sodium sulfate
Enable an AI agent to identify sodium sulfate, assess its hydration and quality, and determine whether a particular material is suitable for a proposed use or transformation.
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.
Researched by: Codex + Grok
Purpose and description
Enable an AI agent to identify sodium sulfate, assess its hydration and quality, and determine whether a particular material is suitable for a proposed use or transformation.
Sodium sulfate is the inorganic salt Na2SO4 (CAS 7757-82-6), occurring as the anhydrous mineral thenardite and the decahydrate mirabilite (Glauber's salt), produced industrially as a by-product of HCl and rayon manufacture and used as a kraft-pulp makeup chemical, a detergent filler, and a glass-batch sulfate source.
It can be Verify or quarantine a labelled sodium sulfate material using identity, phase and assay evidence.; Calculate a required sodium sulfate quantity using the measured assay and a declared hydration basis.; Assess whether a lot meets a specified reagent, drying or industrial formulation requirement.; Plan dissolution or crystallisation using concentration, temperature and applicable phase data.; Select an evidenced drying or reconditioning procedure and require checks before reuse.; Set storage and retesting conditions appropriate to the required hydration and handling state..
Distinguishing features
Require evidence for both sodium and sulfate consistent with Na2SO4; a white appearance or sodium identification alone cannot establish identity.
Use an anion-specific analysis capable of separating sulfate from sulfite and chloride rather than treating similarly named or coloured salts as equivalent.
Distinguish sodium hydrogen sulfate through composition and acidity evidence; pH alone is insufficient to establish Na2SO4 identity.
Determine crystal phase and water content to distinguish anhydrous sodium sulfate from its decahydrate; both forms belong within this proposed scope. [PubChem](https://pubchem.ncbi.nlm.nih.gov/compound/sodium_sulfate)
For mixed solutions, distinguish a measured sulfate concentration from an attributable sodium sulfate quantity; coexisting sodium and sulfate do not uniquely identify the salt originally dissolved.
Scope
+ Identification of Na2SO4 and evidence distinguishing it from other sodium salts or sulfate salts
+ Anhydrous, hydrated, mixed-phase and unresolved hydration states
+ Sodium sulfate content, water content and impurities with explicit reporting bases
+ Solid condition and sodium sulfate behaviour during dissolution, crystallisation and storage
+ Evidence supporting acceptance, reconditioning or rejection for a specified use
- Sodium sulfite, sodium hydrogen sulfate and other chemically distinct salts
- Complete compositions and properties of brines, detergents or other mixtures containing sodium sulfate
- Mining deposits, geological formations and extraction operations
- Design and operation of manufacturing, drying or crystallisation equipment
- Clinical prescribing, food formulation and finished-product approval
- Building deterioration and thermal-storage system performance beyond the sodium sulfate material contribution
Characteristics
- Identity confidence
- label-only | analytically supported | conflicting | unresolved Prevents a supplier name or appearance from being treated as verified chemical identity.
- Hydration and phase assignment
- anhydrous | decahydrate | other identified hydrate | mixed phases | unresolved Determines how mass, water content and phase-dependent behaviour should be interpreted.
- Sodium sulfate assay
- mass % as Na2SO4, explicitly as-received or on a defined dry basis Supports comparable purity assessments and correct quantities despite differing water contents.
- Water content and assignment
- mass % water with method; crystal water, surface moisture and unassigned water distinguished where supported A total water result alone cannot establish a unique hydrate or usable drying condition.
- Impurity profile
- mg/kg or mass % by named impurity, including detection limits and reporting basis Chloride, other salts, insoluble matter or trace contaminants may determine suitability independently of the main assay.
- Particle and handling condition
- powder | granular | crystalline | caked | wet; particle-size distribution in µm where relevant Supports decisions about dispensing, dissolution and whether conditioning is necessary.
- Condition history
- linked temperature, humidity, wetting, drying and container-exposure observations Connects observed hydration or caking to conditions that may have changed the material.
- Dissolved concentration
- g Na2SO4/kg solution or mol/kg water, with temperature and attribution basis Avoids confusing solution concentration, solid hydrate mass and salt-equivalent quantity.
- Use-specific qualification
- linked intended use, specification revision, evidence and acceptance decision Chemical identity alone does not establish fitness for drying, formulation or another application.
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 · 18 findings · 38 questions.
Salt identity and boundaries Establish whether the material is sodium sulfate and what portion of a sample this identity describes.
Similar salt names and nonspecific observations can produce a plausible but incorrect identification.
Chemical discrimination
Resolve the sodium sulfate identity against neighbouring salts.
Supported Na2SO4 identity
Record the analytical and documentary evidence for sodium sulfate, including contradictory results.
