Hard And Soft Water: Water that does not form an immediate lather with soap is called hard water. The hardness of water is due to the presence of soluble calcium, magnesium, or iron compounds. The most common compounds are calcium bicarbonate Ca(HCO3)2, magnesium bicarbonate Mg(HCO3)2, calcium sulfate CaSO4 and magnesium sulfate MgSO4. The addition of