sulfur dioxide
Enable an agent to identify sulfur dioxide, assess its composition and condition, and determine whether a proposed use, transfer, exposure or release is acceptable under documented requirements.
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 identify sulfur dioxide, assess its composition and condition, and determine whether a proposed use, transfer, exposure or release is acceptable under documented requirements.
Sulfur dioxide (SO₂) is a molecular compound of sulfur and oxygen, with sulfur in oxidation state +4, that is a colorless, pungent, nonflammable gas at ordinary room temperature and atmospheric pressure.
It can be Match a sample, supplier lot or monitoring result to the sulfur dioxide identity and its material context.; Evaluate purity, moisture and grade evidence against a specified use.; Interpret phase and inventory from documented temperature, pressure and composition.; Compare air measurements with applicable criteria using compatible units and averaging periods.; Assess a proposed containment or transfer arrangement against documented compatibility and hazard requirements.; Trace measured or reported sulfur dioxide through dissolution or transformation while preserving distinctions between species and reporting equivalents..
Distinguishing features
The identified molecule must contain one sulfur atom and two oxygen atoms; sulfur trioxide has three oxygen atoms and requires a separate identity.
A molecular sulfur dioxide measurement must be distinguished from measurements reporting sulfite, bisulfite or an aggregate result expressed as SO2 equivalents.
A sample described as sulfur dioxide must identify whether it is the supplied substance or a component of a carrier gas, solution or formulated product.
Gas versus liquefied sulfur dioxide is a condition-dependent state distinction, not a different chemical identity.
Odour or an undifferentiated sulfur signal is insufficient identification; the analytical method must distinguish sulfur dioxide from other sulfur-containing compounds.
Scope
+ Molecular identity and identifiers for sulfur dioxide
+ Purity, grade, moisture and relevant impurities
+ Gas and liquid states under recorded temperature and pressure
+ Dissolution, aqueous speciation and chemical transformation boundaries
+ Substance hazards, exposure measurements and applicable classification records
+ Suitability for documented uses, containment and release controls
- Complete formulations of foods, wines and other products containing sulfur dioxide
- Sulfite and bisulfite salts as independently registered substances
- Sulfur trioxide, sulfuric acid and downstream sulfate aerosol as separate substances
- Design and operation of combustion plants, scrubbers and manufacturing processes
- Design, certification and maintenance of cylinders, valves and monitoring instruments
- Clinical diagnosis and treatment of exposure-related illness
Characteristics
- Chemical and regulatory identity
- SO2; verified CAS number, PubChem CID and EC number with source records Connects analytical, supplier and regulatory records to the same substance.
- Material context
- Supplied substance; gas-mixture component; dissolved component; product constituent Prevents a containing product or mixture from being mistaken for pure sulfur dioxide.
- Assay and impurity profile
- Mass fraction or mole fraction of SO2; named impurities in compatible units; method and uncertainty Determines whether the material meets the requirements of an intended use.
- Declared grade
- Supplier grade and referenced specification, with certificate and lot A grade claim requires evidence beyond the substance name.
- Moisture content
- Mass fraction, ppm by mass or dew point with measurement conditions Moisture affects aqueous chemistry and assessment of materials compatibility.
- Thermodynamic condition
- Gas, liquid or two-phase; temperature in K or °C; absolute pressure in Pa or bar Supports interpretation of storage conditions, inventory and potential release behaviour.
- Phase-property reference
- Melting and boiling temperatures with pressure; vapour pressure and density with temperature Allows condition-specific assessment without treating reference constants as universal operating values.
- Air concentration
- ppm by volume or mg/m³; temperature, pressure, location, averaging period and method Makes measurements interpretable against the correct exposure or ambient-air criterion.
- Aqueous analytical fraction
- Method-defined molecular, free, bound or total sulfur dioxide; matrix and pH Prevents analytically different fractions from being treated as interchangeable quantities.
- Applicable hazard and limit records
- Links to current safety data, jurisdiction-specific GHS implementation, exposure limits and use restrictions Preserves the authority, date and applicability of requirements used in decisions.
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 5 bundles · 9 layers · 17 findings · 25 questions.
Sulfur dioxide identity and grade Establishes which substance and material form a record refers to and whether its quality is evidenced.
The name sulfur dioxide can label a substance, a mixture component or an analytical reporting basis; these contexts support different decisions.
