How does calcium hydroxide (hydrated lime) reduce the hardness of water?
If water hardness is caused by sulfates and chlorides of calcium and magnesium, this hardness is called permanent hardness. Water heating with permanent hardness does not reduce water hardness.
The addition of calcium hydroxide to hard water is the agent softening method. For permanent hard water, permanent hard water, calcium and magnesium ions more, adding calcium hydroxide, and magnesium ions into magnesium hydroxide, solubility is smaller, easier to remove.
If the water hardness is caused by calcium or magnesium bicarbonate, the hardness is called temporary hardness. With temporary hard water, after boiling, will produce calcium carbonate in the water calcium. The water in the series as Mr. MgCO3, continue to produce more heated water insoluble Mg (OH) 2. water hardness decreased.
