and-disposition","name":"Authorization and disposition","description":"Link intended activities to dated, jurisdiction-specific controlling records.","findings":[{"id":"use-and-disposal-gates","name":"Use and disposal gates","description":"Require the relevant product label or waste determination before concluding that an activity is permitted.","questions":[{"text":"Which current authorization and product label govern the proposed MSMA use in the specified jurisdiction and location?","id":"use-and-disposal-gates-q01","kind":"action"},{"text":"Which waste characterization and local rules determine the allowed disposition of this material or its arsenic-containing residues?","id":"use-and-disposal-gates-q02","kind":"action"}]}]}]},{"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 monosodium methyl arsenate 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 monosodium methyl arsenate this model covers, and on what evidence?","id":"evidence-identifiers-q01","kind":"provenance"}]},{"id":"evidence-standards-and-regulation","name":"Standards and regulation","description":"Recalled without web access and unsourced; every item is a lead to verify.","questions":[{"text":"Which of these standards and regulation hold for the sense of monosodium methyl arsenate this model covers, and on what evidence?","id":"evidence-standards-and-regulation-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 monosodium methyl arsenate 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 monosodium methyl arsenate 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 monosodium methyl arsenate this model covers, and on what evidence?","id":"evidence-failure-modes-and-hazards-q01","kind":"provenance"}]},{"id":"evidence-regional-variation","name":"Regional variation","description":"Recalled without web access and unsourced; every item is a lead to verify.","questions":[{"text":"Which of these regional variation hold for the sense of monosodium methyl arsenate this model covers, and on what evidence?","id":"evidence-regional-variation-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 monosodium methyl arsenate this model covers, and on what evidence?","id":"evidence-neighbours-q01","kind":"provenance"}]}]}]}]},"agentConduct":{"may":["Explain MSMA as an organoarsenic herbicide and its registration status in a jurisdiction, from official sources.","Report label restrictions and hazards from registered product labels."],"mustNot":["Recommend using it where it is cancelled, restricted or unregistered.","Advise applying it near water, food crops or homes against label restrictions.","Dispose of arsenic-containing residues into drains, soil or waters.","Present arsenic herbicides as harmless because the arsenic is organic."],"requiresHuman":["Any decision to apply arsenical herbicides on land the agent manages."]},"ethics":{"considerations":["Arsenic can convert to more toxic forms and contaminate soil and groundwater.","Applicators and nearby residents bear the exposure."],"affectedParties":["Applicators and farm workers","Residents relying on groundwater","Wildlife"]},"owners":{"steward":"The registered holder and the user; pesticide regulators control registration and use.","roles":[],"masterSystems":["National pesticide registers"]},"relations":[{"target":"Q11173","type":"parent","note":"registry parent class"}],"interaction":{"identity":{"applicability":"required","items":["Vercy registry: vr.tr.monosodium-methyl-arsenate","Wikidata: Q3066718 (https://www.wikidata.org/wiki/Q3066718)"]},"properties":{"applicability":"required","items":["Chemical identity resolution: Registry id linked to verified structure, preferred name, synonyms, CAS number, PubChem CID and applicable EC identifier","Sodium-to-arsenic stoichiometry: mol Na/mol As, with analytical method and matrix","Hydration and water content: mol H2O/mol salt where established; mass % water","MSMA assay and reporting basis: mass %, g/L or mol/L; explicitly as salt, acid equivalent or elemental arsenic","Arsenic species profile: mg As/kg or mg As/L by identified species, with detection limits","Physical state and sample matrix: Solid, aqueous solution or other documented matrix; temperature and pressure","Solution acidity: pH at stated temperature and concentration","Solubility and thermal behavior: Solubility in g/L with solvent and temperature; thermal events in °C with method and decomposition annotation","Hazard classification and exposure constraints: Authority-specific GHS classification and applicable exposure limits, including chemical coverage, units and averaging period","Regulatory applicability: Jurisdiction, effective date, substance or product authorization, intended use and controlling document"]},"recognition":{"applicability":"required","items":["Identified by container label, chemical name and identifier, and certificate of analysis rather than by appearance alone."]},"capabilities":{"applicability":"required","items":["Match a supplier or laboratory record to MSMA while flagging conflicting names, structures or identifiers.","Compare material lots after reconciling hydration and concentration reporting bases.","Specify identity and arsenic-speciation measurements needed to accept, quarantine or reassess a sample.","Assess whether observed precipitation, water change or assay drift requires renewed characterization.","Link a proposed use to the applicable product authorization and jurisdictional restrictions.","Route material or residues to handling and disposal decisions supported by their measured composition."]},"hazards":{"applicability":"required","items":["Arsenic contamination of soil and groundwater.","Toxicity from skin contact or ingestion.","Harm to non-target plants and animals."]},"interfaces":{"applicability":"required","items":["Globally Harmonized System of Classification and Labelling of Chemicals (GHS), United Nations."]},"context":{"applicability":"required","items":["Monosodium methyl arsenate is encountered as an active ingredient in herbicide formulations and in records of agricultural and turf weed control.","It is also relevant to environmental monitoring of arsenic associated with past or present herbicide use.","Assessment distinguishes the identified compound from other arsenic species and considers the formulation and locally permitted uses."]}},"sources":[{"title":"Wikidata item Q3066718: monosodium methyl arsenate","url":"https://www.wikidata.org/wiki/Q3066718","note":"identity and sense of the item"},{"title":"Wikipedia: Monosodium methyl arsonate","url":"https://en.wikipedia.org/wiki/Monosodium_methyl_arsonate","note":"general description of the item"}],"openQuestions":["Which CAS and EC identifiers, hydrate distinctions and structural records definitively resolve the registry wording to the intended MSMA substance?","Which primary measurements establish solubility, thermal behavior and storage stability for specified MSMA forms rather than commercial formulations?","Which validated analytical methods and impurity specifications adequately distinguish MSMA from inorganic arsenic and other methylated species in relevant lots?","Which environmental transformation products, rates and transport behavior are supported under the intended receiving conditions?","Which current hazard classifications, exposure limits, product permissions and waste rules apply in the intended jurisdiction?"],"resources":{"spec":"/models/things/publications/thing-q3066718/spec.json"},"provenance":{"origin":"thing registry research (pass 2)","builtFrom":["models/things/publications/thing-q3066718/spec.json"],"providers":["Codex"],"researchStatus":"unreviewed","generatedAt":"2026-09-12T11:23:50Z","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 2026-10-07T10:10:29+00:00: completeness 1.00; sense: Wikidata description; 2 live sources; review by codex: pass"},"score":1.0}}