Calcium hydroxide

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
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.013.762 Edit this at Wikidata
EC Number
  • 215-13
E number E526 (acidity regulators, ...)
846915
KEGG
RTECS number
  • EW2800000
UNII
  • InChI=1S/Ca.2H2O/h;2*1H2/q+2;;/p-2 checkY
    Key: AXCZMVOFGPJBDE-UHFFFAOYSA-L checkY
  • InChI=1/Ca.2H2O/h;2*1H2/q+2;;/p-2
    Key: AXCZMVOFGPJBDE-NUQVWONBAD
  • [Ca+2].[OH-].[OH-]
  • [OH-].[OH-].[Ca+2]
Properties
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)
  • 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)
5.02×10−6 [1]
Solubility
Acidity (pKa) pKa1 = 12.63
pKa2 = 11.57[2][3]
−22.0·10−6 cm3/mol
1.574
Structure
Hexagonal, hP3[4]
P3m1 No. 164
a = 0.35853 nm, c = 0.4895 nm
Thermochemistry
83 J·mol−1·K−1[5]
−987 kJ·mol−1[5]
Hazards
GHS labelling:
GHS05: Corrosive GHS07: Exclamation mark
Danger
H314, H335, H402
P261, P280, P305+P351+P338
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
0
0
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
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.)[7]
REL (Recommended)
 TWA 5 mg/m3[7]
IDLH (Immediate danger)
 N.D.[7]
Safety data sheet (SDS) [6]
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).
checkY verify (what is checkY☒N ?)

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.

  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 pKa and pKb
  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.
  5. ^ a b Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A21. ISBN 978-0-618-94690-7.
  6. ^ "MSDS Calcium hydroxide" (PDF). Archived from the original (PDF) on 25 March 2012. Retrieved 21 June 2011.
  7. ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0092". National Institute for Occupational Safety and Health (NIOSH).
  8. ^ Cite error: The named reference Ullmann was invoked but never defined (see the help page).