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 properties. Closely related are aluminium oxide hydroxide, AlO(OH), and aluminium oxide or alumina (Al2O3), the latter of which is also amphoteric. These compounds together are the major components of the aluminium ore bauxite.
|Preferred IUPAC name
|Systematic IUPAC name
3D model (JSmol)
|Molar mass||78.00 g/mol|
|Appearance||White amorphous powder|
|Density||2.42 g/cm3, solid|
|Melting point||300 °C (572 °F; 573 K)|
|0.0001 g/100 mL|
Solubility product (Ksp)
|Solubility||soluble in acids and alkalis|
Std enthalpy of
|Safety data sheet||External MSDS|
|P264, P261, P280, P271, P312, P304+340, P305+351+338, P337+313|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|>5000 mg/kg (rat, oral)|
aluminium oxide hydroxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (one 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, 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.
Gibbsite has a typical metal hydroxide structure with hydrogen bonds. It is built up of double layers of hydroxyl groups with aluminium ions occupying two-thirds of the octahedral holes between the two layers.
Four polymorphs of aluminium hydroxide exist, all based on the common combination of one aluminium atom and three hydroxide molecules into different crystalline arrangements that determine the appearance and properties of the compound. The four combinations are:
All polymorphs are composed of layers of octahedral aluminium hydroxide units with the aluminium atom in the centre and the hydroxyl groups on the sides, with hydrogen bonds holding the layers together. The polymorphisms vary in how the layers stack together, with the arrangements of the molecules and layers determined by the acidity, presence of ions (including salt) and the surface of the minerals the substance forms on. Under most conditions, gibbsite is the most chemically stable form of aluminium hydroxide. All forms of Al(OH)3 crystals are hexagonal.
Virtually all the aluminium hydroxide used commercially is manufactured by the Bayer process which involves dissolving bauxite in sodium hydroxide at temperatures up to 270 °C (518 °F). The waste solid, bauxite tailings, is removed and aluminium hydroxide is precipitated from the remaining solution of sodium aluminate. This aluminium hydroxide can be converted to aluminium oxide or alumina by calcination.
The residue or bauxite tailings, which is mostly iron oxide, is highly caustic due to residual sodium hydroxide. It was historically stored in lagoons; this led to the Ajka alumina plant accident in 2010 in Hungary, where a dam bursting led to the drowning of nine people. An additional 122 sought treatment for chemical burns. The mud contaminated 40 square kilometres (15 sq mi) of land and reached the Danube. While the mud was considered non-toxic due to low levels of heavy metals, the associated slurry had pH of 13.
One of the major uses of aluminium hydroxide is as a feedstock for the manufacture of other aluminium compounds: speciality calcined aluminas, aluminium sulfate, polyaluminium chloride, aluminium chloride, zeolites, sodium aluminate, activated alumina, and aluminium nitrate.
Freshly precipitated aluminium hydroxide forms gels, which are the basis for the application of aluminium salts as flocculants in water purification. This gel crystallizes with time. Aluminium hydroxide gels can be dehydrated (e.g. using water-miscible non-aqueous solvents like ethanol) to form an amorphous aluminium hydroxide powder, which is readily soluble in acids. Aluminium hydroxide powder which has been heated to an elevated temperature under carefully controlled conditions is known as activated alumina and is used as a desiccant, as an adsorbent in gas purification, as a Claus catalyst support for water purification, and as an adsorbent for the catalyst during the manufacture of polyethylene by the Sclairtech process.
Aluminium hydroxide also finds use as a fire retardant filler for polymer applications in a similar way to magnesium hydroxide and mixtures of huntite and hydromagnesite. It decomposes at about 180 °C (356 °F), absorbing a considerable amount of heat in the process and giving off water vapour. In addition to behaving as a fire retardant, it is very effective as a smoke suppressant in a wide range of polymers, most especially in polyesters, acrylics, ethylene vinyl acetate, epoxies, PVC and rubber.
Under the generic name "algeldrate", aluminium hydroxide is used as an antacid in humans and animals (mainly cats and dogs). It is preferred over other alternatives such as sodium bicarbonate because Al(OH)3, being insoluble, does not increase the pH of stomach above 7 and hence, does not trigger secretion of excess acid by the stomach. Brand names include Alu-Cap, Aludrox, Gaviscon or Pepsamar. It reacts with excess acid in the stomach, reducing the acidity of the stomach content, which may relieve the symptoms of ulcers, heartburn or dyspepsia. Such products can cause constipation, because the aluminium ions inhibit the contractions of smooth muscle cells in the gastrointestinal tract, slowing peristalsis and lengthening the time needed for stool to pass through the colon. Some such products (such as Maalox) are formulated to minimize such effects through the inclusion of equal concentrations of magnesium hydroxide or magnesium carbonate, which have counterbalancing laxative effects.
