Calcium hydroxide

Calcium hydroxide
Names
	IUPAC name Calcium hydroxide
	Other names Slaked lime; Milk of lime; Calcium(II) hydroxide; Pickling lime; Hydrated lime; Portlandite; Calcium hydrate; Calcium dihydroxide;
Identifiers
CAS Number	1305-62-0 ;
3D model (JSmol)	Interactive image; Interactive image;
ChEBI	CHEBI:31341 ;
ChemSpider	14094 ;
ECHA InfoCard	100.013.762
EC Number	215-13;
E number	E526 (acidity regulators, ...)
Gmelin Reference	846915
KEGG	D01083 ;
PubChem CID	14777;
RTECS number	EW2800000;
UNII	PF5DZW74VN ;
CompTox Dashboard (EPA)	DTXSID7034410 ;
	InChI InChI=1S/Ca.2H2O/h;21H2/q+2;;/p-2 Key: AXCZMVOFGPJBDE-UHFFFAOYSA-L ; InChI=1/Ca.2H2O/h;21H2/q+2;;/p-2 Key: AXCZMVOFGPJBDE-NUQVWONBAD;
	SMILES [Ca+2].[OH-].[OH-]; [OH-].[OH-].[Ca+2];
Properties
Chemical formula	Ca(OH)2
Molar mass	74.093 g/mol
Appearance	White powder
Odor	Odorless
Density	2.211 g/cm3, solid
Melting point	580 °C (1,076 °F; 853 K) (loses water, decomposes)
Solubility in water	1.89 g/L (0 °C); 1.73 g/L (20 °C); 0.66 g/L (100 °C); (retrograde solubility, i.e., unusually decreasing with T);
Solubility product (Ksp)	5.02×10−6
Solubility	Soluble in glycerol and acids.; Insoluble in ethanol.;
Acidity (pKa)	pKa1 = 12.63; pKa2 = 11.57
Magnetic susceptibility (χ)	−22.0·10−6 cm3/mol
Refractive index (nD)	1.574
Structure
Crystal structure	Hexagonal, hP3
Space group	P3m1 No. 164
Lattice constant	a = 0.35853 nm, c = 0.4895 nm
Thermochemistry
Std molar; entropy (S⦵298)	83 J·mol−1·K−1
Std enthalpy of; formation (ΔfH⦵298)	−987 kJ·mol−1
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314, H335, H402
Precautionary statements	P261, P280, P305+P351+P338
NFPA 704 (fire diamond)	3 0 0
Flash point	Non-flammable
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	7340 mg/kg (oral, rat) ; 7300 mg/kg (mouse)
	NIOSH (US health exposure limits):
PEL (Permissible)	TWA 15 mg/m3 (total) 5 mg/m3 (resp.)
REL (Recommended)	TWA 5 mg/m3
IDLH (Immediate danger)	N.D.
Safety data sheet (SDS)
Related compounds
Other cations	Magnesium hydroxide; Strontium hydroxide; Barium hydroxide
Related bases	Calcium oxide
Supplementary data page
	Calcium hydroxide (data page)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca(OH)₂. It is a colorless crystal or white powder and is produced when quicklime (calcium oxide) is mixed with water. Annually, approximately 125 million tons of calcium hydroxide are produced worldwide.^[8]

Calcium hydroxide has many names including hydrated lime, caustic lime, builders' lime, slaked lime, cal, and pickling lime. Calcium hydroxide is used in many applications, including food preparation, where it has been identified as E number E526. Limewater, also called milk of lime, is the common name for a saturated solution of calcium hydroxide.

^ John Rumble (18 June 2018). CRC Handbook of Chemistry and Physics (99 ed.). CRC Press. pp. 5–188. ISBN 978-1138561632.
^ "Sortierte Liste: pKb-Werte, nach Ordnungszahl sortiert. – Das Periodensystem online".
^ ChemBuddy dissociation constants pK_a and pK_b
^ Petch, H. E. (1961). "The hydrogen positions in portlandite, Ca(OH)₂, as indicated by the electron distribution". Acta Crystallographica. 14 (9): 950–957. Bibcode:1961AcCry..14..950P. doi:10.1107/S0365110X61002771.
^ ^a ^b Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A21. ISBN 978-0-618-94690-7.
^ "MSDS Calcium hydroxide" (PDF). Archived from the original (PDF) on 25 March 2012. Retrieved 21 June 2011.
^ ^a ^b ^c NIOSH Pocket Guide to Chemical Hazards. "#0092". National Institute for Occupational Safety and Health (NIOSH).
^ Cite error: The named reference Ullmann was invoked but never defined (see the help page).

[crc-1] John Rumble (18 June 2018). CRC Handbook of Chemistry and Physics (99 ed.). CRC Press. pp. 5–188. ISBN 978-1138561632.

[2] "Sortierte Liste: pKb-Werte, nach Ordnungszahl sortiert. – Das Periodensystem online".

[3] ChemBuddy dissociation constants pK_a and pK_b

[4] Petch, H. E. (1961). "The hydrogen positions in portlandite, Ca(OH)₂, as indicated by the electron distribution". Acta Crystallographica. 14 (9): 950–957. Bibcode:1961AcCry..14..950P. doi:10.1107/S0365110X61002771.

[b1-5] Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A21. ISBN 978-0-618-94690-7.

[avantormaterials-6] "MSDS Calcium hydroxide" (PDF). Archived from the original (PDF) on 25 March 2012. Retrieved 21 June 2011.

[PGCH-7] NIOSH Pocket Guide to Chemical Hazards. "#0092". National Institute for Occupational Safety and Health (NIOSH).

[Ullmann-8] Cite error: The named reference Ullmann was invoked but never defined (see the help page).

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