hydrogen sulfide
Enable an AI agent to identify hydrogen sulfide, assess its chemical and exposure state, and determine which handling, monitoring or treatment actions require verified controls.
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 AI agent to identify hydrogen sulfide, assess its chemical and exposure state, and determine which handling, monitoring or treatment actions require verified controls.
Hydrogen sulfide (H₂S) is a molecular compound of hydrogen and sulfur that is a colorless, highly toxic, flammable gas at ordinary ambient temperature and pressure, with a characteristic rotten-egg odor at low concentrations.
It can be Resolve a label or analytical result to hydrogen sulfide and flag unresolved identity or composition.; Compare sample composition and grade with an intended use's documented requirements.; Interpret H2S concentrations using explicit units, sampling conditions and measurement validity.; Assess whether changing solution or containment conditions requires renewed evaluation of H2S release.; Compare observations with verified, applicable hazard criteria and escalate when evidence or controls are inadequate.; Track hydrogen sulfide through transfer or treatment while distinguishing removal, conversion and relocation..
Distinguishing features
The molecular identity must resolve to H2S, rather than sulfur dioxide, elemental sulfur, an organosulfur compound or a sulfide salt.
A dissolved measurement must distinguish molecular H2S from hydrosulfide, sulfide ions and any analytically defined total sulfide result.
A mixture containing H2S remains a mixture; its bulk composition and commercial name do not establish that it is pure hydrogen sulfide.
An odor report alone does not establish identity, concentration or safe conditions; recognition requires a suitable analytical or documented identity basis.
A gaseous occurrence, a liquefied inventory and a dissolved occurrence share a substance identity but require different state and quantity descriptions.
Scope
+ Molecular identity, authoritative substance identifiers and distinctions from other sulfur compounds.
+ Purity, grade, impurities and hydrogen sulfide concentration in a specified medium.
+ Gas, liquid and dissolved states under recorded temperature, pressure and solution conditions.
+ Measurements of hydrogen sulfide, including sampling validity and instrument limitations.
+ Chemical compatibility, exposure and release hazards, and applicable classification records.
+ Formation, movement and transformation of hydrogen sulfide where these affect its current state.
- Complete composition and performance models for sour natural gas, biogas, wastewater and other mixtures containing hydrogen sulfide.
- Design and operation of wells, sewers, reactors, gas networks and treatment facilities.
- Medical diagnosis and treatment of exposed individuals.
- Detailed biology of organisms that produce, consume or respond to hydrogen sulfide.
- Construction and maintenance of detectors, ventilation systems and protective equipment.
- Execution of emergency rescue, disposal or industrial production procedures.
Characteristics
- Chemical identity
- Formula H2S; verified CAS, PubChem and EC identifiers with source and verification date Connects the material to the correct substance record without confusing related sulfur species or mixtures.
- Material grade and composition
- Purity as mol%, mass% or another explicit basis; impurity identities and concentrations; grade designation Determines whether a material meets an intended use and whether impurities alter compatibility or measurement.
- Physical state and conditions
- Gas, liquid, dissolved or multiphase; temperature in K or °C; absolute pressure in Pa, kPa or bar Makes phase descriptions and inventories interpretable and supports assessment of release behavior.
- Hydrogen sulfide concentration
- Gas: ppmv, mol% or mg/m³; solution: mol/L or mg/L; include medium, temperature, pressure and reporting basis Separates an actual H2S measurement from incompatible concentration units or aggregate sulfide measurements.
- Aqueous speciation conditions
- pH, temperature, salinity or ionic strength; measured or calculated H2S fraction with method Supports interpretation of dissolved sulfide and the potential for molecular H2S to enter a gas phase.
- Phase and partition properties
- Melting and boiling points in °C or K with pressure; vapor pressure with temperature; solubility and partition constants with explicit conventions Provides condition-specific evidence for phase changes and transfer between water and gas.
- Measurement validity
- Method, calibration status, detection and quantification limits, range, uncertainty, interferences, sample location and timestamp Prevents an invalid, stale or out-of-range reading from supporting a handling decision.
- Hazard and regulatory applicability
- Links to current classification, safety data, exposure limits and transport records; jurisdiction, physical form and effective date Ensures that restrictions and thresholds apply to the actual material and location.
- Exposure observation
- Concentration with duration, averaging period, sampling position and exposure population Allows an exposure observation to be compared with an appropriately matched reference.
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 19 findings · 32 questions.
H2S identity and material boundary Establishes what is being identified and whether the record describes the substance, a grade or an occurrence within a mixture.
Hydrogen sulfide, dissolved sulfide and H2S-containing products cannot be treated as interchangeable identities.
