Cation

an ion with a positive electrical charge, such as calcium, magnesium and sodium.

Definitioner

Sodium: an ion found in natural water supplies, and introduced to water in the ion exchange water softening process.
Magnesium: one of the elements making up the earths crust, the compounds of which when dis-solved in water make the water hard. The presence of magnesium in water is a factor contributing to the formation of scale and insoluble soap curds.
Ion: an atom, or group of atoms which function as a unit, and has a positive or negative electrical charge, due to the gain or loss of of one or more electrons.
Calcium: one of the principal elements making up the earths crust, the compounds of which make the water hard. The presence of calcium in water is a factor contributing to the formation of scale and insoluble soap curds which are a means of clearly identifying hard water.