1. School Name
Chemistry Project
Preparation of Potash Alum
K2SO4.Al2(SO4)3. 24H2O
from scrap Aluminium(Al)
Made By:
Class: Roll no.:
Guided By:
Student’s Name
Teacher’s Name
____ __
2. CERTIFICATE
This is to certify that STUDENT’S
NAME, a student of class __ has
successfully completed this project
regarding the Preparation of Potash
Alum from scrap Aluminium under
the guidance of TEACHER’S NAME
during the year 2023-24 as per the
guidance of CBSE.
Signature of
Chemistry Teacher
Signature of
Principal
3. ACKNOWLEDGEMENT
I am grateful to god for bringing this project
to a success. I would also like to extend my
gratitude towards my Chemistry teacher
Mr Partha Sarathi Sahu for all his teachings
and guidance. I would also like to thank my
family and friends for their support and
encouragement during the making of this
project.
CONTENTS
Introduction to Alums
Aim of the experiment and
Apparatus required
Theory and Reactions Involved
Procedure and Precautions
Conclusion and Bibliography
4. Introduction to ALUMS
Alums are hydrated double sulphate salts of
Aluminium. In everyday use, they are referred
to as ‘fitkari’. These are usually produced by
combining Aluminium sulphate [Al2(SO4)3]
and the sulphate monovalent cation. Potash
alum is made by dissolving Aluminium
Sulphate and Potassium Sulphate [K2SO4] in
water.
Properties of Alum:
Astringent and acidic taste.
Highly soluble in water.
Generally exists in the form of a white
and transparent crystalline form.
Boiling point is around 200°C.
Melting point is 92.5°C.
Density is 1.725 g/cm3.
General Formula:
M2SO4.T2(SO4)3.24H2O
M: Monovalent Cation T: Trivalent Cation
5. Uses of Alum:
Baking and pickling process.
In tanning process of leather.
Coagulation and flocculation process of
water treatment.
Acidulating agent in cooking.
Drying agent in textile industry.
Acidic component of baking powder.
An antiseptic agent and adjuvant in
vaccines.
An ingredient in some toothpaste.
Used in the gargling process to reduce
teeth gum inflammation and pain.
Some common examples of Alums
Potash Alum:
Soda Alum:
Ammonium Alum:
Chrome Alum:
Selenate Alum
1.
2.
3.
4.
5.
KAl(SO₄)₂·12H₂O
NaAl(SO₄)₂·12H₂O
NH3Al(SO4)2·12H2O
KCr(SO4)2·12H2O
Al2O12Se3
6. Aim of Experiment
To prepare Potash ALum from scrap Aluminium
Apparatus required:
Scrap Aluminium (Al)
4M Potassium Hydroxide (KOH)
6M Sulphuric Acid (H2SO4)
Funnel, Beaker, Flask
Aluminum metal is treated with hot aqueous
KOH solution. Aluminium dissolves as
potassium aluminate, KAl(OH)4, salt.
2Al(s) + 2K0H(aq) + 6H2O(l) ---> 2KAl(0H)4(aq)
+3H2
Potassium aluminate solution on treatment
with dil. Sulphuric acid first gives precipitate
Al(OH)3 which dissolves on the addition of
small excess of H2SO4 and heating.
2K0H(aq) + H2SO4(aq) ---> 2Al(OH)3(s)
+ K2SO4(aq) + 2H2O(l)
Theory:
7. 2Al(0H)3(s) + 3H2SO4(aq)
---> Al2(SO4)3(aq) +6H2O(l)
The resulting solution is concentrated to near
saturation and cooled. On cooling crystals of
potash alum crystallize out.
K2SO4(aq) +Al2(SO4)3(aq) +24H2O(l)
---> K2SO4.Al2(SO4)3.24H20(s)
Reactions:
2Al(s) + 2KOH(aq) + 6H2O(l)
K2SO4(aq) + Al2(SO4)3(aq) + 24H2O(l)
2Al(OH)3 (s) + 3 H2SO4(aq)
2KOH(aq) + H2SO4(aq)
K2SO4(aq) + Al2(SO4)3(aq) + 24H2O(l)
---> 2KAl(OH)4 (aq) + 3H2
---> K2SO4.Al2(SO4)3. 24H2O(s)
---> Al2(SO4)3(aq) + 6H2O(l)
---> 2Al(OH)3 (s) + K2SO4(aq) + 2H2O(l)
---> K2SO4.Al2(SO4)3. 24H2O(s)
8. Procedure:
Take the Aluminium scraps in a conical
flask and add 4M KOH to it.
Heat the flask to facilitate the reaction
(This is a vigorous reaction that liberates
hydrogen gas and hence should be
performed carefully.)
Let the solution cool down and filter out
the impurities.
Add 6M H2SO4 to the mix which will lead
to the formation of white precipitate.
Boil the solution.
Let it cool down and after some time
crystals of Potash alum will begin to
appear.
Precautions:
To prevent hydrolysis of aluminium
sulphate, dilute sulphuric acid should be
added while preparing the saturated
solution.
9. During crystallization do not disturb the
solution.
For dissolving salts always use warm
water.
The concentrated solution should be
cooled slowly.
Conclusion
Crystals of Potash Alum (Fitkari) can be
successfully prepared using scrap
aluminium, KOH and H2SO4.
Bibliography
byjus.com
wikipedia.com
NCERT book
slideshare.net
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