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CHEMINFO Record Number: 10
CCOHS Chemical Name: Calcium hydroxide

Calcium dihydroxide
Calcium hydrate
Agricultural lime
Caustic lime
Hydrated lime
Lime hydrate
Lime water
Slaked lime
Hydroxyde de calcium

Chemical Name French: Hydroxyde de calcium
Chemical Name Spanish: Hidróxido de calcio
CAS Registry Number: 1305-62-0
Other CAS Registry Number(s): 1333-29-5 7719-01-9
RTECS Number(s): EW2800000
EU EINECS/ELINCS Number: 215-137-3
Chemical Family: Calcium and compounds / inorganic calcium compound / alkaline earth metal hydroxide
Molecular Formula: Ca-H2-O2
Structural Formula: Ca(OH)2


Appearance and Odour:
White crystals or soft powder or granules; impure material has gray or buff colour; odourless; readily absorbs carbon dioxide from the air to form calcium carbonate.(12,14,15)

Odour Threshold:

Warning Properties:
POOR - odourless

Commercial material has 95% purity or more. May contain magnesium hydroxide, magnesium oxide, silicon dioxide, calcium carbonate, etc. in trace amounts.

Uses and Occurrences:
Manufacture of mortar, plaster, cement and other building and paving materials; lubricants; drilling fluids; petrochemicals; fireproofing coatings; pesticides; pigments; and water-based paints; buffer and neutralizing agent; recovery of ammonia from ammonium chloride in Solvay process; caustizing soda; used in nonferrous metallurgy (used for extraction of gold and silver, recovery of nickel, tungsten, uranium, magnesia and magnesium metal; alumina production); in the iron and steel industry; water and sewage treatment; used to neutralize acid wastes; to precipitate metals from industrial effluents; flue gas desulfurization; soil conditioner; sugar refining; chemical intermediate for calcium hypochlorite, bleaching powder and calcium salts; water softening agent, food additive, component of dental cement, accelerator for low grade rubber compounds; in SBR rubber vulcanization; manufacture of paper pulp; dehairing hides.(12,13,14)


White, odourless crystals or soft powder or granules; impure material has gray or buff colour. Does not burn. Can decompose at high temperatures forming irritating calcium oxide. Very irritating to the respiratory tract. CORROSIVE. Causes severe skin and eye burns. May cause blindness and permanent scarring.


Effects of Short-Term (Acute) Exposure

Dusts or mists of concentrated solutions are likely to be very irritating to the nose, throat and upper respiratory tract, based on information for calcium oxide (calcium oxide reacts with moisture to form calcium hydroxide).

Skin Contact:
Many cases of chemical burns to the skin have been reported after exposure to wet (calcium oxide-containing) cement for as little as half an hour.(1,2,3,4,5) The calcium oxide in the cement reacts with water forming calcium hydroxide. Often, no pain is experienced immediately, so the exposure (skin contact) is allowed to continue.

Eye Contact:
Many case reports have been written about severe chemical burns of the eye cause by calcium oxide or calcium hydroxide, commonly known as "lime burns". These burns are reportedly caused most commonly by a splash of a thick, moist, pasty material (plaster, mortar or cement), less commonly by a splash of milky fluid, and rarely by a clear solution of calcium hydroxide. Solid particles react with moisture in the eye to form clumps of moist compound which are difficult to remove, resulting in a similar effect. In severe cases, the injury may be permanent and blindness may result.(6,7)

Calcium hydroxide is low in oral toxicity, based on animal information. Effects could include severe pain and burning of the mouth, throat and esophagus, stomach cramps, vomiting and diarrhea. Ingestion is not a typical route of occupational exposure.

Effects of Long-Term (Chronic) Exposure

There is no relevant animal or human information available.


There is no human or animal information available.

The International Agency for Research on Cancer (IARC) has not evaluated the carcinogenicity of this chemical.

