Use washing soda. (sodium carbonate)
- This precipitates out the hardness as insoluble carbonates.
Ca^2+(aq) + CO3^2-(aq) = CaCO3(s)2
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Use an ion exchange column.
- These columns contain sodium ions that are exchanged for calcuim and magnesium ions when they pass through them.
- Once all of the sodium ions are exchanges, the resin is washed with salt solution to give it more sodium ions.
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