Calcium Hydroxide

1Identification

Name

Calcium Hydroxide

IUPAC name

calcium dihydroxide

CAS number

1305-62-0

Molecular formula

CaH2O2

Molecular weight

74.09 g/mol

InChIKey

AXCZMVOFGPJBDE-UHFFFAOYSA-L

SMILES

[OH-].[OH-].[Ca+2]

PubChem CID

6093208

Synonyms

CALCIUM HYDROXIDE, Slaked lime, Hydrated lime, Lime hydrate, Calcium hydrate, Lime water, Calcium hydroxide (Ca(OH)2), Hydralime, Slaked-lime, Lime milk, Calcarea caustica, INS NO.526, E-526, Hydroxide, Calcium

Recommended uses

• CIR ingredient: Calcium Hydroxide
  Cosmetic Ingredient Review (CIR)
• Used in mortar, plaster, cement, lubricants, drilling fluids, paper pulp, and water treatment; also used to dehair hides; [ACGIH] Used in pesticides, fireproofing coatings, water-based paints, SBR rubber vulcanization, binding and paving materials, soil treatments, brewing manufacture, dental cements, petrochemicals, as chemical intermediate, buffering agent for metals, pearls, and celluloid, disinfectant, food additive, for ammonia recovery in gas manufacture, purification of sugar juices, to preserve eggs and apples during storage, in cattle feeds, and veterinary medicine; [HSDB] Used as both an inert and active ingredient (microbiocide/microbiostat) in pesticide products;
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• Petroleum Production and Refining [Category: Industry] Pulp and Paper Processing [Category: Industry] Painting (Pigments, Binders, and Biocides) [Category: Paint] Using Disinfectants or Biocides [Category: Clean] Farming (Pesticides) [Category: Industry] Sewer and Wastewater Treatment [Category: Industry] Leather Tanning and Processing [Category: Industry] Cement Producing [Category: Industry] Farming (Feed Additives) [Category: Industry]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• Other Binder Lubricating agent Processing aids not otherwise specified Chemical reaction regulator Fuel agents pH regulating agent Fuel Antioxidant Flux agent Absorbent Dehydrating agent (desiccant) Sealant (barrier) Reducing agent Stabilizing agent Flow promoter Catalyst Filler Diluent Not Known or Reasonably Ascertainable Corrosion inhibitor Soil amendments (fertilizers) Solids separation (precipitating) agent, not otherwise specified Hardener Flocculating agent Adhesion/cohesion promoter Processing aids, specific to petroleum production Intermediate Softener and conditioner Oxidizing agent Adsorbent
  EPA Chemical Data Reporting (CDR)
• Chemical reaction regulator pH regulating agent Other Lubricating agent Adhesion/cohesion promoter Flocculating agent Heat stabilizer Intermediate Reducing agent Soil amendments (fertilizers) Filler Not Known or Reasonably Ascertainable Absorbent
  EPA Chemical Data Reporting (CDR)

Use categories: EPA Safer Chemical Functional Use Classes -> Processing Aids and Additives · Safer Chemical Classes -> Green circle - The chemical has been verified to be of low concern · Food additives · Food Additives -> ACIDITY_REGULATOR; FIRMING_AGENT -> JECFA Functional Classes

Description

• Calcium hydroxide is an odorless white granules. Sinks in water. (USCG, 1999)
  CAMEO Chemicals
• Calcium dihydroxide is a calcium hydroxide. It has a role as an astringent.
  ChEBI
• The CIR Expert Panel concluded that ... Calcium Hydroxide is safe in hair straighteners and depilatories under conditions of recommended use; users should minimize skin contact. These ingredients are safe for all other present practices of use and concentration described in this safety assessment when formulated to be nonirritating.
  Cosmetic Ingredient Review (CIR)

2Hazard identification

Signal word

Danger

Pictograms

GHS05, GHS07

Classification source

European Chemicals Agency (ECHA)

Precautionary statements

Other reported classifications

5 classification records exist across sources. Differences usually reflect purity, physical form or impurities.