This compound is also used to control hyperphosphatemia (elevated phosphate, or phosphorus, levels in the blood) in people and animals suffering from kidney failure. Normally, the kidneys filter excess phosphate out from the blood, but kidney failure can cause phosphate to accumulate. The aluminium salt, when ingested, binds to phosphate in the intestines and reduce the amount of phosphorus that can be absorbed.
Precipitated aluminium hydroxide is included as an adjuvant in some vaccines (e.g. anthrax vaccine). One of the well-known brands of aluminium hydroxide adjuvant is Alhydrogel, made by Brenntag Biosector. Since it absorbs protein well, it also functions to stabilize vaccines by preventing the proteins in the vaccine from precipitating or sticking to the walls of the container during storage. Aluminium hydroxide is sometimes called "alum", a term generally reserved for one of several sulfates.
Vaccine formulations containing aluminium hydroxide stimulate the immune system by inducing the release of uric acid, an immunological danger signal. This strongly attracts certain types of monocytes which differentiate into dendritic cells. The dendritic cells pick up the antigen, carry it to lymph nodes, and stimulate T cells and B cells. It appears to contribute to induction of a good Th2 response, so is useful for immunizing against pathogens that are blocked by antibodies. However, it has little capacity to stimulate cellular (Th1) immune responses, important for protection against many pathogens, nor is it useful when the antigen is peptide-based.
In the 1960s and 1970s it was speculated that aluminium was related to various neurological disorders, including Alzheimer's disease. Since then, multiple epidemiological studies have found no connection between exposure to aluminium and neurological disorders.
Ath is a city in Belgium.
The acronym ATH may also refer to:
The IATA airport code for Athens International Airport in Athens, Greece
The National Rail code for Atherstone railway station, United Kingdom
Around the Horn, an ESPN Television Show
ATH, an abbreviation for atherosclerosis
the absolute threshold of hearing, a phenomenon of psychoacoustics
ATH, Polish abbreviation for University of Bielsko-Biała (Akademia Techniczno-Humanistyczna w Bielsku-Białej)
ATH (interbank network), an interbank network in Puerto Rico and the Caribbean
A Toda Hora, a Colombian interbank network
ATH, the command to "hang up" in the Hayes command set
ATH, an abbreviation, standing for "athlete" used in American football recruiting to denote a recruit whose position on the team has not yet been determined
Alton Towers Hotel
ATH is a common name for Alumina Trihydrate, see Aluminium hydroxideActivated alumina
Activated alumina is manufactured from aluminium hydroxide by dehydroxylating it in a way that produces a highly porous material; this material can have a surface area significantly over 200 m²/g. The compound is used as a desiccant (to keep things dry by absorbing water from the air) and as a filter of fluoride, arsenic and selenium in drinking water. It is made of aluminium oxide (alumina; Al2O3). It has a very high surface-area-to-weight ratio, due to the many "tunnel like" pores that it has. Activated alumina in its phase composition can be represented only by metastable forms (gamma-Al2O3 etc.). Corundum (alpha-Al2O3), the only stable form of aluminum oxide, does not have such a chemically active surface and is not used as a sorbent.Adjuvant
An adjuvant is a pharmacological or immunological agent that modifies the effect of other agents. Adjuvants may be added to a vaccine to boost the immune response to produce more antibodies and longer-lasting immunity, thus minimizing the dose of antigen needed. Adjuvants may also be used to enhance the efficacy of a vaccine by helping to modify the immune response to particular types of immune system cells: for example, by activating T cells instead of antibody-secreting B cells depending on the purpose of the vaccine. Adjuvants are also used in the production of antibodies from immunized animals. There are different classes of adjuvants that can push immune response in different directions, but the most commonly used adjuvants include aluminum hydroxide and paraffin oil.Aloxiprin
Aloxiprin (or aluminium acetylsalicylate) is a medical drug used for the treatment of pain and inflammation associated with muscular skeletal and joint disorders.
It is used for its properties as an anti-inflammatory, antipyretic and analgesic drug.
It is a chemical compound of aluminium hydroxide and aspirin.Alum
An alum () is a type of chemical compound, usually a hydrated double sulfate salt of aluminium with the general formula XAl(SO4)2·12H2O, where X is a monovalent cation such as potassium or ammonium. By itself, "alum" often refers to potassium alum, with the formula KAl(SO4)2·12H2O. Other alums are named after the monovalent ion, such as sodium alum and ammonium alum.
The name "alum" is also used, more generally, for salts with the same formula and structure, except that aluminium is replaced by another trivalent metal ion like chromium(III), and/or sulfur is replaced by other chalcogen like selenium. The most common of these analogs is chrome alum KCr(SO4)2·12H2O.
