Question

What is the method used to remove permanent hardness in water?

Answer 1

The material used to remove permanent hardness of water is washing soda.
Other materials used are,
1. chemical process of boiling hard water
2. Calgon process
3. adding slaked lime (Clark's process)
4. using ion exchange resins
5. ion exchange process.
     
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Answer 2

The material is washing soda. Other methods are
ion exchanging process.
boiling water.