calcium oxide
Enable an agent to recognise calcium oxide, assess its composition and reactivity, and determine whether a particular material is suitable for an intended use or handling action.
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 recognise calcium oxide, assess its composition and reactivity, and determine whether a particular material is suitable for an intended use or handling action.
Calcium oxide (CaO), commonly called quicklime, is a basic inorganic oxide composed of calcium and oxygen that forms a crystalline solid under ambient conditions and reacts exothermically with water to produce calcium hydroxide.
It can be Resolve whether an item labelled lime is calcium oxide, another calcium compound or a mixture requiring further identification.; Compare a lot's measured composition and reactivity against an intended-use specification.; Determine whether storage exposure warrants retesting for hydration or carbonation.; Estimate reaction quantities from verified reactive CaO content while recording assumptions and uncertainty.; Select handling and storage requirements from the material's current safety documentation and planned operation.; Trace a suitability decision to sampling records, analytical methods and supplier evidence..
Distinguishing features
The chemical identity is CaO; a material described only as lime needs evidence distinguishing oxide, hydroxide, carbonate and mixtures.
Contact with water converts CaO to calcium hydroxide and releases heat; the extent of conversion distinguishes fresh quicklime from partly or fully slaked material.
Carbonation produces calcium carbonate, so a weathered sample may retain the quicklime label while containing substantially less unreacted CaO.
Total calcium or a result reported as CaO equivalent does not by itself establish that calcium oxide is the calcium-bearing phase.
Commercial quicklime can contain other oxides and mineral phases; its name alone does not establish pure CaO or a particular grade.
Scope
+ Chemical identity and distinction between calcium oxide and commercial quicklime compositions
+ CaO content, impurities, grade and evidence of suitability for a stated use
+ Physical form, phase, particle size and condition-dependent properties
+ Hydration, carbonation and the resulting loss of unreacted calcium oxide
+ Reactivity, storage condition, exposure hazards and applicable substance classifications
- Calcium hydroxide as a separately supplied substance
- Calcium carbonate, limestone and their geological deposits
- Complete formulations containing calcium oxide, including cement and mixed treatment products
- Lime kilns, calcination plants and their operating models
- Slaking equipment and complete industrial slaking procedures
- Biological calcium metabolism and dietary calcium requirements
Characteristics
- Chemical and registry identity
- CaO; vr.tr.calcium-oxide; verified CAS, EC and PubChem identifiers Connects the substance to reference records while preventing ambiguous lime names from determining identity.
- Unreacted calcium oxide content
- Mass percent, with analytical method and reporting basis Distinguishes actual CaO from total calcium, CaO-equivalent reporting and transformed calcium phases.
- Hydroxide and carbonate content
- Mass percent Ca(OH)2 and CaCO3, with method and sampling date Indicates hydration or carbonation and helps explain changes in performance.
- Impurity composition
- Mass percent or mg/kg of identified constituents, including MgO and application-relevant contaminants Determines whether commercial quicklime meets the composition requirements of its intended use.
- Grade and intended-use specification
- Named specification, edition, intended application and supporting certificate Prevents an industrial grade from being treated as suitable for every use.
- Physical form and size distribution
- Powder, granules or lumps; particle sizes in µm or mm with distribution and method Affects dust generation, handling and the rate of reaction with water.
- Phase and thermal properties
- Observed phase; transition temperatures in K or °C with pressure, purity and source Supports condition-specific identification without treating reference constants as universal sample properties.
- Slaking reactivity
- Temperature rise in °C and elapsed time in s or min under a named test protocol Measures how rapidly a particular quicklime material reacts with water.
- Storage and weathering state
- Documented moisture and air exposure, packaging integrity, caking and analytical evidence of transformation Supports decisions to retain, retest or reject material after storage.
- Hazard classification and exposure criteria
- Current SDS and applicable classification; exposure limits in mg/m³ with jurisdiction, aerosol fraction and averaging period Connects dust exposure and water-reactivity decisions to the actual supplied material and governing requirements.
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 · 29 questions.
CaO identity and boundaries Establishes when a record represents calcium oxide and when it represents another lime substance or a mixed product.
Lime terminology and oxide-equivalent analyses can obscure the chemical species actually present.
Chemical identity
Connects the CaO identity to authoritative identifiers and identification evidence.
Verified CaO identity
Record evidence establishing calcium oxide identity independently of trade names.