In some industries, the name "alum" (or "papermaker's alum") is used to refer to aluminium sulfate Al2(SO4)3·nH2O. Most industrial flocculation done with "alum" actually uses aluminium sulfate. In medicine, "alum" may also refer to aluminium hydroxide gel used as a vaccine adjuvant.Aluminium carbonate
Aluminium carbonate (Al2(CO3)3), is a carbonate of aluminium. It is not well characterized; one authority says that simple carbonates of aluminium, gallium and indium are not known. Basic sodium aluminium carbonate, the mineral dawsonite, is a known compound.Aluminium chloride
Aluminium chloride (AlCl3), also known as aluminium trichloride, is the main compound of aluminium and chlorine. It is white, but samples are often contaminated with iron(III) chloride, giving it a yellow color. The solid has a low melting and boiling point. It is mainly produced and consumed in the production of aluminium metal, but large amounts are also used in other areas of the chemical industry. The compound is often cited as a Lewis acid. It is an example of an inorganic compound that reversibly changes from a polymer to a monomer at mild temperature.Aluminium hydroxide oxide
Aluminium hydroxide oxide or aluminium oxyhydroxide, AlO(OH) is found as one of two well defined crystalline phases, which are also known as the minerals boehmite and diaspore. The minerals are important constituents of the aluminium ore, bauxite.Antacid
An antacid is a substance which neutralizes stomach acidity and is used to relieve heartburn, indigestion or an upset stomach.Bauxite
Bauxite is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium. Bauxite consists mostly of the aluminium minerals gibbsite (Al(OH)3), boehmite (γ-AlO(OH)) and diaspore (α-AlO(OH)), mixed with the two iron oxides goethite and haematite, the aluminium clay mineral kaolinite and small amounts of anatase (TiO2) and ilmenite (FeTiO3 or FeO.TiO2).In 1821 the French geologist Pierre Berthier discovered bauxite near the village of Les Baux in Provence, southern France.Bayer process
The Bayer process is the principal industrial means of refining bauxite to produce alumina (aluminium oxide). Bauxite, the most important ore of aluminium, contains only 30–60% aluminium oxide (Al2O3), the rest being a mixture of silica, various iron oxides, and titanium dioxide. The aluminium oxide must be purified before it can be refined to aluminium metal.Blue Pond (Biei)
Blue Pond (青い池, Aoi-ike) is a man-made pond feature in Biei, Hokkaido, Japan. It is the result of works on the Biei River (美瑛川), carried out after the 1988 eruption of Mount Tokachi, to protect the town of Biei from volcanic mudflows. The colour is thought to result from the accidental presence of colloidal aluminium hydroxide in the water. Damage caused by Typhoon Mindulle in August 2016 resulted in a temporary drop in the water level and in the colour briefly turning brown with mud and sand from the Biei River.Carl Josef Bayer
Carl Josef Bayer (also Karl Bayer, March 4, 1847 – October 4, 1904) was an Austrian chemist who invented the Bayer process of extracting alumina from bauxite, essential to this day to the economical production of aluminium.
Bayer had been working in Saint Petersburg to develop a method to provide alumina to the textile industry that used it as a fixing agent in the dyeing of cotton. In 1887, he discovered that aluminium hydroxide precipitated from an alkaline solution which is crystalline and can be filtered and washed more easily than that precipitated from an acid medium by neutralization. In 1888, Bayer developed and patented his four-stage process of extracting alumina from bauxite ore.
In the mid-19th-century, aluminium was so precious that a bar of the metal was exhibited alongside the French Crown Jewels at the Exposition Universelle in Paris 1855. Along with the Hall-Héroult process, Bayer's solution caused the price of aluminum to drop about 80% in 1890 from what it had been in 1854.Cytoprotection
Cytoprotection is a process by which chemical compounds provide protection to cells against harmful agents.For example, a gastric cytoprotectant is any medication that combats ulcers not by reducing gastric acid but by increasing mucosal protection. Examples of gastric cytoprotective agents include prostaglandins which protect the stomach mucosa against injury by increasing gastric mucus secretion. Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit the synthesis of prostaglandins and thereby make the stomach more susceptible to injury. Gastric cytoprotective drugs include carbenoxolone, deglycyrrhizinised liquorice, sucralfate (aluminium hydroxide and sulphated sucrose), misoprostol (a prostaglandin analogue), bismuth chelate (tri-potassium di-citrato bismuthate) and zinc L-carnosine.Deville process
The Deville process was the first industrial process used to produce alumina from bauxite.
The Frenchman Henri Sainte-Claire Deville invented the process in 1859. It is sometimes called the Deville-Pechiney process.
