Aluminium chloride


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Aluminium chloride:

  • Method of preparation of anhydrous aluminium chloride (Al2Cl6 or AlCl3)

1)  By passing dry chlorine gas over heated aluminium :

anhydrous AlCl3  is obtained.

2Al + 3Cl2 ——-> 2AlCl3

2)  By passing dry HCl in heated aluminium :

2Al + 6HCl ———-> 2AlCl3 + 3H2

3)  By passing dry chlorine gas over heated alumina and coke :

Al2O3 +3C +3Cl2 ———>  2AlCl3  + 3CO

  • Methods of preparation of hydrated aluminium chloride:

1) By dissolving aluminium in hydro chloric acid :

2Al + 6HCl ——–> 2AlCl3 + 3H2

2) By dissolving aluminium hydroxide in HCl :

AlCl3 solution is obtained which on concentration gives crystals of AlCl3

Al(OH)3 + 3HCl ———-> AlCl3 + 3H2O


1) It is colourless, crystalline solid, soluble in water.

2) Hydrolysis :

Aqueous solution of AlCl3  is acidic in nature because on hydrolysis ,it gives strong acid.

AlCl3 + 3H2O———-> Al(OH)3 + 3HCl

3) Reaction with Sodium hydroxide (NaOH) :

AlCl3 + 3NaOH ———-> Al(OH)3 + 3NaCl

Al(OH)3 + NaOH ———–> NaAlO2 + H2O

4) Reaction with Ammonium hydroxide (NH4OH) :

White precipitate of aluminium hydroxide is obtained. This precipitate do not dissolve in excess of NH4OH

AlCl3 + 3NH4OH ———> Al(OH)3 + 3NH4Cl

5) Reaction with dry ammonia (NH3 gas) : Addition  compound is obtained.

AlCl3 + 6NH3 ———-> AlCl3. 6NH3

6) Effect of heat :

On heating aluminium chloride decomposes to give Alumina, hydrochloride and water.

2AlCl3 . 6H2O ———-> Al2O3 + HCl + H2O


i) It is used as catalyst in friedel craft’s reaction.

ii) It is used as mordant in dye.

Structure of Aluminium chloride:

AlCl3 is electron deficient compound so it exists as dimer (Al2Cl6) .



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