Molecular and registry identity
Connects SO2 to verified identifiers and resolves neighbouring substance boundaries.
Identity evidence and species boundary
Record the evidence identifying molecular sulfur dioxide and distinguish it from other sulfur oxides and sulfite salts.
- Which authoritative records establish the CAS number, PubChem CID and EC number for the SO2 identity represented here? provenance
- Does this record identify sulfur dioxide itself, a containing material or a quantity expressed as SO2 equivalents? boundary
Lot composition and use grade
Captures assay, moisture, impurities and the specification supporting a grade claim.
Verified quality for intended use
Treat grade as a specification-backed claim about a lot, rather than a consequence of its chemical identity.
- What SO2 assay, moisture content and relevant impurity concentrations were measured for this lot, by which methods? measurement
- Which documented specification makes this lot suitable for its proposed food, analytical or industrial use? action
Sulfur dioxide phase and containment Relates gaseous or liquefied material to temperature, pressure, inventory and contact conditions.
A sulfur dioxide quantity cannot be assessed for storage or transfer from its name or volume alone.
Phase and property basis
Establishes physical state using measured conditions and sourced property data.
Condition-dependent physical state
Record phase, temperature and absolute pressure together, retaining the conditions attached to reference properties.
- At the recorded composition, temperature and absolute pressure, is the material gaseous, liquid or two-phase? measurement
- Which sources and validity ranges support the melting point, boiling point, vapour pressure and density used in this assessment? provenance
Contact materials and release context
Links the substance's condition to compatibility and possible loss of containment.
Moisture-sensitive containment assessment
Assess contact materials and release controls using the actual moisture, phase and operating conditions.
- What compatibility evidence covers the wetted materials and seals at the stated sulfur dioxide moisture content, temperature and pressure? provenance
- What documented containment, detection and isolation requirements must be satisfied before this quantity is stored or transferred? action
Aqueous speciation and transformation Preserves chemical and analytical distinctions when sulfur dioxide dissolves, binds or undergoes reaction.
Dissolved sulfur dioxide, free or total SO2 results, and transformed sulfur species cannot be substituted for one another without a defined basis.
Dissolved species and analytical fractions
Records matrix conditions and method definitions governing aqueous sulfur dioxide reporting.
Meaning of an aqueous SO2 result
Keep molecular, free, bound and total reporting categories tied to the analytical method and sample matrix.
- What does the reported molecular, free, bound or total SO2 fraction include under the method used? definition
- What pH, temperature, matrix composition and sample handling conditions accompany the result? measurement
Reaction and accounting boundaries
Tracks when sulfur dioxide becomes another species and how sulfur quantities remain comparable.
Transformation without identity collapse
Record dissolution and reaction relationships while assigning resulting substances their own identities.
- Which observed or evidenced reaction changes SO2 into another species, and where does this model hand responsibility to that species' model? boundary
- Are quantities reported as actual SO2 mass, sulfur mass or SO2 equivalents, and what documented conversion relates them? measurement
Sulfur dioxide hazards and permitted actions Connects hazard evidence and measured exposure to context-specific decisions about use and release.
Sulfur dioxide decisions require distinctions between substance hazards, workplace exposure, ambient pollution and permitted product uses.
Hazard classification and air exposure
Keeps classification records and concentration comparisons tied to their scope and measurement basis.
Applicable hazard and exposure evidence
Use sourced classifications and limits, preserving material form, jurisdiction, averaging period and measurement uncertainty.
- Which current safety data and jurisdictional classification records apply to this sulfur dioxide material and supplied form? provenance
- Which workplace or ambient-air criterion applies to this measurement, and do units, reference conditions and averaging periods match? measurement
Use and release decision
Determines whether a proposed action has the necessary material evidence and applicable authorisation.
Context-specific action eligibility
Evaluate a proposed application or release against its specific requirements without treating one approval as universal.
- For the proposed use, what jurisdiction, product category, grade, quantity and labelling requirements apply? action
- What verified criteria govern the proposed emission, disposal or abatement outcome, and what evidence demonstrates compliance? 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 recall-based information; no sources were consulted.
- Verify current jurisdiction-specific hazard classifications, exposure limits, food permissions and labelling thresholds before regulatory use.
- Grade names are commercial distinctions rather than separate chemical species; purity, water content and impurity limits require supplier specifications.
