Calcium oxide

Source of the photo
Author of the description
Berkl Zsófia





Chemical name

Calcium oxide


Lime, Quicklime, Burnt lime, Calcia, Calcium monoxide, Calxyl, Hexocalex, Hexocalex 6-9, Heavy calcium oxide, etc. [1]

IUPAC name

Calcium oxide or oxocalcium


1305-78-8 [2]

REACH registration number



215-138-9 [3]

Molecular formula


Substance group/chemical family

inorganic [3]


Physical state





solid [4]

odourless [5]

cubric crystals, granulated powder or hygroscopic lumps [5]

white, greyish-white, greyish-yellow, brownish-yellow or colorless [5]


Relevant identified uses

Used in construction applications e.g. brick, mortar, stucco production and ground consolidation. [7]

Also used in many other sectors of the industry: bauxite processing, kraft paper pulp production, treatment of sewage and trade waste, treatment of stack gases, water purification and softening, manufacture of glass, paper, drilling fluids, lubricants, chlorinated lime, sodium carbonate (Solvay process), calcium slats, etc. In the industry usually appears as dehydrating agent, absorber, and buffer. [7]

In the food industry, calcium oxide is utilized in clarification of cane and beet sugar juices and poultry feeding. Also can find as nutrient or dietary supplement food additive. [8]

In metallurgy, principally used as a flux in steel production but also appears in the manufacture of aluminium, magnesium and non-ferrous ores. [5]

In some states of the USA it is registered as a fungicide, insecticide ingredient. [7]

Handling considerations

Avoid breathing vapours or dusts. Avoid bodily contact with the material. If contact with the material anticipated, protective clothing and gloves, appropriate eye protection and any type of respirator prescribed. Eyewash fountains should be provided in areas where there is any possibility that workers could be exposed to the substance. Facilities for quickly drenching the body should be provided within the immediate work area where there is a possibility of exposure. [12]

The worker should wash daily at the end of each work shift, and prior to eating, drinking, smoking, etc.

Work clothing that becomes wet or significantly contaminated should be removed and replaced. [12]

Dust sources should be enclosed. Enclosures should be fitted with exhaust ventilation. Air contaminated with lime dust should be passed through cyclones or bag filters before release into general atmosphere. In case of hot lime dust, cyclones and scrubbers should be employed. Settled lime dust inside premises should be collected by industrial vacuum cleaners and manual collection should be prohibited. Ventilation in vicinity of furnaces should be designed to extract dust and gases. [12]


Molecular weight

56,077 g/mol [5]

Bulk density/Specific gravity

3,34 g/cm3 [5]


12,8 (saturated solution in water) [5]


1∙10-8S/cm on 777°C [17]

Melting point

2613°C [4]

Boiling point

2850°C [4]

Flash point

Not flammable [10]


Not flammable but may produce high heat when contact with water. [10]

Vapour density


Vapour pressure


Solubility in water

Soluble: 1,19 g/L at 20°C and 0,57 g/L at 100°C. [6]

Solubility in organic solvents

Soluble in acids, glycerol, sugar solution but insoluble in alcohol. [7]



Ionicity in water


Surface tension


Dispersion properties


Stability and reactivity

Chemical stability

Crumbles on exposure to moist air. Absorbs CO2 and H2O from air and becomes air-slaked. [5]

Reactivity hazards

Has violent reaction with water or moist air which may release toxic, corrosive or flammable gases. Reaction with water may generate high heat (as high as 800°C) which will increase the concentration of fumes in the air. [9] The solution in water is a medium strong base. [4]

Fire will produce irritating, corrosive and toxic gases. Runoff from fire control or dilution water may be corrosive, toxic and cause pollution.  [9]

Contact with metals may evolve flammable hydrogen gas. [9]

Even at low temperature calcium oxide reacts with fluorine and chlorine trifluoride, evolving high heat, flames and light. [11]

Reacts extremely violently with halogens (e.g. BF3, ClF3, HF, P2O5 and F2). [11]


corrosive [5]



