The hardness due to the presence of chloride and sulphate salts of calcium and magnesium is known as permanent hardness of water.
Removal of hardness:
1. Adding washing soda:
1. Washing soda is used to remove permanent hardness of water.
2. It converts chlorides and sulphates into insoluble carbonates.
3. These insoluble carbonates are removed by filtration.
2. Distillation:
1. Temporary and permanent hardness both can be removed by the method of distillation.
2. The water obtained after distillation is called distilled water.
3. It is the purest form of water.