Health hazards

• Dust irritates eyes, nose and throat. (USCG, 1999)
  CAMEO Chemicals

Fire hazards

• Not combustible.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Hazards summary

• A moderately caustic irritant; [ACGIH] Can cause skin burns and blisters; [ICSC] Corrosive to skin; [Quick CPC] Causes burns; [Alfa Aesar MSDS]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases

3Composition / information on ingredients

This page describes the pure substance. Commercial products may be solutions or mixtures. Check Section 3 of your supplier's SDS for concentrations and other ingredients.

4First-aid measures

• Excerpt from NIOSH Pocket Guide for Calcium hydroxide: Eye: IRRIGATE IMMEDIATELY - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately. Skin: SOAP FLUSH IMMEDIATELY - If this chemical contacts the skin, immediately flush the contaminated skin with soap and water. If this chemical penetrates the clothing, immediately remove the clothing and flush the skin with water. If irritation persists after washing, get medical attention. Breathing: RESPIRATORY SUPPORT - If a person breathes large amounts of this chemical, move the exposed person to fresh air at once.
  CAMEO Chemicals
• (General first aid procedures) Eye: Irrigate immediately - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately. Skin: Soap flush immediately - If this chemical contacts the skin, immediately flush the contaminated skin with soap and water. If this chemical penetrates the clothing, immediately remove the clothing and flush the skin with water. If irritation persists after washing, get medical attention. Breathing: Respiratory support Swallow: Medical attention immediately - If this chemical has been swallowed, get medical attention immediately.
  The National Institute for Occupational Safety and Health (NIOSH)

Symptoms of exposure

• Sore throat. Cough. Burning sensation.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Redness. Roughness. Pain. Dry skin. Skin burns. Blisters.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Redness. Pain. Severe deep burns.
  ILO-WHO International Chemical Safety Cards (ICSCs)

5Fire-fighting measures

• Skin: Remove contaminated clothes. Rinse skin with plenty of water or shower. Refer for medical attention .
  Hazardous Substances Data Bank (HSDB)
• Inhalation: Fresh air, rest. Refer for medical attention.
  Hazardous Substances Data Bank (HSDB)
• In case of fire in the surroundings, use appropriate extinguishing media.
  Hazardous Substances Data Bank (HSDB)

6Accidental release measures

Spill cleanup

• Personal protection: particulate filter respirator adapted to the airborne concentration of the substance. Sweep spilled substance into covered containers. Then store and dispose of according to local regulations.
  ILO-WHO International Chemical Safety Cards (ICSCs)

7Handling and storage

• Separated from strong acids.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Keep well closed.
  Hazardous Substances Data Bank (HSDB)
• ... Preserved in well-filled, tight containers, at a temp not exceeding 25 °C. /Calcium hydroxide topical soln/
  Hazardous Substances Data Bank (HSDB)
• Store under tightly capped conditions.
  Hazardous Substances Data Bank (HSDB)

8Exposure controls / personal protection

Personal protective equipment

• Excerpt from NIOSH Pocket Guide for Calcium hydroxide: Skin: PREVENT SKIN CONTACT - Wear appropriate personal protective clothing to prevent skin contact. Eyes: PREVENT EYE CONTACT - Wear appropriate eye protection to prevent eye contact. Wash skin: • WHEN CONTAMINATED - The worker should immediately wash the skin when it becomes contaminated. • DAILY - The worker should wash daily at the end of each work shift, and prior to eating, drinking, smoking, etc. Remove: WHEN WET OR CONTAMINATED - Work clothing that becomes wet or significantly contaminated should be removed and replaced.
  CAMEO Chemicals
• ... Protective equipment incl workclothes of resistant material, canvas hand protection, eye & face protection & resp protective equipment should be worn & exposed skin ... coated with vaseline or oil.
  Hazardous Substances Data Bank (HSDB)
• Dust-proof goggles and mask.
  Hazardous Substances Data Bank (HSDB)
• Wear appropriate personal protective clothing to prevent skin contact.
  Hazardous Substances Data Bank (HSDB)

Respirator recommendations

• Important additional information about respirator selection
  The National Institute for Occupational Safety and Health (NIOSH)

