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प्रश्न
What do you understand by permanent hardness?
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उत्तर
Permanent hardness refers to the mineral content in the water that is not possible to remove through boiling. The hardness is typically caused by the presence in water of magnesium sulfates and/or calcium sulfate that do not undergo precipitation at increased temperatures.
Therefore, permanent hardness is the sum of magnesium hardness and calcium hardness.
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