Another chemical that can be obtained from sodium chloride is Na2CO310 H2O(washing soda). You have seen above that sodium carbonate can be obtained by heating baking soda. Recrystallisation of sodium carbonate gives washing soda. It is also a basic salt. Na2-CO3+ 10 H2O J Na2CO3-10 H2O
Sodium carbonate and sodium hydrogen carbonate are useful chemicals for many industrial processes.

1)Sodium carbonate (washing soda) is used in glass, soap and paper industries.
2) It is used in the manufacture of sodium compounds such as borax.
3)Sodium carbonate can be used as a cleaning agent for domestic purposes.
4) It is used for removing permanent hardness of water.

• What does 10 H2 O signify?
• Does it make Na2 CO3 wet?
• Are the crystals of salts really dry? Let us find.

Removing water of crystallisation

Take a few crystals of copper sulphate in a dry test tube and heat the test tube.
What change did you e in the colour of the copper sulphate after heating?

• Did you notice water droplets on sides of the test tube? Where did they come from? Add 2-3 drops of water on the sample of copper sulphate obtained after heating.
• What do you observe? Is the blue colour of copper sulphate restored?