It is based on the extraction of alumina with sodium carbonate.
The first stage is the calcination of the bauxite at 1200 °C with sodium carbonate and coke. The alumina is converted in sodium aluminate. Iron oxide remains unchanged and silica forms a polysilicate.
In the second stage sodium hydroxide solution is added, which dissolves the sodium aluminate, leaving the impurities as a solid residue. The amount of sodium hydroxide solution needed depends upon the amount of silica present in the raw material. The solution is filtered off; carbon dioxide is bubbled through the solution, causing aluminium hydroxide to precipitate, leaving a solution of sodium carbonate. The latter can be recovered and reused in the first stage.
The aluminium hydroxide is calcined to produce alumina.
The process was used in France at Salindres until 1923 and in Germany and Great Britain until the outbreak of the Second World War.It has now been replaced by the Bayer process.Euclase
Euclase is a beryllium aluminium hydroxide silicate mineral (BeAlSiO4(OH)). It crystallizes in the monoclinic crystal system and is typically massive to fibrous as well as in slender prismatic crystals. It is related to beryl (Be3Al2Si6O18) and other beryllium minerals. It is a product of the decomposition of beryl in pegmatites.Euclase crystals are noted for their blue color, ranging from very pale to dark blue. The mineral may also be colorless, white, or light green. Cleavage is perfect, parallel to the clinopinacoid, and this suggested to René Just Haüy the name euclase, from the Greek εὖ, easily, and κλάσις, fracture. The ready cleavage renders the crystals fragile with a tendency to chip, and thus detracts from its use for personal ornament. When cut it resembles certain kinds of beryl and topaz, from which it may be distinguished by its specific gravity (3.1). Its hardness (7.5) is similar to beryl (7.5 - 8), and a bit less than that of topaz (8).
It was first reported in 1792 from the Orenburg district in the southern Urals, Russia, where it is found with topaz and chrysoberyl in the gold-bearing gravels of the Sanarka (nowadays probably, Sakmara River, Mednogorsk district, Orenburgskaya Oblast'). Its type locality is Ouro Prêto, Minas Gerais, Southeast Region, Brazil, where it occurs with topaz. It is found rarely in the mica-schist of the Rauris in the Austrian Alps.Gibbsite
Gibbsite, Al(OH)3, is one of the mineral forms of aluminium hydroxide. It is often designated as γ-Al(OH)3 (but sometimes as α-Al(OH)3.). It is also sometimes called hydrargillite (or hydrargyllite).
Gibbsite is an important ore of aluminium in that it is one of three main phases that make up the rock bauxite.
Gibbsite has three named structural polymorphs or polytypes: bayerite (designated often as α-Al(OH)3, but sometimes as β-Al(OH)3), doyleite, and nordstrandite. Gibbsite and bayerite are monoclinic, whereas doyleite and nordstrandite are triclinic forms.Maalox
Maalox was a brand of antacid owned by Sanofi. Their main product was a flavored liquid containing aluminium hydroxide and magnesium hydroxide, which acts to neutralize or reduce stomach acid, for the purpose of relieving the symptoms of indigestion, heartburn, gastroesophageal reflux disease, and also stomach or duodenal ulcers. In large doses, it can act as a laxative. The trademark is owned by Novartis International AG, and was first produced commercially in 1949.
Anachronistically, ‘MAALOX’ is an abbreviation of compositional elements MAgnesium, and ALuminium, as OXides of hydrogen, in an anionic, aqueous hydroxide solution. This reacts with cationic, aqueous hydrochloride found in the gut, resulting in ion-exchange neutralisation of the acid base into water and/or salt.
Some may find certain Maalox medications, such as Maalox Multi-Action, to be a successful anti-diarrhea treatment due to the aluminium hydroxide content, which in normal situations has a tendency to result in constipation. Maalox may also be used to treat nausea and stomach cramps associated with dyspepsia, diarrhea, or constipation.Sodium aluminate
Sodium aluminate is an inorganic chemical that is used as an effective source of aluminium hydroxide for many industrial and technical applications. Pure sodium aluminate (anhydrous) is a white crystalline solid having a formula variously given as NaAlO2, NaAl(OH)4 (hydrated), Na2O·Al2O3, or Na2Al2O4. Commercial sodium aluminate is available as a solution or a solid.
Other related compounds, sometimes called sodium aluminate, prepared by reaction of Na2O and Al2O3 are Na5AlO4 which contains discrete AlO45− anions, Na7Al3O8 and Na17Al5O16 which contain complex polymeric anions, and NaAl11O17, once mistakenly believed to be β-alumina, a phase of aluminium oxide.
|Magnesium (increases motility)|
|Aluminium (decreases motility)|
|Combinations and complexes|
of aluminium, calcium and magnesium