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Water Chemistry

Hardness*

Definition: Hardness is a measure of the mineral, calcium and magnesium, content of the water. These ions enter a water supply by leaching from minerals within an aquifer. Common calcium-containing minerals are calcite and gypsum. A common magnesium mineral is dolomite (which also contains calcium). Rainwater and distilled water are soft, because they contain few ions.

Ideal range: Ideal calcium hardness content is 300 to 400 ppm as measured by a suitable kit.

 

Method of measurement: Hardness is most commonly measured by titration with an EDTA solution. A titration involves adding small amounts of a solution to a water sample until the sample changes color. You can titrate a sample for total hardness using a buret or hard water test kit. You can also measure calcium hardness separately from magnesium hardness by adjusting the pH and using different indicators.

 

Method of control: Lowering hardness, expressed carbonate hardness, is commonly carried out by a water softener, which is a form of chemical filtration employing an ion-exchange resin. The resin binds with mineral ions (Ca) reducing the hardness hence the mineral content of the water. The downside is that the salts used to un-bind to the minerals are back-flushed into the sewer system and pollute the environment. Another hardness control alternative is electro-chemical oxidation whereby the calcium is converted to the soft bicarbonate form, subsequently the heat point required to precipitate calcium in the carbonate form is increased substantially. 

We're eager to respond to any inquiries re: water chemistry: just hit the 'contact us' button to send us your questions.