Hard water is often outlined as water that accommodates an excessive focus of calcium and magnesium ions.

Hard water is formed when water percolates by deposits of calcium and magnesium-containing rocks such as limestone, chalk and dolomite. When water percolates through such rocks , it dissolves the minerals thus producing hard water which enters the water desk.

  • when water passes by limestone, it dissolves the Calcium and therefore the hardness in water shall be due to Calcium.
  • equally when water passes by Dolomite, the Dolomite introduces Magnesium to the water.

Hardness in water is attributable to divalent cations dissolved in water like Ca2+ and Mg2+ .
These cations tend to mix with anions to type steady compounds generally known as salts.

There are two forms of water hardness, short-term and everlasting.

Temporary Hardness 

Temporary Hardness is because of the bicarbonate ion, HCO3-, being current within the water as Calcium bicarbonate – Ca(HCO3)2 and Magnesium bicarbonate – Ca(HCO3)2.

Both calcium bicarbonate and magnesium bicarbonate decompose when heated. The authentic insoluble carbonate is reformed. This occurs when water is boiled. The precipitation reactions are as follows:



As you may se boiling the water causes the precipitation of stable calcium carbonate or stable magnesium carbonate. This removes the calcium ions or magnesium ions from the water, and so removes the hardness. Therefore, hardness attributable to bicarbonates is alleged to be short-term.

Permanent Hardness 

Permanent hardness is hardness (mineral content material) that can not be eliminated by boiling. When that is the case, it’s often attributable to the presence of sulphates and chlorides of Magnesium and Calcium ( MgSo4, Mgcl2 and Caso4 and Cacl2 ) within the water, which don’t precipitate out because the temperature will increase.

Ions inflicting everlasting hardness of water may be eliminated utilizing a water softener, or ion alternate column.
Total Permanent Hardness = Calcium Hardness + Magnesium Hardness.

Measurement of Hardness of Water
Following estimates are universally recognized for checking the hardness of the water.

Classification Hardness in mg/L Hardness in ppm
Soft 0–60 less than 60
Moderately hard 61–120 60-120
Hard 121–180 120-180
Very hard ≥ 181 > 180

Seawater is taken into account to be very arduous attributable to numerous dissolved salts. Typically seawater’s hardness is within the vary of 6630 ppm. In distinction, freshwater has a hardness within the range of 15 – 375 ppm.

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