- What evidence establishes sodium and sulfate in a composition consistent with Na2SO4? definition
- Which analyses distinguish this material from sodium sulfite, sodium hydrogen sulfate and sodium chloride? measurement
- Does the identification describe the whole material or only one component? boundary
Form and entry mapping
Connect labels and hydrate descriptions to the single registry entry.
Label-to-material mapping
Preserve the supplier's identity and form claims while distinguishing them from verified observations.
- Does the label identify anhydrous sodium sulfate, a hydrate or an unspecified form? provenance
- Are the stated name, formula and substance identifier consistent with the claimed hydration state? definition
- Does an existing catalogue model already own this concept and require a link instead of another publication? boundary
Hydration and phase state Represent the water-bearing and crystalline state of sodium sulfate under observed conditions.
Hydration affects salt-equivalent mass and behaviour; it cannot safely be inferred from the substance name.
Phase identification
Separate crystal-phase assignments from bulk water measurements.
Resolved hydrate composition
Record evidence for anhydrous, hydrated or mixed phases without forcing an uncertain sample into a single form.
- Which crystalline phases are supported by diffraction, spectroscopy or another validated method? measurement
- How much measured water is assigned to crystal water rather than surface moisture or retained solution? measurement
- Could sample preparation have changed the hydration state before measurement? provenance
Phase-change conditions
Connect phase observations to environmental and treatment history.
Hydration-state persistence
Record the conditions under which the assigned phase remains supported and when reassessment is needed.
- What temperature, humidity and contact with liquid water preceded the current observation? provenance
- Which applicable phase data constrain the expected state at the proposed storage or process conditions? boundary
- What exposure or treatment requires a new phase or water-content measurement? action
Assay and salt equivalent Determine how much sodium sulfate is present and whether associated material is acceptable.
Hydrate water and impurities make gross sample mass an unreliable substitute for Na2SO4 quantity.
Quantity basis
Make assays and requested quantities comparable across hydration states.
Traceable salt equivalent
Express usable sodium sulfate content with its assay method, denominator and uncertainty.
- Is the assay expressed as Na2SO4 on an as-received basis, a defined dry basis or a named hydrate basis? definition
- What measured assay and uncertainty apply to the material being dispensed? measurement
- What sample mass supplies the requested Na2SO4 amount after applying the supported assay basis? action
Impurity selectivity
Distinguish sodium sulfate from contaminants that alter acceptance or bias its measurement.
Use-relevant contaminants
Record named impurity results and whether the assay distinguishes sodium sulfate from other sulfate-bearing material.
- Which chloride, other-ion, insoluble-matter or trace-contaminant limits apply to the intended use? boundary
- Could other sulfate salts inflate a sulfate-based sodium sulfate assay? measurement
- Which lot-specific results and detection limits demonstrate compliance with those limits? provenance
Dissolution and crystallisation Support decisions involving transfer between solid sodium sulfate and aqueous solution.
Concentration, temperature and solid-phase identity must be considered together when assessing dissolution or precipitation.
Solution accounting
Track sodium sulfate equivalents in solution without implying identifiable dissolved salt molecules.
Defined solution concentration
Record concentration, water contribution and attribution evidence for dissolved sodium sulfate.
- What is the concentration, its denominator and the measurement temperature? measurement
- Has water introduced by a hydrated solid been included in the solution mass balance? measurement
- In a mixed brine, what evidence supports attributing an amount to sodium sulfate rather than reporting sodium and sulfate separately? boundary
Solid-liquid transition
Assess dissolution and crystallisation against data applicable to the actual composition.
Phase-specific saturation
Connect saturation assessments and recovered crystals to the relevant sodium sulfate phase.
- Which solubility data apply to the temperature, solvent composition and candidate solid phase? provenance
- Is the material fully dissolved, in equilibrium with solids or in an unresolved transient state? measurement
- What phase and mother-liquor checks are required before recovered crystals can be assigned a composition? action
Fitness and material conditioning Translate sodium sulfate condition into a justified use, treatment or rejection decision.
The required hydration, purity and particle condition depend on the proposed role, so identity alone cannot authorize use.
Role-specific acceptance
Relate the lot's measured properties to a declared application.
Qualified material role
Record whether the material meets the requirements of its proposed role and where qualification remains incomplete.
- Is the proposed role a sulfate feedstock, formulation ingredient, drying agent or another explicitly defined use? definition
- Which hydration, impurity and particle-condition requirements determine acceptance for that role? boundary
- If proposed for drying, what evidence establishes adequate water-removal performance in the actual solvent and conditions? measurement
Storage and reconditioning
Control changes that could invalidate the required sodium sulfate condition.
Condition-preserving actions
Link storage, drying or reuse decisions to the target hydration state and contamination history.
