https://studyandupdates.in/the-metallic-constituents-of-hard-water-are-%e0%a4%95%e0%a4%a0%e0%a5%8b%e0%a4%b0-%e0%a4%9c%e0%a4%b2-%e0%a4%95%e0%a5%87-%e0%a4%a7%e0%a4%be%e0%a4%a4%e0%a5%8d%e0%a4%b5%e0%a4%bf%e0%a4%95-%e0%a4%98/