The American Conference of Governmental Industrial Hygienists (ACGIH) has not assigned a carcinogenicity designation to this chemical.

The US National Toxicology Program (NTP) has not listed this chemical in its report on carcinogens.

Teratogenicity and Embryotoxicity:
There is no human or animal information available.

Reproductive Toxicity:
There is no human or animal information available.

There is no information available.

Toxicologically Synergistic Materials:
There is no information available.

Potential for Accumulation:
Does not accumulate in the body. Calcium ions are normally found in the body. About one third of ingested calcium ion is absorbed. Calcium ion is excreted mainly in the feces and the urine.


Remove source of contamination or have victim move to fresh air. Obtain medical advice.

Skin Contact:
Avoid direct contact. Wear chemical protective clothing, if necessary. As quickly as possible, remove contaminated clothing, shoes and leather goods (e.g. watchbands, belts). Quickly and gently blot or brush away excess chemical. Immediately flush with lukewarm, gently flowing water for at least 60 minutes. DO NOT INTERRUPT FLUSHING. If necessary, and it can be done safely, continue flushing during transport to emergency care facility. Quickly transport victim to an emergency care facility. Completely decontaminate clothing, shoes and leather goods before re-use or discard.

Eye Contact:
Avoid direct contact. Wear chemical protective gloves, if necessary. Quickly and gently blot or brush chemical off the face. Immediately flush the contaminated eye(s) with lukewarm, gently flowing water for at least 60 minutes, while holding the eyelid(s) open. If a contact lens is present, DO NOT delay irrigation or attempt to remove the lens until flushing is done. Neutral saline solution may be used as soon as it is available. DO NOT INTERRUPT FLUSHING. If necessary, continue flushing during transport to emergency care facility. Quickly transport victim to an emergency care facility.

NEVER give anything by mouth if victim is rapidly losing consciousness, is unconscious or convulsing. Have victim rinse mouth thoroughly with water. DO NOT INDUCE VOMITING. If vomiting occurs naturally, have victim rinse mouth with water again. Quickly transport victim to an emergency care facility.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest).
Consult a doctor and/or the nearest Poison Control Centre for all exposures except minor instances of inhalation.
All first aid procedures should be periodically reviewed by a doctor familiar with the material and its conditions of use in the workplace.


Flash Point:
Non-combustible (does not burn)

Lower Flammable (Explosive) Limit (LFL/LEL):
Not applicable

Upper Flammable (Explosive) Limit (UFL/UEL):
Not applicable

Autoignition (Ignition) Temperature:
Not applicable

Sensitivity to Mechanical Impact:
Probably not sensitive. Stable material.

Sensitivity to Static Charge:
Not applicable. Not combustible.

Combustion and Thermal Decomposition Products:
Calcium oxide fumes can be generated by thermal decomposition at elevated temperatures.

Fire Hazard Summary:
Calcium hydroxide will not burn or support combustion. During a fire corrosive fumes of calcium oxide may be given off. Closed containers may explode in the heat of a fire.

Extinguishing Media:
Calcium hydroxide does not burn. Use extinguishing media appropriate to the surrounding fire conditions. DO NOT use carbon dioxide as an extinguishing agent.

Fire Fighting Instructions:
Evacuate area and fight fire from a safe distance or a protected location. Approach fire from upwind. If possible, isolate materials not involved in the fire and protect personnel.
Move containers from fire area if it can be done without risk. Otherwise, use water in flooding quantities as a spray or fog to keep fire-exposed containers cool and absorb heat to help prevent rupture. Water spray may also be used to knock down irritating/toxic combustion products which may be produced in a fire. Apply water from as far a distance as possible.
At high temperatures, decomposition occurs giving off strong, corrosive fumes of calcium oxide. Do not enter without wearing specialized protective equipment suitable for the situation. Firefighter's normal protective clothing (Bunker Gear) will not provide adequate protection. Chemical resistant clothing (e.g. chemical splash suit) and positive pressure self-contained breathing apparatus (MSHA/NIOSH approved or equivalent) may be necessary.