- What container and environmental conditions are supported for maintaining the required hydration and flow condition? action
- Has prior use introduced solvents or contaminants that prevent treating this material as fresh sodium sulfate? provenance
- What validated conditioning procedure and post-treatment checks are required before release or reuse? 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.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- anhydrous sodium sulfate (thenardite)
- sodium sulfate decahydrate (mirabilite, Glauber's salt)
- sodium sulfate heptahydrate
- natural mineral thenardite
- natural mineral mirabilite
- technical/industrial grade (detergent, glass, kraft pulp)
- pharmaceutical/analytical grade (USP/Ph. Eur. anhydrous or decahydrate)
- food-grade additive (E 514)
- Which of these kinds and varieties hold for the sense of sodium sulfate this model covers, and on what evidence? provenance
Identifiers and schemes
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- CAS Registry Number - 7757-82-6 (anhydrous); 7727-73-3 (decahydrate) - Anhydrous and decahydrate have distinct CAS numbers; heptahydrate is 15225-75-4.
- EC / EINECS - 231-820-9 - ECHA substance identity for sodium sulphate.
- PubChem CID - 24436 - Compound record for Na2SO4.
- InChIKey - PMZURENOXWZQFD-UHFFFAOYSA-L - Canonical key for the anhydrous salt.
- Wikidata - Q211737 - Item for sodium sulfate; mineral thenardite is Q407806, mirabilite Q422201.
- UNII - 36KCS0R750 (anhydrous); 0YPR65R21J (decahydrate) - FDA Unique Ingredient Identifiers used in drug listings.
- EU food additive - E 514 - Sodium sulphates (E 514(i) sodium sulphate, E 514(ii) sodium hydrogen sulphate in some listings).
- HS / CN code - 2833.11 (disodium sulphate) - Harmonized System heading for disodium sulfate in trade statistics.
- Which of these identifiers and schemes hold for the sense of sodium sulfate this model covers, and on what evidence? provenance
Standards and regulation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- USP / NF monograph Sodium Sulfate (United States Pharmacopeial Convention) for pharmaceutical anhydrous and decahydrate grades
- Ph. Eur. Sodium sulfate, anhydrous and Sodium sulfate decahydrate (European Directorate for the Quality of Medicines)
- FCC / Codex specifications for food-grade sodium sulfate (Food Chemicals Codex; JECFA/Codex Alimentarius for E 514)
- Regulation (EC) No 1333/2008 and Commission Regulation (EU) No 231/2012 specifications for E 514 (European Commission / EFSA re-evaluation)
- REACH registration under EC 231-820-9 (ECHA); not classified as hazardous under CLP for the pure salt in the typical infocard listing
- OSHA / NIOSH workplace exposure practice treats it as a nuisance/particulate dust rather than a listed toxic air contaminant (US DOL / CDC NIOSH)
- ISTA / ASTM soil and concrete sulfate tests (e.g. ASTM C1580, related EN 206 sulfate-class rules) govern sulfate attack on concrete when sodium sulfate is the exposure salt, not a product spec for the chemical itself
- Which of these standards and regulation hold for the sense of sodium sulfate this model covers, and on what evidence? provenance
Real-world use
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Kraft pulp mill makeup chemical: supplies sodium and sulfate ions to the recovery cycle (salt cake)
- Powder detergent filler and processing aid, historically a major consumer of natural and by-product salt cake
- Glass batch sulfate: refining/fining agent and source of SO3 in soda-lime glass
- Textile processing: Glauber's salt as a levelling/exhaustion salt in cotton dyeing with reactive and vat dyes
- Laboratory drying of organic extracts (anhydrous Na2SO4) where a milder, cheaper desiccant than MgSO4 is acceptable
- Osmotic laxative in oral bowel-prep and veterinary products (decahydrate / pharmaceutical grade)
- Thermal energy storage: Glauber's salt phase-change material around 32 °C, limited by incongruent melting and phase segregation
- Construction/geotech hazard rather than a product: mirabilite/thenardite cycling causes salt weathering of stone and sulfate attack of concrete
- Which of these real-world use hold for the sense of sodium sulfate this model covers, and on what evidence? provenance
Typical measurements
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- assay (Na2SO4, dry basis) - 99.0-99.9 (technical ~98-99.5; reagent/Ph.Eur. ≥99.0) - % w/w
- water of crystallization / loss on drying - anhydrous <0.5; decahydrate ~55-56 (theoretical 55.9) - % w/w H2O
- melting point (anhydrous) - 884 - °C
- decahydrate incongruent melting / transition - 32.4 (Na2SO4·10H2O → anhydrous + solution) - °C
- density (anhydrous, 20 °C) - 2.66-2.70 - g·cm−3
- aqueous solubility (anhydrous, 20 °C) - about 19-20 (rises sharply toward 32 °C then falls for the anhydrous form) - g/100 g water
- chloride and iron as impurities (industrial/Ph.Eur.) - Cl typically ≤0.05-0.2; Fe often ≤10-50 - % w/w Cl; mg·kg−1 Fe
- Which of these typical measurements hold for the sense of sodium sulfate this model covers, and on what evidence? provenance
Failure modes and hazards
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Hydration cycling (thenardite ↔ mirabilite) generates crystallization pressure that spalls stone, brick, and concrete (salt weathering).
