1.
n. [Drilling Fluids]
One of three divalent cations that can be present in water, including calcium (Ca
+2), magnesium (Mg
+2) and ferrous (Fe
+2, a form of iron). Hardness ions develop from dissolved minerals,
bicarbonate,
carbonate, sulfate and chloride. Bicarbonate salts cause temporary hardness, which can be removed by boiling the water and leaving behind a calcium carbonate solid. Mg
+2 and Fe
+2 ions can be removed by raising the
pH (with NaOH or KOH) and then allowing the precipitated Fe(OH)
2 and Mg(OH)
2 to settle out. Calcium hardness can be removed by adding excess sodium carbonate to
precipitate Ca
+2 as CaCO
3. Hard water can be passed through an ion exchange column where hardness ions are captured on the
resin. Removal of hardness is the process called water softening.