Aluminum hydroxide

Aluminium hydroxide

Names
Preferred IUPAC name Aluminium hydroxide
Systematic IUPAC name Aluminium(3+) trioxidanide
Other names Aluminic acid Aluminic hydroxide Aluminium(III) hydroxide Aluminium hydroxide Hydrated alumina Orthoaluminic acid
Identifiers
CAS Number	21645-51-2 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:33130 Y
ChEMBL	ChEMBL1200706 N
ChemSpider	8351587 Y
ECHA InfoCard	100.040.433
PubChem	10176082
RTECS number	BD0940000
UNII	5QB0T2IUN0 Y
InChI InChI=1S/Al.3H2O/h;3*1H2/q+3;;;/p-3 Y Key: WNROFYMDJYEPJX-UHFFFAOYSA-K A02AB02 (WHO) (algeldrate) N InChI=1/Al.3H2O/h;3*1H2/q+3;;;/p-3 Key: WNROFYMDJYEPJX-DFZHHIFOAJ
SMILES [OH-].[OH-].[OH-].[Al+3]
Properties
Chemical formula	Al(OH)3
Molar mass	78.00 g/mol
Appearance	White amorphous powder
Density	2.42 g/cm3, solid
Melting point	300 °C (572 °F; 573 K)
Solubility in water	0.0001 g/100 mL (20 °C)
Solubility product (Ksp)	3×10−34
Solubility	soluble in acids, alkalis, HCl, H2SO4
Acidity (pKa)	>7
Thermochemistry
Std enthalpy of formation (ΔfHo298)	−1277 kJ·mol−1
Pharmacology
ATC code	A02AB01 (WHO)
Hazards
Safety data sheet	External MSDS
EU classification (DSD)	Irritant (I) Xi
R-phrases	R36 R37 R38
S-phrases	S26 S36
NFPA 704	0 1 0
Flash point	Non-flammable
Related compounds
Other anions	None
Related compounds	Sodium oxide, aluminium oxide hydroxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Aluminic hydroxide
Aluminium(III) hydroxide
Aluminium hydroxide
Hydrated alumina

Aluminium hydroxide, Al(OH)₃, is found in nature as the mineral gibbsite (also known as hydrargillite) and its three much rarer polymorphs: bayerite, doyleite and nordstrandite. Aluminium hydroxide is amphoteric in nature, i.e, it has both basic and acidic nature. Closely related are aluminium oxide hydroxide, AlO(OH), and aluminium oxide (or alumina), Al₂O₃. Aluminium oxide is also amphoteric in nature. These compounds together are the major components of the aluminium ore bauxite.

The naming for the different forms of aluminium hydroxide is ambiguous and there is no universal standard. All four polymorphs have a chemical composition of aluminium trihydroxide (an aluminium atom attached to three hydroxide groups).

Gibbsite is also known as hydrargillite, named after the Greek words for water (hydra) and clay (argylles). The first compound named hydrargillite was thought to be aluminium hydroxide, but was later found to be aluminium phosphate; despite this, both gibbsite and hydrargillite are used to refer to the same polymorphism of aluminium hydroxide, with gibbsite used most commonly in the United States and hydrargillite used more often in Europe. In 1930 it was referred to as α-alumina trihydrate to contrast it with bayerite which was called β-alumina trihydrate (the alpha and beta designations were used to differentiate the more- and less-common forms respectively). In 1957 a symposium on alumina nomenclature attempted to develop a universal standard, resulting in gibbsite being designated γ-Al(OH)₃ and bayerite becoming α-Al(OH)₃ and nordstrandite being designated Al(OH)₃. Based on their crystallographic properties, a suggested nomenclature and designation is for gibbsite to be α-Al(OH)₃, bayerite to be designated β-Al(OH)₃ and both nordstrandite and doyleite are designated Al(OH)₃. Under this designation, the α and β prefixes refer to hexagonal, close-packed structures and altered or dehydrated polymorphisms respectively, with no differentiation between nordstrandite and doyleite.