- Sulfate attack of Portland cement: ettringite/gypsum formation and expansion in soils or groundwater rich in sodium sulfate.
- Incongruent melting of Glauber's salt in heat-storage packs: anhydrous crystals settle, capacity is lost, packs leak or stratify.
- Caking and hydrate uptake on storage of the anhydrous salt in humid air; the decahydrate effloresces in dry air.
- Dust irritation of eyes and respiratory tract; large oral doses cause osmotic diarrhea and electrolyte disturbance (intended as a laxative, hazardous in overdose or in infants).
- Not a strong oxidizer and not classified like sodium chlorate; the main chemical confusion hazard is mis-identifying it as sodium sulfite (reductant) or sodium bisulfate (acid salt) in a process charge.
- Which of these failure modes and hazards hold for the sense of sodium sulfate this model covers, and on what evidence? provenance
Regional variation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- English 'salt cake' and German 'Glaubersalz' remain trade names; mineral names thenardite/mirabilite dominate geology, while detergent and pulp industries still say salt cake.
- Natural production is concentrated in evaporite lakes (e.g. Spain, Canada, US Great Basin, China, former USSR); Western Europe historically relied more on Mannheim/HCl and rayon by-product sulfate.
- EU food law lists E 514; US food use is as a miscellaneous/processing salt rather than a prominent labelled additive.
- Spelling: sulphate (IUPAC/UK/EU regulatory texts) vs sulfate (US, IUPAC alternative, CAS indexing).
- Which of these regional variation hold for the sense of sodium sulfate this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- sodium sulfite (Na2SO3) - Sulfite is a reductant (deoxygenates, bleaches, iodometric titre); sulfate is redox-inert under those tests. IR/Raman: sulfite vs sulfate stretching; wet test: acidified sulfite evolves SO2, sulfate does not.
- sodium bisulfate / sodium hydrogen sulfate (NaHSO4) - Acid salt: aqueous pH strongly acidic (~1 for concentrated solutions) vs near-neutral Na2SO4; melts/decomposes as an acid flux, not a high-melting neutral sulfate.
- sodium bisulfite / metabisulfite (NaHSO3 / Na2S2O5) - Preservative/reductant with SO2 odour on acidification; sulfate gives no SO2 and no iodine consumption.
- magnesium sulfate (Epsom salt, MgSO4·7H2O) - Both are bitter saline hydrates used as laxatives; flame test or AAS/ICP: Na yellow vs Mg; Epsom heptahydrate is the common pharmacy hydrate, Glauber's salt is the decahydrate of sodium.
- sodium carbonate (soda ash) and sodium chloride - Carbonate effervesces with acid and is alkaline; chloride gives AgCl with AgNO3 that is insoluble in nitric acid. Sulfate gives a BaSO4 precipitate insoluble in acid.
- calcium sulfate (gypsum/anhydrite) - Much lower solubility; does not supply soluble Na+; XRD and solubility separate thenardite/mirabilite from gypsum in evaporites and concrete.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of sodium sulfate this model covers, and on what evidence? provenance
Sources
- Sodium sulfate (Compound) - Formula Na2SO4, CAS 7757-82-6, InChIKey, hydrates, melting point, density, solubility, uses, and GHS/hazard notes from a curated NIH compound record.
- Sodium sulfate - Mineral names thenardite and mirabilite, Glauber's salt, industrial production routes, kraft-pulp/detergent/glass uses, hydrate phases, and distinction from sodium sulfite and sodium bisulfate.
- Sodium sulphate - Substance Infocard - EC 231-820-9, REACH registration, and EU regulatory identity for sodium sulphate.
- Re-evaluation of sodium sulphate (E 514) as a food additive - EU food-additive identity E 514, specifications context, and authorised use as an acidity regulator/carrier rather than a nutrient salt.
What the second pass must settle
- Does an existing Vercy world model already cover sodium sulfate, and what registry boundary has been established for its hydrate forms?
- Which authoritative phase-equilibrium and kinetic sources should govern hydrate assignments under the intended temperature, humidity and solution conditions?
- Which analytical methods can reliably distinguish crystal water, surface moisture and retained mother liquor in the expected samples?
- Which application-specific specifications and impurity limits must be supported, and how should conflicting grade claims be resolved?
- What evidence is available for drying performance, reconditioning limits and reuse acceptance under the actual solvents and contamination histories?