- Which authoritative records establish the CAS number, EC number and PubChem CID for CaO? provenance
- What evidence shows that the material contains calcium oxide rather than merely calcium reported as CaO equivalent? definition
Quicklime product boundary
Separates the chemical substance from commercial quicklime grades and neighbouring calcium compounds.
Lime name resolution
Record what a supplied lime name denotes and which additional constituents require product-level treatment.
- Does the supplied name denote high-calcium quicklime, a magnesium-bearing quicklime, hydrated lime or another material? boundary
- Which constituents or additives require a linked mixture or product model beyond this CaO model? boundary
Composition and grade Captures how much usable calcium oxide is present and what composition constraints govern its application.
Total calcium, reactive CaO and application suitability are different judgments requiring distinct evidence.
CaO assay basis
Makes composition results interpretable across laboratories and specifications.
Measured CaO fraction
Record assay definitions, methods and reporting bases before interpreting a percentage as usable CaO.
- Does the reported value measure total calcium as CaO, free CaO or available lime under a specified test? measurement
- Is the result reported as received, on a dry basis or on another basis, and what sampling uncertainty applies? measurement
Impurities and use qualification
Connects impurity measurements and grade claims to the proposed use.
Application-specific acceptance
Record the requirements that make a particular quicklime lot acceptable for an application.
- What limits apply to MgO, residual carbonate, insoluble matter and trace contaminants for the intended use? measurement
- Which specification and lot-specific evidence support accepting or rejecting this material for that use? action
Physical form and reactivity Describes physical properties that affect recognition, handling and reaction behaviour.
CaO composition alone does not predict the dustiness or slaking behaviour of a particular quicklime lot.
Particle and phase properties
Records particle form and condition-dependent reference or sample measurements.
Conditioned physical properties
Keep particle measurements, density definitions and thermal properties tied to their measurement conditions.
- What particle-size distribution and fines fraction describe this powder, granule or lump material? measurement
- Which density and melting or boiling-point values are supported, and under what phase, pressure and purity conditions? provenance
Slaking performance
Captures measured reaction behaviour under a defined water-contact test.
Test-defined slaking reactivity
Record reaction rate and heat-development evidence without assuming all CaO lots behave alike.
- What temperature-time curve or specified reactivity endpoint was measured using which slaking test? measurement
- What water ratio, initial temperature, particle preparation and agitation conditions are required to interpret that result? measurement
Hydration, carbonation and storage Tracks chemical transformation during exposure to water, moisture and carbon dioxide.
A container can retain its calcium oxide label after its contents have partly transformed into hydroxide or carbonate.
Transformation state
Distinguishes remaining CaO from its hydration and carbonation products.
Remaining oxide and products
Record evidence of CaO consumption and the resulting calcium-bearing phases.
- What measurements distinguish remaining CaO from Ca(OH)2 and CaCO3 in the sampled material? measurement
- At what measured composition should this item be represented as a transformed material or mixture rather than an acceptable quicklime lot? boundary
Storage exposure history
Connects environmental exposure and packaging condition to decisions about continued use.
Weathering and retest decision
Record exposure evidence and criteria for retesting material whose condition may have changed.
- What moisture ingress, air exposure, packaging damage or storage duration is documented for this lot? provenance
- Which changes in assay, slaking performance or physical condition trigger retesting, segregation or rejection? action
Exposure and handling decisions Connects calcium oxide's dust and water-contact behaviour to evidence-based operational constraints.
Handling decisions must account for both particulate exposure and heat released during hydration.
Dust and contact exposure
Records classifications and exposure criteria applicable to the supplied material.
Applicable exposure evidence
Tie exposure judgments to the current SDS, jurisdiction and relevant dust fraction.
- Which current hazard classifications and exposure routes are documented for this calcium oxide grade? provenance
- Which occupational exposure limits apply, with what aerosol fraction, averaging period, units and jurisdiction? measurement
Water contact and compatibility
Distinguishes controlled hydration from unintended water contact and other incompatible conditions.
Operation-specific handling constraints
Record the approved controls for the planned operation and its credible exposure conditions.
- Does the planned action involve dry transfer, deliberate slaking, cleanup or another operation with different water-contact constraints? action
- What handling, segregation and emergency-response requirements are established by the applicable SDS and operating procedure? 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 standard editions, jurisdiction-specific GHS classifications and occupational exposure limits before regulatory use.