NFPA - Comments:
NFPA has no listing for this chemical in Codes 49 or 325.


Molecular Weight: 74.10

Conversion Factor:
Not applicable

Physical State: Solid
Melting Point: Not applicable (decomposes).
Boiling Point: Not applicable (decomposes).
Decomposition Temperature: 580 deg C (1076 deg F) (15)
Relative Density (Specific Gravity): 2.24 at 20 deg C (water = 1) (15)
Solubility in Water: 0.185 g/100 mL at 0 deg C; 0.071 g/100 mL at 100 deg C (14)
Solubility in Other Liquids: Soluble in acids, glycerol and ammonia salt solutions; insoluble in ethanol.(12,15)
Coefficient of Oil/Water Distribution (Partition Coefficient): Not available
pH Value: 11.3 (0.01% at 25 deg C); 12.5 to 12.7 (saturated solution (0.18 g/100 mL) at 25 deg C) (14,15)
Vapour Density: Not applicable
Vapour Pressure: Zero (does not form vapour)
Saturation Vapour Concentration: Not applicable
Evaporation Rate: Not applicable


Normally stable. Absorbs carbon dioxide from the air to form calcium carbonate.(14,15)

Hazardous Polymerization:
Does not occur.

Incompatibility - Materials to Avoid:

NOTE: Chemical reactions that could result in a hazardous situation (e.g. generation of flammable or toxic chemicals, fire or detonation) are listed here. Many of these reactions can be done safely if specific control measures (e.g. cooling of the reaction) are in place. Although not intended to be complete, an overview of important reactions involving common chemicals is provided to assist in the development of safe work practices.

STRONG ACIDS (e.g. sulfuric acid) - may react violently.(16)
MALEIC ANHYDRIDE - may react explosively with decomposition.(17)
NITROALKANES (e.g. nitromethane, nitroethane, nitropropane) - react to form explosive salts.(17)
PHOSPHORUS - yields phosphines which may ignite spontaneously in air.(17)

Hazardous Decomposition Products:
Calcium carbonate.

Conditions to Avoid:
High temperatures, generation of dust .

Corrosivity to Metals:
Corrosive to aluminum.(18) Not corrosive to certain grades of stainless steel (302, 304, 316, 410, 430) at room temperature and to nickel-chromium-molybdenum alloy.(15,18)

Stability and Reactivity Comments:
Calcium hydroxide reacts readily with carbon dioxide in air to form calcium carbonate.(14,15) Attacks some metals.(19)


LD50 (oral, rat): 7340 mg/kg (8)
LD50 (oral, mouse): 7300 mg/kg (9, unconfirmed)

Eye Irritation:

Application of 10 mg (0.01 g) of solid calcium hydroxide caused severe irritation or corrosion in rabbits in a modified Draize test. Healing did not occur within 21 days.(10) Injury to the corneas of rabbits resulted from exposure to a paste of calcium hydroxide for 1 minute, followed by cleaning and rinsing with a physiological salt solution. This injury reached a maximum at 24 hours after exposure and the eye had not returned to normal after 3 months.(11) Further details on this study are not available.

Effects of Long-Term (Chronic) Exposure:

Male rats were given tap water containing 50 or 350 mg/L. At 2 months, the rats were restless, aggressive and had reduced food intake. At 3 months, there was a decrease in body weight and a decrease in certain blood components (for example, red blood cells, hemoglobin).(11) Further details on this study were not available. Its relevance to occupational exposures is questionable.


