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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 is a white crystalline solid having a formula variously given as NaAlO 2, NaAl(OH) 4 (), [3] Na 2 O·Al 2 O 3, or Na 2 Al 2 O 4.
Al(OH) 3 is built up of double layers of hydroxyl groups with aluminium ions occupying two-thirds of the octahedral holes between the two layers. [ 5 ] [ 6 ] Four polymorphs are recognized. [ 7 ] All feature layers of octahedral aluminium hydroxide units, with hydrogen bonds between the layers.
In hot concentrated hydrochloric acid, aluminium reacts with water with evolution of hydrogen, and in aqueous sodium hydroxide or potassium hydroxide at room temperature to form aluminates—protective passivation under these conditions is negligible. [9] The reaction with aqueous alkali is often written: [2] Al + NaOH + H 2 O → NaAlO 2 ...
Aluminium oxide is an amphoteric substance, meaning it can react with both acids and bases, such as hydrofluoric acid and sodium hydroxide, acting as an acid with a base and a base with an acid, neutralising the other and producing a salt. Al 2 O 3 + 6 HF → 2 AlF 3 + 3 H 2 O Al 2 O 3 + 2 NaOH + 3 H 2 O → 2 NaAl(OH) 4 (sodium aluminate)
Aluminates are often formulated as a combination of basic oxide and aluminium oxide, for example the formula of anhydrous sodium aluminate NaAlO 2 would be shown as Na 2 O·Al 2 O 3. A number of aluminate oxyanions are known: The simplest is the approximately tetrahedral AlO 5− 4 found in the compound Na 5 AlO 4, [2] framework AlO −
The simplified leaching reaction is given by the following chemical equation: 2 Al + 2 NaOH + 6 H 2 O → 2 Na[Al(OH) 4] + 3 H 2. The formation of sodium aluminate (Na[Al(OH) 4]) requires that solutions of high concentration of sodium hydroxide be used to avoid the formation of aluminium hydroxide, which otherwise would precipitate as bayerite. [6]
corundum (Al 2 O 3) aluminium oxide hydroxides diaspore (α-AlO(OH)) boehmite or böhmite (γ-AlO(OH)) akdalaite (5Al 2 O 3 ·H 2 O) (once believed to be 4Al 2 O 3 ·H 2 O), also called tohdite; aluminium hydroxides. gibbsite (often designated as γ-Al(OH) 3, but sometimes as α-Al(OH) 3, [4] sometimes called hydrargillite or hydrargyllite)
In this reaction, sodium hydroxide acts as an agent to make the solution alkaline, which aluminium can dissolve in. 2 Al + 2 NaOH + 2 H 2 O → 2 NaAlO 2 + 3 H 2. Sodium aluminate is an inorganic chemical that is used as an effective source of aluminium hydroxide for many industrial and technical applications.