- Burning categories describe commercial processing and reactivity, not distinct chemical compounds; product purity, available lime and slaking behavior require measurement.
- Which of these check these first hold for the sense of calcium oxide this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- High-purity calcium oxide
- Commercial high-calcium quicklime
- Soft-burned quicklime
- Hard-burned quicklime
- Dead-burned quicklime
- Which of these kinds and varieties hold for the sense of calcium oxide this model covers, and on what evidence? provenance
Identifiers and schemes
Recalled without web access and unsourced; every item is a lead to verify.
- Chemical formula - CaO - Identifies the compound; commercial quicklime may contain other oxides and residual carbonate.
- CAS Registry Number - 1305-78-8 - Calcium oxide.
- EC number - 215-138-9 - European substance inventory identifier.
- PubChem CID - 14778 - Calcium oxide compound record.
- Which of these identifiers and schemes hold for the sense of calcium oxide this model covers, and on what evidence? provenance
Standards and regulation
Recalled without web access and unsourced; every item is a lead to verify.
- CEN EN 459-1 specifies definitions, specifications and conformity criteria for building lime, including quicklime products.
- ASTM International ASTM C5 specifies quicklime for structural purposes.
- ASTM International ASTM C110 provides physical testing methods for quicklime, hydrated lime and limestone.
- ASTM International ASTM C25 provides chemical analysis methods for limestone, quicklime and hydrated lime.
- Which of these standards and regulation hold for the sense of calcium oxide this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Flux in iron and steel production, helping transfer impurities into slag.
- Manufacture of hydrated lime by controlled reaction with water.
- Soil stabilization and drying in civil engineering.
- Neutralization of acidic streams and treatment of water or wastewater.
- Regeneration of sodium hydroxide from sodium carbonate in the kraft pulping recovery cycle.
- Which of these real-world use hold for the sense of calcium oxide 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 - 56.08 - g/mol
- Density of crystalline calcium oxide near room temperature - approximately 3.34 - g/cm³
- Melting point - approximately 2572 - °C
- Standard reaction enthalpy for CaO(s) + H2O(l) → Ca(OH)2(s) - approximately -65 - kJ/mol
- Which of these typical measurements hold for the sense of calcium oxide 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.
- Hydration releases substantial heat and can cause overheating, boiling and splashing when water contacts bulk quicklime.
- Contact with moisture produces strongly alkaline calcium hydroxide; exposure can injure skin and severely damage eyes.
- Airborne dust irritates the respiratory tract.
- Exposure to atmospheric moisture and carbon dioxide converts the material toward hydroxide and carbonate, reducing available calcium oxide.
- Incomplete or delayed hydration of coarse or heavily burned particles can cause expansion and damage in construction materials.
- Which of these failure modes and hazards hold for the sense of calcium oxide this model covers, and on what evidence? provenance
Regional variation
Recalled without web access and unsourced; every item is a lead to verify.
- Construction lime specifications use different classification systems, including EN standards in Europe and ASTM standards in North America.
- Occupational exposure limits and legally required hazard labels depend on jurisdiction and require local verification.
- Which of these regional variation hold for the sense of calcium oxide 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.
- Calcium hydroxide - Ca(OH)2 is hydrated or slaked lime; calcium oxide is CaO before hydration.
- Calcium carbonate - CaCO3 contains carbonate and releases carbon dioxide during calcination to produce calcium oxide.
- Dolomitic quicklime - Contains substantial magnesium oxide alongside calcium oxide and is a commercial mixed material.
- Lime - An umbrella term whose meaning may include quicklime, hydrated lime or other lime products; calcium oxide specifies one compound.
- Cement - A formulated binder containing reactive mineral phases; its reported CaO content does not imply that the calcium occurs as free calcium oxide.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of calcium oxide this model covers, and on what evidence? provenance
What the second pass must settle
- Which existing Vercy world model, if any, already owns calcium oxide or quicklime and should receive this registry link?
- Which authoritative sources confirm the substance identifiers and condition-specific physical constants, especially reported boiling-point values?
- How do the relevant standards define free CaO, available lime and quicklime grades, and which results can legitimately be compared?
- Which current jurisdiction-specific hazard classifications and occupational exposure limits apply to the intended users and supplied grades?
- What application-specific evidence establishes acceptable hydration, carbonation and storage-related deterioration thresholds?