Question

What is meant by water of crystallization? Give examples of salts with water of crystallization, and their uses.

Answer 1

Water of crystallization is a fixed number of water molecules present in the crystal structure.

Substances in our daily use which contain salt with water of crystallization :

i) Alum (Potash alum — (K₂SO₄.Al₂(SO₄)_3.24H₂O) :

• Alum and burnt alum is used in medicines.
• In the paper industry, alum is used to give shine to the paper.
• Alum is used to stop bleeding from Wound.
• Alum is used in the process of purification of water.

 

ii) Bor (Na₂B₄O₇.1OH₂O) :

• Borax is used in the cosmetic industry to make lotions, shampoos and cold creams.
• It is used to remove the stain on clothes in a laundry;
• In the laboratory with the help of borax bead test, basic elements from the coloured salts are determined.

 

iii) Epsom salt (Magnesium sulphate MgSO₄.7H₂O):

• Epsom salt is used in the manufacture of fertilizers and also to enhance the green colour of plants and vegetables.
• It is used in the manufacture of purgative medicines.
• It is used as body scrub.
• It is added in bath water (salt bath) to relieve muscle pain.

 

iv)  Barium chloride (BaCl₂.2H₂O) :

• It is used in the purification of brine solution. (saturated sodium chloride solution).
• It is used in the waste water management.
• It is used in the paper industry and also used in the dye industry, ceramics, oil purification and pesticides.

 

v) Sodium sulphate (Glauber’s salt Na₂SO₄.10H₂O) :

• It is used in the preparation of detergents.
• It is used to make paper pulp in paper industry and also used in the dye in the dye industry.
• It is used to make mild purgatives.

 

vi) Blue vitriol (CuSO₄.5H₂O) :

• It is used in the blood test to diagnose anaemia.
• Blue vitriol and slaked lime is used in the Bordeaux mixture, which is used as a fungicide on fruits.