Question

Only permanent hardness of water is removed by
1) Soda
2) Clark's method
3) Permutit method
4) Caustic soda method ​

Answer 1

Sodium carbonate can remove temporary and permanent hardness from water. Sodium carbonate is soluble but calcium carbonate and magnesium carbonate are insoluble.

Answer 2

permanent hardness is hardness mineral content that cannot be removed by boiling when this is the case it is usually caused by the presence of calcium cell fate and or magnesium sulphate in the water which do not precipitate out as the temperature increases.