Incompatibility with various substances


Special remarks on reactivity

Becomes incandescent when heated to near its melting point. [8]

The reaction of calcium oxide and boron trifluoride forms a fused mass after warming. [11]

Physical, chemical and biological coefficients






12,8 [5]


Determining a Kd-value for calcium oxide is not relevant, since this molecule reacts with water to release calcium ions and hydroxyl ions. [3]


Artificial pollution sources

Commercial production from calcination of limestone. Properly stored limestone contains 90-95% free calcium oxide and calcium carbonate, magnesium, iron, aluminium oxides as impurities. [5]

General terrestrial fate


General aquatic fate


General atmospheric fate


General persistence and degradability


Abiotic degradation and metabolites


Biodegradation and metabolites

Biotic degradation is not relevant for inorganic substances [3]


This endpoint is considered not to be relevant for calcium oxide. [3]








Soil adsorption and mobility



Measured data



General adverse effects on ecosystem

Acute toxicity (LC50, EC50)

Aquatic systems












Terrestrial systems

In aqueous suspension calcium oxide reacts basic and has toxic effect on fish. [10]

Freshwater microorganisms: 3 hours mortality, LC50= 300,4 mg CaO/L. [4]

Branchiura sowerbyi (tubificid worm): 96 hours mortality, LC50=83,0 mg CaO/L. [16]

Cyclops viridis (copepod plankton): 96 hours mortality, LC50=27,8 mg CaO/L. [16]

Oncorhynchus mykiss (freshwater fish): 96 hours mortality: LC50= 50,6 mg CaO/L. [4]

Gasterosteus aculeatus Linnaeus (marine water fish): 96 hours mortality: LC50= 457 mg CaO/L. [4]

Chronic toxicity (NOEC, LOEC)


Aquatic systems


Terrestrial systems

Freshwater algae: 72 hours mortality, NOEC= 48 mg CaO/L. [4]

Terrestrial plants: 21days, NOEC = 1 080 mg/kg soil dw (Both the read-across substance calcium dihydroxide and calcium carbonate gave similar 21-day NOEC values in OECD TG 208 studies of 1080 and 1000 mg/kg soil dw, respectively. Therefore, it may be concluded that grades of calcium oxide containing up to 35% calcium carbonate will have similar toxicity to plants. [3])

Soil macroorganisms (Eisenia fetida): Long term (14 days) mortality, NOEC = 2 000 mg/kg soil dw [3]

Soil microorganisms: dehydrogenase activity, NOEC = 4 000 mg/kg soil dw [3]


Routes of human exposures

Occupational exposure of calcium oxide may occur through inhalation of fine dust and dermal contact with the compound at workplaces where calcium oxide is produced or used. [15]

General effects

Inhalation, ingestion or contact (skin, eyes) with vapours, dusts or substance may cause severe injury, burns or death. [13]

Endocrine disruption



Calcium oxide is considered to be non-mutagenic in a Salmonella typhimurium and Escherichia coli reverse mutation assay. [4]


Neither calcium, calcium dihydroxide nor calcium carbonate are carcinogenic. Classification for carcinogenicity is not warranted. [3]


Calcium, therefore also calcium oxide, does not pose any hazard for reproduction and/or developmental toxicity. Classification for toxicity to reproduction is not warranted. [3]



Skin, eye and respiratory irritations











absorption, distribution & excretion

May produce irritation, dry skin, redness, burning sensation and contact dermatitis when contact with the moist skin is repeated or extended. [13]

Small sized particles and alkalinity of calcium oxide is highly irritating to mucous membranes, eyes and upper tract of respiratory system. There is a risk of serious damage (e.g. inflammation of respiratory passages, ulceration and perforation of nasal septum and pneumonia) as a result of local liberation of heat and dehydration of tissues. [13]

Ingestion may cause abdominal pain, abdominal cramps, vomiting and diarrhoea. [14]

Exposure limits

Immediately dangerous to life or health: 25 mg/m3. [12]

Drinking water MAC


Other information


Animal toxicity data

Acute toxicity (LD50)


Chronic toxicity (NOEL, LOEL)




Danger! According to the classification provided by companies to ECHA in REACH registrations this substance causes serious eye damage, causes skin irritation and may cause respiratory irritation.

