Calcium peroxide (1305-79-9) Physical and Chemical Properties
Calcium peroxide
Inorganic solid peroxide used as a controlled-release oxygen source and oxidizing agent, commonly supplied as a granular or powdered material for industrial processing, remediation and food-processing formulations.
| CAS Number | 1305-79-9 |
| Family | Metal peroxides (inorganic oxidizers) |
| Typical Form | Powder or crystalline solid |
| Common Grades | EP, FCC |
Calcium peroxide is an inorganic metal peroxide in which calcium cations are ionically associated with the peroxide dianion; its empirical composition is \(\ce{CaO2}\). Structurally it is best described as an ionic lattice containing \(\ce{Ca^2+}\) and the peroxide moiety \(\ce{O2^2-}\). The peroxide dianion confers strong oxidizing character and a labile O–O bond that is susceptible to protonation and reductive cleavage; in contact with acids or catalytic surfaces the peroxide moiety is converted to hydrogen peroxide \(\ce{H2O2}\) and/or elemental oxygen \(\ce{O2}\), while reaction with water slowly yields calcium hydroxide \(\ce{Ca(OH)2}\) and oxygen. The material typically appears as a white to yellowish granular solid with low molecular complexity and limited molecular flexibility.
From a physico‑chemical perspective CaO2 behaves as a sparingly soluble, strongly basic, inorganic oxidizer. Its aqueous behavior is dominated by limited dissolution and surface hydrolysis; dissolved peroxide species and surface-generated \(\ce{H2O2}\) determine redox activity, biocidal effects, and oxygen release kinetics used in environmental applications. The compound is non‑volatile, denser than water in solid form, hygroscopic to an extent, and thermally unstable above moderate temperatures where exothermic decomposition becomes significant. Industrially it is employed as a controlled oxygen source, oxidizing agent, and flour treatment/dough‑conditioning additive, and has niche uses in remediation, wastewater treatment, and metal‑leaching processes.
Common commercial grades reported for this substance include: EP, FCC.
Basic Physical Properties
Density
Reported solid‑phase densities include "2.92 at 77 °F (USCG, 1999) - Denser than water; will sink" and "2.9 g/cu cm". These values indicate a bulk solid density approximately \(\mathrm{2.9\ g\ cm^{-3}}\), consistent with an ionic crystalline peroxide.
Melting or Decomposition Point
Calcium peroxide does not exhibit a conventional melting point before decomposition; an onset of thermal decomposition is reported as "Decomp at 200 °C" and "Decomposes /at/ approximately 200 °C ...". Thermal decomposition is exothermic and can be accelerated by heat, shock, or catalytic impurities.
Solubility in Water
Solubility is described as "Slightly soluble in water." The solid undergoes slow hydrolytic decomposition in aqueous media to produce \(\ce{Ca(OH)2}\) and oxygen; the commercial product is often formulated as granules for controlled oxygen release. It is also reported as "Soluble in acids with formation of hydrogen peroxide," reflecting acid‑promoted protonation of the peroxide dianion.
Solution pH (Qualitative Behavior)
No single experimental pH value is provided for saturated solutions. Qualitatively, aqueous interaction produces basic conditions due to formation of \(\ce{Ca(OH)2}\); hence, solutions or slurries tend to be alkaline. In acidic media the peroxide moiety is converted to \(\ce{H2O2}\), temporarily lowering solution pH while generating oxidizing species.
Chemical Properties
Acid–Base Behavior
Calcium peroxide is a basic salt: reaction with water and protic media yields hydroxide and releases oxygen species. In acids it reacts to form hydrogen peroxide according to stoichiometric protonation of the peroxide dianion. The material is therefore both a source of basicity (via \(\ce{Ca^{2+}}\) → \(\ce{Ca(OH)2}\)) and a source of oxidizing peroxide species under acidic or catalytic conditions.
Reactivity and Stability
- Stability: "Stable under recommended storage conditions." However, it "Decomposes in moist air."
- Thermal decomposition: exothermic decomposition occurs near 200 °C; the heat of decomposition is reported as \(\mathrm{-135\ Btu\ lb^{-1} = -75\ cal\ g^{-1} = -3.1\times10^{5}\ J\ kg^{-1}}\).
- Reactivity hazards: classified as a strong oxidizer; may intensify fire and accelerate combustion of organic materials. It is "Explosive" and a "Strong Oxidizing Agent" in certain mixtures and can decompose violently under heat, shock, or in the presence of catalysts or contaminants.
- Incompatibilities: organic materials, finely divided combustibles, reducing agents, powdered metals, sulfides, fluorine, ethanol and other reactive organics. Contact with polysulfide polymers has been reported to cause ignition.
- Hydrolytic behavior: reacts slowly with water to form \(\ce{Ca(OH)2}\) and oxygen; moisture and heavy‑metal contaminants accelerate decomposition to lime and oxygen.
Collectively these characteristics require control of heat, exclusion of combustible contaminants, and dry storage to minimize decomposition and fire risk.
Molecular and Ionic Parameters
Formula and Molecular Weight
- Molecular formula: \(\ce{CaO2}\).
- Molecular weight: 72.08 (reported).
- Exact/monoisotopic mass: 71.9524201 (reported).
Additional computed descriptors: Topological polar surface area (TPSA) 46.1; heavy atom count 3; formal charge 0; hydrogen bond donor count 0; hydrogen bond acceptor count 2; rotatable bond count 0.