- Which of these check these first hold for the sense of sulfur dioxide this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- Industrial-grade sulfur dioxide
- Food-grade sulfur dioxide
- High-purity sulfur dioxide
- Which of these kinds and varieties hold for the sense of sulfur dioxide 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 - 7446-09-5 - Identifies sulfur dioxide as a chemical substance.
- PubChem CID - 1119 - Compound record identifier.
- EC number - 231-195-2 - European chemical inventory identifier.
- UN dangerous goods number - UN 1079 - Transport identity for sulfur dioxide.
- European food additive E number - E220 - Food additive identity; does not establish that every grade or application is permitted.
- Which of these identifiers and schemes hold for the sense of sulfur dioxide 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 Economic Commission for Europe: Globally Harmonized System of Classification and Labelling of Chemicals provides the hazard classification framework.
- European Union: CLP Regulation governs classification, labelling and packaging.
- European Union: REACH Regulation governs chemical registration and associated obligations.
- United States Environmental Protection Agency: National Ambient Air Quality Standards regulate sulfur dioxide in outdoor air.
- United States Occupational Safety and Health Administration: workplace air contaminant standards include sulfur dioxide exposure limits.
- Which of these standards and regulation hold for the sense of sulfur dioxide this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Intermediate in sulfuric acid manufacture.
- Preservative and antioxidant in permitted food and beverage applications, including wine.
- Reducing and bleaching agent in pulp and other industrial processing.
- Reagent for removing residual chlorine from treated water.
- Feedstock for manufacturing sulfites and bisulfites.
- Which of these real-world use hold for the sense of sulfur dioxide 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 - Approximately 64.06 - g/mol
- Melting point of pure substance - Approximately -72.7 - °C
- Boiling point at 101.325 kPa - Approximately -10.0 - °C
- Relative gas density compared with air at equal temperature and pressure - Approximately 2.2 - dimensionless
- Which of these typical measurements hold for the sense of sulfur dioxide 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.
- Toxic by inhalation; exposure can cause severe respiratory irritation and lung injury.
- Can trigger bronchoconstriction, particularly in people with asthma.
- Contact with liquefied sulfur dioxide can cause frostbite; heated pressure containers can rupture.
- Dissolution in moisture produces acidic solutions that can damage tissue and corrode susceptible materials.
- Atmospheric oxidation contributes to sulfate particulate pollution and acid deposition.
- Which of these failure modes and hazards hold for the sense of sulfur dioxide this model covers, and on what evidence? provenance
Regional variation
Recalled without web access and unsourced; every item is a lead to verify.
- Workplace exposure limits, averaging periods and short-term limits differ among jurisdictions and issuing bodies.
- Permitted food uses, maximum concentrations and sulfite declaration requirements vary by jurisdiction and food category.
- Ambient air standards and industrial emission requirements vary among countries and regions.
- Which of these regional variation hold for the sense of sulfur dioxide 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.
- Sulfur trioxide - SO₃ contains three oxygen atoms per sulfur atom and sulfur in oxidation state +6, rather than +4.
- Sulfurous acid - H₂SO₃ is the conventional acid formula associated with aqueous sulfur dioxide chemistry; it is not synonymous with pure molecular SO₂.
- Sulfites and bisulfites - These contain sulfite or hydrogen sulfite ions, often as salts; sulfur dioxide is a neutral molecular substance, although they interconvert in aqueous equilibria.
- Sulfuric acid - H₂SO₄ is a distinct sulfur(VI) acid produced downstream of sulfur dioxide oxidation.
- Sulfur dioxide solution - An aqueous preparation has a concentration, pH and distribution of dissolved species; it is a mixture rather than the pure substance.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of sulfur dioxide this model covers, and on what evidence? provenance
What the second pass must settle
- Which authoritative identity records and condition-qualified physical-property sources should be adopted as the publication's reference set?
- Which impurities and moisture thresholds distinguish the sulfur dioxide grades relevant to the intended applications?
- Which aqueous matrices and analytical methods must be supported, and how does each define molecular, free, bound and total SO2?
- Which jurisdictions and use contexts determine the applicable hazard classifications, exposure limits, product restrictions and emission criteria?
- What sourced compatibility evidence is sufficient for dry versus moisture-containing sulfur dioxide across the intended storage and transfer conditions?