Molecular and regulatory identity
Connects H2S identity to independently verified reference records.
Verified H2S identity
Record the evidence that establishes hydrogen sulfide identity and the authoritative identifiers attached to it.
- What label, analytical evidence or reference record establishes that the species is H2S? definition
- Which authoritative records verify its CAS number, PubChem CID and EC number, and when were they checked? provenance
Grade and mixture boundary
Separates substance identity from purity specifications and containing materials.
Composition-qualified material
Describe purity, impurities and concentration without assigning the containing mixture's identity to H2S.
- Is this pure or technical-grade hydrogen sulfide, a certified gas mixture, or H2S occurring in another material? boundary
- What purity, water content and other impurities are documented, on which measurement basis? measurement
Phase, speciation and partition Describes the conditions governing physical state and the distinction between molecular H2S and other dissolved sulfide species.
A concentration or inventory is insufficient without knowing its phase, chemical form and potential transfer between media.
Physical state envelope
Records phase and the conditions supporting that assignment.
Conditioned phase properties
Attach pressure, temperature and reference conditions to phase assignments and physical constants.
- Which phases contain H2S, and what temperature and absolute pressure were measured for each? measurement
- Which read sources establish the applicable melting point, boiling point and vapor-pressure relationship, including their conditions? provenance
Dissolved speciation and gas transfer
Distinguishes aqueous molecular H2S from aggregate sulfide and evaluates transfer to a gas phase.
Aqueous H2S fraction
Make explicit whether dissolved H2S is measured directly or inferred from a broader sulfide result.
- Does the reported value represent molecular H2S, total dissolved sulfide or another operationally defined fraction? definition
- What pH, temperature, ionic conditions and equilibrium assumptions support any calculated molecular H2S fraction? measurement
- Would a proposed change in pH, temperature, pressure or agitation require reassessing transfer of H2S into the headspace? action
H2S detection and evidence quality Determines whether gas and liquid observations reliably describe the occurrence being assessed.
Odor, point measurements and aggregate sulfide assays provide different evidence and cannot substitute for one another.
Sampling and analysis
Connects the reported analyte and concentration to a suitable sampling and analytical method.
Representative H2S result
Record where and how the sample was obtained and whether collection or storage could change its H2S content.
- Where, when and in which medium was H2S sampled, and what spatial or temporal extent does the result represent? measurement
- How did the method address H2S loss, chemical transformation and interference during sampling, transport and analysis? provenance
Detector and interpretation limits
Captures the evidence needed to trust an instrument reading or interpret a non-detection.
Qualified detection status
Distinguish a valid measurement from an instrument fault, an untested range or a sensory observation.
- What calibration, functional-check, range and interference evidence supports this detector reading? provenance
- Does a reported zero mean below a stated detection limit, missing data, instrument failure or a valid quantified result? boundary
- What additional measurement is required if the only available evidence is an odor report or its absence? action
Exposure, ignition and handling constraints Links H2S observations and material state to verified hazard criteria and handling prerequisites.
An agent must assess exposure and physical hazards using applicable evidence before recommending an action involving H2S.
Exposure criteria and observations
Matches measured exposure to the correct reference and averaging period.
Applicable exposure comparison
Keep occupational limits, emergency criteria and instrument alarm settings distinct.
- Which current exposure limits or emergency criteria apply in this jurisdiction and setting, and what sources establish them? provenance
- Are concentration units, averaging period, sampling location and measurement uncertainty compatible with the proposed comparison? measurement
- What documented escalation is required when the applicable criterion is exceeded or the exposure state is unknown? action
Physical hazards and control prerequisites
Connects chemical classification, ignition conditions and containment state to permitted handling.
Evidence-based handling constraints
Record the specific prerequisites for an intended action using applicable safety and compatibility references.
- Which verified classifications, flammability data and pressure-related hazards apply to this physical form and composition? provenance
- Which verified material-compatibility, containment, ventilation and monitoring requirements apply to the intended transfer or use? action
Formation, fate and removal Tracks the origin of an H2S occurrence and what happens to it during release, transport or treatment.
A falling H2S reading can reflect transfer, dilution or chemical conversion; it does not by itself establish that a source or hazard has been eliminated.
Origin and release context
Links the occurrence to a documented source and conditions that may sustain or renew it.
Supported source attribution
Distinguish observed H2S from an inferred biological, geological, industrial or stored-material origin.
- What evidence identifies the source of this H2S occurrence, and which parts of the attribution remain inferred? provenance
- Which source conditions could sustain or renew H2S accumulation after an initial low reading? boundary
Transformation and treatment outcome
Distinguishes destruction of molecular H2S from capture or movement to another medium.