Constituent Ions
The solid comprises calcium cations and peroxide dianions; the principal ionic constituents can be represented as \(\ce{Ca^2+}\) and the peroxide ion \(\ce{O2^2-}\). The peroxide dianion’s O–O bond is the redox‑active center responsible for oxygen and \(\ce{H2O2}\) generation in water or acid.
Identifiers and Synonyms
Registry Numbers and Codes
- CAS number: 1305-79-9
- Additional registry and code identifiers reported: deprecated CAS values (e.g., 12049-69-3; 55396-25-3; 61976-87-2) and alternate CAS 78403-22-2 appear in historical records.
- European Community (EC) numbers: 215-139-4 and 684-873-9.
- UN number (transport): 1457 (Calcium peroxide).
- Other identifiers noted: ChEBI CHEBI:48233; DSSTox DTXSID4050489; HMDB HMDB0303747.
- Chemical structure identifiers: InChI:
InChI=1S/Ca.O2/c;1-2/q+2;-2; InChIKey:LHJQIRIGXXHNLA-UHFFFAOYSA-N; SMILES:[O-][O-].[Ca+2].
(When using structural identifiers in informatics workflows, present the SMILES and InChI exactly as shown above.)
Synonyms and Common Names
Common synonyms and alternative names reported include (selection): calcium peroxide; calcium dioxide; Calper; Calper G; Calperoxide notations such as Ca(O2) and CaO2; peroxidocalcium; calciumperoxid; cyc‑CaO2; UN1457; and descriptive names used in supply listings (e.g., "Calcium peroxide [UN1457] [Oxidizer]"). The substance is also referenced in food‑additive contexts as "CALCIUM PEROXIDE."
Industrial and Commercial Applications
Functional Roles and Use Sectors
Calcium peroxide is used industrially as a slow‑release oxygen source and oxidizing agent. Key functional roles include: - Flour treatment and dough conditioning (food additive applications as an oxidizing/flour‑treatment agent). - Controlled oxygen release for environmental remediation (soil and sediment oxygenation) and wastewater treatment, including dechlorination and sludge deodorization. - Seed disinfectant and agricultural seed coatings to supply oxygen in flooded or anoxic soils. - Additive in metal leaching (gold recovery) to improve cyanidation kinetics and reduce cyanide consumption. - Oxidizing agent and bleaching aid in certain chemical and polymer processing applications; a stabilizer/curing accelerator in some rubber formulations. - Occasional use in dentifrices and oral hygiene formulations as a peroxide source.
Typical Application Examples
Representative application examples include: - Granulated \(\ce{CaO2}\) used to oxygenate lake sediments or contaminated soils, releasing oxygen over months. - Formulated peroxides applied in gold leaching operations to enhance oxidation of refractory ores. - Low‑level use as a flour improver/dough conditioner in regulated food applications (use levels are tightly controlled by food authorities). - Use as a seed dressing or compost amendment where controlled oxygen release is beneficial for germination or microbial activity.
If detailed application parameters are required for process design (particle size, release kinetics, grade selection), consult product specifications and process‑level data from suppliers.
Safety and Handling Overview
Health and Environmental Hazards
- Hazard classification: strong oxidizer; reported GHS hazard statements include H272: "May intensify fire; oxidizer," H315: "Causes skin irritation," H319: "Causes serious eye irritation," and H335: "May cause respiratory irritation." Some notifications also list acute oral toxicity and severe skin/eye damage categories depending on formulation and impurities.
- Acute effects: inhalation of dust can irritate nose and throat and may cause respiratory irritation or pulmonary effects at higher exposures; contact with skin and eyes can cause severe irritation or burns; ingestion may irritate the gastrointestinal tract.
- Environmental behavior: when used for oxygenation, granules slowly release oxygen; uncontrolled releases of oxidizing solids into the environment can present fire/explosion hazards if mixed with combustibles. Runoff from firefighting or dilution water may cause environmental contamination.
- First aid: remove affected persons from exposure, flush eyes/skin with water for extended periods if contact occurs, and seek medical attention for significant exposures. For inhalation, move to fresh air and obtain medical assistance if symptoms persist.
For detailed hazard, transport and regulatory information, users should refer to the product‑specific Safety Data Sheet (SDS) and local legislation.
Storage and Handling Considerations
- Storage: keep tightly closed in a dry, well‑ventilated place; store away from moisture, heat sources, and incompatible materials (organics, reducing agents, metals). Keep away from combustible materials.
- Handling: avoid dust formation; use local exhaust ventilation where dusts may be generated; implement grounding/bonding protocols when transferring powders to reduce electrostatic ignition risk. Use non‑combustible tools and avoid contamination with organic residues or reducing substances.
- Fire and spill response: oxidizing solids can intensify fires; large incidents may require flooding with water from a safe distance. For small dry spills, sweep or shovel into dry, clean containers; prevent material from entering drains. Do not use combustible absorbents.
- Personal protective equipment: use appropriate respirators for dusts (e.g., N100/P3 for particulate backup to engineering controls), chemical‑resistant gloves, eye/face protection, and impervious clothing when handling bulk material.
- Disposal: dispose of in accordance with local regulations; unused or contaminated material may require treatment by licensed hazardous‑waste contractors. Incineration of peroxide materials requires specialized equipment and controls.
This overview summarizes class‑level safety and handling principles; site‑specific risk assessments and SDS guidance should be followed for operational controls and emergency procedures.