H315: causes skin irritation. H318: causes serious eye damage. H335: may cause respiratory irritation.

Additionally, the classification provided by companies to ECHA in CLP notifications identifies that this substance causes severe skin burns and eye damage and is harmful if swallowed.

H315: causes skin irritation. H318: causes serious eye damage. H335: may cause respiratory irritation. H314: Causes severe skin burns and eye damage. H302: Harmful if swallowed. H319: Causes serious eye irritation.

EINECS regulation


OSHA regulations etc.

Permissible Exposure Limit (PEL): 8 hours-time weighted average (TWA): 5 mg/m3. [13]

Recommended Exposure Limit (REL): 10 hours-time weighted average: 2 mg/m3. [12]

Threshold Limit Values (TLV): 8 hours-time weighted average (TWA): 2 mg/m3. [13]

Excursion Limit Recommendation (ELR): excursions in worker exposure levels may exceed 3 times the TLV-TWA for no more than a total of 30 minutes during a work day, and under no circumstances should they exceed 5 times the TLV-TWA, provided that the TLV-TWA is not exceeded. [13]


Other standards, regulations and guidelines:

GHS05: corrosion. GSH07: exclamation mark.

R37: irritation to respiratory system. R38_ irritating to skin. R41: risk of serious damage to eyes.

S2: keep out of the reach of children. S25: avoid eye contact. S26: in case of contact with eyes, rinse immediately and seek medical advice. S37: wear suitable gloves. S39: wear eye/ face protection. [3]


8th of April, 2018


29th of May, 2018



[1] PubChem (Open Chemistry Database)

[2] eCHEM (The Global Portal to Information on Chemical Substances)

[3] ECHA (European Chemicals Agency)

[4] INCHEM (Chemical Safety Information from Intergovernmental Organizations)

 [5] TOXNET (Toxicology Data Network)

[6] Osol, A. (ed.). Remington's Pharmaceutical Sciences. 16th ed. Easton, Pennsylvania: Mack Publishing Co., 1980., p. 1267; through TOXNET

[7] O'Neil, M.J. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Cambridge, UK: Royal Society of Chemistry, 2013., p. 294; through TOXNET

[8] Lewis, R.J. Sr.; Hawley's Condensed Chemical Dictionary 15th Edition. John Wiley & Sons, Inc. New York, NY 2007., p. 21; through TOXNET

[9] U.S. Department of Transportation. 2012 Emergency Response Guidebook. Washington, D.C. 2012; through TOXNET

[10] European Chemicals Bureau; IUCLID Dataset, Calcium Oxide (1305-78-8). Available from, as of February 7, 2014; through TOXNET

[11] National Fire Protection Association; Fire Protection Guide to Hazardous Materials. 14TH Edition, Quincy, MA 2010, p. 491-43; through TOXNET

[12] NIOSH. NIOSH Pocket Guide to Chemical Hazards. Department of Health & Human Services, Centers for Disease Control & Prevention. National Institute for Occupational Safety & Health. DHHS (NIOSH) Publication No. 2010-168 (2010); through TOXNET

[13] American Conference of Governmental Industrial Hygienists. Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices. ACGIH, Cincinnati, OH 2014, p. 17; through TOXNET

[14] [International Program on Chemical Safety/Commission of the European Union; International Chemical Safety Card on Calcium Oxide (1305-78-8). Available from, as of 02.11.2014; through TOXNET

[15] US EPA; Inventory Update Reporting (IUR). Non-confidential 2006 IUR Records by Chemical, including Manufacturing, Processing and Use Information. Washington, DC: U.S. Environmental Protection Agency. Available from, as of Jan 13, 2014; through TOXNET

[16] Das BK, Das N; Chemosphere 61 (2): 186-91 (2005); through TOXNET

[17] IOP Science