Accounted H2S fate
Record the evidence for removal and identify residual H2S, sulfur-containing products and transferred inventories.
- Was H2S chemically converted, captured, diluted or transferred to another phase, and what measurements support that conclusion? measurement
- Which residual materials or changed conditions require follow-up assessment for remaining H2S or renewed release? 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 description is recalled knowledge; no sources were consulted.
- Verify current jurisdiction-specific exposure limits, GHS classifications, and transport provisions for the actual supplied product.
- The listed kinds distinguish formulation or grade, not separate molecular species; aqueous composition depends on concentration, temperature, and pH.
- Which of these check these first hold for the sense of hydrogen sulfide 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 hydrogen sulfide
- Aqueous hydrogen sulfide solutions
- High-purity hydrogen sulfide grades
- Which of these kinds and varieties hold for the sense of hydrogen sulfide 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 - 7783-06-4 - Identifies hydrogen sulfide as a chemical substance.
- PubChem CID - 402 - Compound identifier for hydrogen sulfide.
- EC number - 231-977-3 - European chemical inventory identifier.
- UN number - 1053 - Dangerous-goods transport identifier for hydrogen sulfide; mixtures require their own classification assessment.
- Which of these identifiers and schemes hold for the sense of hydrogen sulfide 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.
- United Nations Recommendations on the Transport of Dangerous Goods, Model Regulations: transport classification framework.
- European Union Classification, Labelling and Packaging (CLP) Regulation: chemical classification and labeling requirements.
- US Occupational Safety and Health Administration (OSHA) Hazard Communication Standard: workplace hazard communication requirements.
- Which of these standards and regulation hold for the sense of hydrogen sulfide this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Feedstock for sulfur recovery from sour natural gas and refinery gas streams.
- Reagent for preparing metal sulfides.
- Sulfiding agent for certain industrial catalysts.
- Sulfur precursor in some semiconductor and thin-film manufacturing processes.
- Component of certified gas mixtures used to calibrate hydrogen sulfide detectors.
- Which of these real-world use hold for the sense of hydrogen sulfide 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 - 34.08 - g/mol
- Melting point of pure substance - Approximately -85.5 - °C
- Normal boiling point at approximately 101.3 kPa - Approximately -60.3 - °C
- Gas density relative to air at the same temperature and pressure - Approximately 1.19 - dimensionless
- Which of these typical measurements hold for the sense of hydrogen sulfide 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.
- Acute inhalation toxicity can cause rapid unconsciousness, respiratory failure, and death.
- Odor is an unreliable warning because exposure can impair the sense of smell.
- Forms flammable mixtures with air; combustion can produce toxic sulfur dioxide.
- Can accumulate in poorly ventilated or low-lying spaces, creating severe confined-space hazards.
- In wet service, can contribute to corrosion, hydrogen damage, and sulfide stress cracking in susceptible metals.
- Which of these failure modes and hazards hold for the sense of hydrogen sulfide this model covers, and on what evidence? provenance
Regional variation
Recalled without web access and unsourced; every item is a lead to verify.
- Occupational exposure limits, averaging periods, and ceiling limits differ between jurisdictions and issuing bodies.
- Hazard communication and transport requirements depend on local implementation and the supplied concentration or formulation.
- Which of these regional variation hold for the sense of hydrogen sulfide 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.
- Hydrosulfide ion - HS⁻ is the singly deprotonated ionic species; hydrogen sulfide is neutral H₂S.
- Sulfide ion - S²⁻ is an ionic species with no hydrogen atoms; hydrogen sulfide is a neutral molecular compound.
- Sulfur dioxide - SO₂ contains sulfur and oxygen and has different chemistry and hazards.
- Sour gas - Sour gas is a gas mixture containing hydrogen sulfide; it is not the pure substance.
- Hydrosulfuric acid - This name denotes hydrogen sulfide in aqueous solution, where acid-base speciation matters.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of hydrogen sulfide this model covers, and on what evidence? provenance
What the second pass must settle
- Does an existing Vercy world model already own hydrogen sulfide or the relevant chemical-species concept, requiring this registry entry to link to it?
- Which authoritative sources will establish the substance identifiers and condition-specific physical constants for the completed model?
- Which jurisdictions and use settings must be covered by researched GHS classifications, exposure limits and transport requirements?
- Which aqueous speciation and gas-partition references are valid across the temperature, pH and salinity ranges the model must support?
- Which analytical methods, impurity specifications and compatibility references are required for the intended grades and occurrence types?