9Physical and chemical properties

10Stability and reactivity

Reactivity

• The nitroparaffins, nitromethane, nitropropane, etc. form salts with inorganic bases such as CALCIUM HYDROXIDE. The dry salts are explosive [Chem. Eng. news 30:2344 1952]. Bases are chemically similar to sodium hydroxide (NaOH) or sodium oxide (Na2O). They neutralize acids exothermically to form salts plus water. When soluble in water they give solutions having a pH greater than 7.0. Mixing these materials with water can generate troublesome amounts of heat as the base is dissolved or diluted. Bases react with certain metals (such as aluminum and zinc) to form oxides or hydroxides of the metal and generate gaseous hydrogen.
  CAMEO Chemicals
• Water soluble. The amount of heat generated by hydrolysis may be large.
  CAMEO Chemicals

Incompatible materials and hazardous reactions

• Phosphorus boiled with alkaline hydroxides yields mixed phosphines which may ignite spontaneously in air.
  Hazardous Substances Data Bank (HSDB)
• When chlorinated phenols are heated for analytical purposes with calcium hydroxide-potassium nitrate mixtures, chlorinated benzodioxins analogous to the extremely toxic tetrachlorodibenzodioxin may be formed.
  Hazardous Substances Data Bank (HSDB)
• The self-heating and decomposition of /1,3,5-trinitrohexahydro-1,3,5-triazine, calcium hydroxide and water/ was studied ... in a sealed capsule and in a larger scale furnace test. A rapid exothermic decomposition reaction can be initiated at 100 °C or below, and may lead to spontaneous ignition and then deflagration or detonation.
  Hazardous Substances Data Bank (HSDB)

Chemical stability

• Readily absorbs carbon dioxide from air forming calcium carbonate.
  Hazardous Substances Data Bank (HSDB)

11Toxicological information

Target organs

• Eyes, skin, respiratory system
  The National Institute for Occupational Safety and Health (NIOSH)

Short-term exposure effects

• The substance is corrosive to the eyes and skin. The substance is irritating to the respiratory tract. Medical observation is indicated.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Long-term exposure effects

• Repeated or prolonged contact with skin may cause dermatitis. Repeated or prolonged inhalation of dust particles may cause effects on the lungs.
  ILO-WHO International Chemical Safety Cards (ICSCs)

12Ecological information

Not available in the public sources we compile. Check Section 12 of the supplier's SDS.

13Disposal considerations

• SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational harm/injury/toxicity or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal and plant life; and conformance with environmental and public health regulations.
  Hazardous Substances Data Bank (HSDB)
• SRP: Wastewater from contaminant suppression, cleaning of protective clothing/equipment, or contaminated sites should be contained and evaluated for subject chemical or decomposition product concentrations. Concentrations shall be lower than applicable environmental discharge or disposal criteria. Alternatively, pretreatment and/or discharge to a permitted wastewater treatment facility is acceptable only after review by the governing authority and assurance that "pass through" violations will not occur. Due consideration shall be given to remediation worker exposure (inhalation, dermal and ingestion) as well as fate during treatment, transfer and disposal.
  Hazardous Substances Data Bank (HSDB)

14Transport information

Not available in the public sources we compile. Check Section 14 of the supplier's SDS.

How DOT hazard classes work →

15Regulatory information

• Residues of calcium hydroxide are exempted from the requirement of a tolerance when used in accordance with good agricultural practice as inert (or occasionally active) ingredients in pesticide formulations applied to growing crops or to raw agricultural commodities after harvest. Use: solid diluent, carrier.
  Hazardous Substances Data Bank (HSDB)
• As the federal pesticide law FIFRA directs, EPA is conducting a comprehensive review of older pesticides to consider their health and environmental effects and make decisions about their continued use. Under this pesticide reregistration program, EPA examines newer health and safety data for pesticide active ingredients initially registered before November 1, 1984, and determines whether the use of the pesticide does not pose unreasonable risk in accordance to newer saftey standards, such as those described in the Food Quality Protection Act of 1996.
  Hazardous Substances Data Bank (HSDB)
• Substance added directly to human food affirmed as generally recognized as safe (GRAS).
  Hazardous Substances Data Bank (HSDB)

Overview of SDS regulations (OSHA HazCom, WHMIS, REACH/CLP) →

16Other information

Compiled from PubChem CID 6093208 and the sources it aggregates (attributed inline). Data retrieved 2026-10-12. This summary describes the pure substance and is not a supplier SDS.