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| DEFINITION |
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| Alum
is a series of double sulphate salts of monovalent cations and trivalent
cations containing 24 molecules of water of crystallization. |
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| GENERAL
FORMULA |
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Family
of alum can be represented by a simple formula: |
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| M2SO4.T2(SO4)3.
24H2O
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Where M = monovalent cation (Na+, K+,NH4+) T = trivalent cation (Al+3,Fe+3,Cr+3) |
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NOMENCLATURE
OF ALUM |
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| If
alum contains aluminium then it is named with monovalent cation. For example: K2SO4.Al2(SO4)3.24H2O (potash alum) If alum does not contain aluminium then it is named with trivalent cation. For example: K2SO4.Cr2(SO4)3.24H2O (chrome alum) |
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| EXAMPLES
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K2SO4.Al2(SO4)3.24H2O
(potash alum)
(NH4)2SO4.Al2(SO4)3.24H2O
(ammono
alum)
(NH4)2SO4.Fe2(SO4)3.24H2O
(ferric
alum)
K2SO4.Cr2(SO4)3.24H2O
(chrome alum) |
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| PREPARATION
OF POTASH ALUM |
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| Potash
alum is commonly known as "PHITKARI" Potash alum is prepared by mixing equi-molecular masses of potassium sulphate and aluminum sulphate in water followed by evaporation |
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| K2SO4
+ Al2(SO4)3 + 24H2O 
K2SO4.Al2(SO4)3.24H2O |
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| PROPERTIES
AND USES |
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It is white crystalline solid.
It is soluble in water.
It is used for the purification of water.
It is also used in leather industry and in paper industry.
It is used in fire extinguisher.
Melting point is 92oC |
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| PHUL
PHITKARI |
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| When potash alum is heated at 200oC it loses all molecules of water of crystallization and become a porous mass known as phul phitkari or burned alum. | ||||
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| Alum has a large molecular size and it has a property of blood clotting. Therefore, it must be used carefully in the purification of water otherwise you may suffer a great deal. | ||||
| Contact
us: info@citycollegiate.com |
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| For
latest information , free computer courses and high impact notes visit
: www.citycollegiate.com |
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