The term "hard water" refers to water with an extremely high mineral concentration.
Surface water that has relatively low ion concentrations, especially low levels of calcium and magnesium ions, is referred to as soft water.
The hardness of the water can be removed using a variety of techniques.
Clark's technique for softening water:
Hard water is softened with in Clark's water softening technique (slaked lime).
Clark's reagent is Calcium Hydroxide.
Calcium hydroxide is used in Clarke's method to soften water (lime). It eliminates transient hardness. By turning bicarbonates into carbonate, it softens the water.
Slaked lime, either in solid or liquid form, is added to water using this technique. Soluble bicarbonates are changed into insoluble carbonates as a result.
In this method, a calculated amount of lime is added to hard water, it precipitates out calcium carbonate and magnesium hydroxide which can be filtered off.