Aliminium hydroxide

Aliminium hydroxide

1. MahparaGondal(Lecturer)
Rashid LatifCollege Of Pharmacy

2. Aluminiumhydroxide,Al(OH)₃,isfoundinnatureas
themineralgibbsiteanditsthreemuchrarer
polymorphs:bayerite,doyleiteandnordstrandite.
Aluminiumhydroxideexistinmanyforms,allbased
onthecommoncombinationofonealuminiumatom
andthreehydroxidemoleculesintodifferentcrystalline
arrangementsthatdeterminetheappearanceand
propertiesofthecompound.
Gibbsiteisthemostchemicallystableformof
aluminiumhydroxide

3. Innature,theelementaluminum
combineswithotherelementstoform
compounds.Aluminumhydroxideisa
compoundwhichiscloselyrelatedto
aluminumoxideandaluminumoxide
hydroxide,theprimarydifference
betweenthethreebeingthelossof
water.Allthreecompoundsarefound
inbauxite,theoreusedforcreating
purealuminum.Whilepurealuminum
isametal,aluminumhydroxideisa
crystal.

4. Bauxite, an aluminiumore, is the world's
main source of aluminium. It consists mostly
of the mineralsgibbsite(Al(OH)
3),
bauxite mostly present near the village of Les
Bauxin Provence, southern France.

5. It’s a odorless white powder.
Formula: Al(OH)
3
Molar mass: 78.0036g/mol
Density: 2.42g/cm³
Melting point: 300°C
Soluble in: Acid, Sulfuric acid, Alkali,
Hydrochloric acid (In Water….0.0001g/100ml)
Aluminiumhydroxide is amphoteric in nature,
i.e, it has both basic and acidic nature.

6. Decomposition Reaction
Al(OH)3 Al2O3+ H2O
When it is heated to redness, It decomposes
into water and aluminiumoxide.
Reaction with Acids
Al(OH)3+ 3HCl AlCl3+ 3H2O
The hydroxide reacts with acids readily that is
hydrochloric acid forming the water and the
aliminiumsalts.

7. Hot solution of potash alum is added slowly to a hot solution
of sodium carbonate.
The aluminiumhydroxide is precipitated and then washed
thoroughly with hot water until it is free of sulfate ions.
3NaCO3+2KAl(SO4)2+3H2O 3Na2SO4 + K2SO4 + 2 Al(OH)3 + 2CO2

8. Aluminiumhydroxideusedcommerciallyismanufacturedby
theBayerprocesswhichinvolvesdissolvingbauxiteinsodium
hydroxideattemperaturesupto270°C(518°F).Thewaste
solid,bauxitetailings,isremovedandaluminiumhydroxideis
precipitatedfromtheremainingsolutionofsodiumaluminate.
2Al+2NaOH+2H2O−>2NaAlO2+3H2
2H2O+NaAlO2(aq)−>Al(OH)3(s)+NaOH(aq

9. Aluminiumhydroxide is used as an Antacid.
Aluminiumhydroxide is preferred over other alternatives such as sodium
bicarbonatebecause 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. It reacts with excess acid in the stomach, reducing the acidity of the
stomach content,which may relieve the symptoms of heartburnor dyspepsia.
Such products can cause constipation, because the aluminum ions inhibit the
contractions of smooth musclecells in the gastrointestinal tract, slowing
peristalsisand 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 hydroxideor
magnesium carbonate, which have counterbalancing laxativeeffects.

10. Itactsasastringentandantisepticbecauseofaluminiumions
formedbyitssolutioninthehydrochloricacidofthestomach,
soalsousedasprotectiveintreatingpepticulcer.
PrecipitatedAluminiumhydroxideisincludedasanadjuvant
insomevaccines(e.g.anthraxvaccine).Sinceitabsorbs
proteinwell,italsofunctionstostabilizevaccinesby
preventingtheproteinsinthevaccinefromprecipitatingor
stickingtothewallsofthecontainerduringstorage.

11. Brand names as antacids
Alu-Cap, Aludrox, Gavisconor Pepsamar.
brands for aluminiumhydroxide
adjuvant
Alhydrogel, made by BrenntagBiosector