Selected Bibliography:
(1) Vickers, H.R., et al. Cement burns. Contact Dermatitis. Vol. 2 (1976). p. 73-78
(2) Buckley, D.B. Skin burns due to wet cement. Contact Dermatitis. Vol. 8, no. 6 (1982). p. 407-409.
(3) Tosti, A., et al. Skin burns due to transit-mixed Portland cement. Contact Dermatitis. Vol. 21, no. 1 (1989). p. 58
(4) Hannuksela, M., et al. Caustic ulcers caused by cement. British Journal of Dermatology. Vol. 95 (1976). p. 547-549.
(5) Flowers, M.W. Burn hazard with cement. British Medical Journal. Vol. 1, no. 6122. (May, 1978). p. 1250.
(6) Grant, W.M., et al. Toxicology of the eye. 4th edition. Charles C. Thomas, 1993. p. 298-302
(7) McLaughlin, R.S. Chemical burns of the human cornea. American Journal of Ophthalmology. Vol. 20, no. 11 (November, 1946). p. 1355- 1362.
(8) Smyth Jr., H.F., et al. Range-finding toxicity data: list VII. American Industrial Hygiene Association Journal. Vol. 30, no. 5 (September-October, 1969). p. 470-476
(9) RTECS record for calcium hydroxide. Date of last update: 9504.
(10) Griffith, J.F., et al. Dose-response studies with chemical irritants in the Albino rabbit eye as a basis for selecting optimum testing conditions for predicting hazard to the human eye. Toxicology and Applied Pharmacology. Vol. 55 (1980). p. 501-513
(11) Pierce, J. O. Alkaline materials. In: Patty's industrial hygiene and toxicology. 4th edition. Edited by G.D. Clayton, et al. Volume II, Part A. John Wiley and Sons, 1993. p. 762-764
(12) HSDB record for calcium hydroxide. Date of last revision: 96/03/21
(13) Petersen, R.L., et al. Calcium compounds: survey. In: Kirk-Othmer encyclopedia of chemical technology. 4th edition. Volume 4. John Wiley and Sons, 1992. p. 788-796
(14) Oates, T. Lime and limestone In: Ullmann's encyclopedia of industrial chemistry. 5th completely revised edition. Volume A 15. VCH Verlagsgesellschaft, 1990. p. 334-345
(15) Environmental and technical information for problem spills: calcium oxide and hydroxide. Environmental Protection Service, Environment Canada, March, 1984
(16) The Sigma-Aldrich library of chemical safety data. Edition II. Volume 1. Sigma-Aldrich Corporation, 1988. p. 667B
(17) Fire protection guide to hazardous materials. 11th edition. National Fire Protection Association, 1994. NFPA 491
(18) Corrosion data survey: metals section. 6th edition. National Association of Corrosion Engineers, 1985. p. 30-1 to 31-1
(19) NIOSH pocket guide to chemical hazards. National Institute for Occupational Safety and Health, June 1994. p. 46-47
(20) Forsberg, K., et al. Quick selection guide to chemical protective clothing. 4th ed. Van Nostrand Reinhold, 2002
(21) Occupational Safety and Health Administration (OSHA). Metal and Metalloid Particulates in Workplace Atmospheres. In: OSHA Analytical Methods Manual. Revision Date: Oct. 31, 2001. Available at: <>
(22) National Institute for Occupational Safety and Health (NIOSH). Calcium and compounds as Ca. In: NIOSH Manual of Analytical Methods (NMAM(R)). 4th ed. Edited by M.E. Cassinelli, et al. DHHS (NIOSH) Publication 94-113. Aug. 1994. Available at: <>

Information on chemicals reviewed in the CHEMINFO database is drawn from a number of publicly available sources. A list of general references used to compile CHEMINFO records is available in the database Help.

Review/Preparation Date: 1996-11-08

Revision Indicators:
Resistance of material 1998-05-01
Bibliography 1998-05-01
PEL-TWA final 2003-12-04
PEL final comments 2003-12-04
PEL-TWA transitional 2003-12-04
PEL transitional comments 2003-12-04
Resistance of materials for PPE 2004-04-05
Bibliography 2004-04-05
Bibliography 2005-03-09
Sampling/analysis 2005-03-09
Sampling/analysis 2005-03-28

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