Distinguish temporaryhardness from permanent hardness of water ?

Temporary hardness of water is caused by the presence of bicarbonates of calcium and magnesium, which can be removed by boiling the water or adding lime to it. Permanent hardness of water is caused by the presence of sulfates, chlorides, and nitrates of calcium and magnesium, which cannot be removed by boiling and require the use of a water softener or ion exchange resin to remove.

Temporary Hardness

- Cause: Presence of dissolved calcium and magnesium bicarbonates (Ca(HCO3)2 and Mg(HCO3)2)
- Characteristic: Caused by dissolved salts that precipitate at elevated temperatures
- Removal: Can be removed by boiling or adding lime (calcium hydroxide) or soda ash (sodium carbonate), which convert bicarbonates to insoluble carbonates
- Temporary: Hardening minerals can be easily removed by boiling or adding lime/soda ash

Permanent Hardness

- Cause: Presence of dissolved calcium and magnesium sulfates, chlorides, or nitrates (e.g., CaSO4, MgCl2, Mg(NO3)2)
- Characteristic: Caused by dissolved salts that do not precipitate at elevated temperatures
- Removal: Difficult to remove by conventional methods (e.g., boiling, lime/soda ash treatment)
- Permanent: Hardening minerals remain dissolved and cannot be easily removed by common treatment methods
- Methods for Removal:
- Ion exchange (using ion exchange resins to exchange hardness ions with sodium or potassium ions)
- Reverse osmosis (using a semipermeable membrane to remove dissolved minerals)
- Distillation (boiling water and collecting the condensed steam to remove dissolved solids)