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  2. Hardness comparison - Wikipedia

    en.wikipedia.org/wiki/Hardness_comparison

    A variety of hardness-testing methods are available, including the Vickers, Brinell, Rockwell, Meyer and Leeb tests. Although it is impossible in many cases to give an exact conversion, it is possible to give an approximate material-specific comparison table for steels.

  3. Carbonate hardness - Wikipedia

    en.wikipedia.org/wiki/Carbonate_hardness

    Carbonate hardness, is a measure of the water hardness caused by the presence of carbonate (CO 2− 3) and bicarbonate (HCO − 3) anions. Carbonate hardness is usually expressed either in degrees KH (from the German "Karbonathärte"), or in parts per million calcium carbonate ( ppm CaCO 3 or grams CaCO 3 per litre|mg/L).

  4. Hard water - Wikipedia

    en.wikipedia.org/wiki/Hard_water

    The total water hardness is the sum of the molar concentrations of Ca 2+ and Mg 2+, in mol/L or mmol/L units. Although water hardness usually measures only the total concentrations of calcium and magnesium (the two most prevalent divalent metal ions), iron, aluminium, and manganese are also present at

  5. Hardness scales - Wikipedia

    en.wikipedia.org/wiki/Hardness_scales

    Hardness scales may also refer to: Methods of measuring the deposit formation by hard water. The scale of Pencil hardness This page was last edited on 11 ...

  6. dGH - Wikipedia

    en.wikipedia.org/wiki/DGH

    Degrees of general hardness (dGH or °GH) is a unit of water hardness, specifically of general hardness. General hardness is a measure of the concentration of divalent metal ions such as calcium (Ca 2+) and magnesium (Mg 2+) per volume of water. Specifically, 1 dGH is defined as 10 milligrams (mg) of calcium oxide (CaO) per litre of

  7. Vickers hardness test - Wikipedia

    en.wikipedia.org/wiki/Vickers_hardness_test

    The Vickers test can be used for all metals and has one of the widest scales among hardness tests. The unit of hardness given by the test is known as the Vickers Pyramid Number (HV) or Diamond Pyramid Hardness (DPH). The hardness number can be converted into units of pascals, but should not be confused with pressure, which uses the same units ...

  8. Properties of water - Wikipedia

    en.wikipedia.org/wiki/Properties_of_water

    Water is the chemical substance with chemical formula H 2 O; one molecule of water has two hydrogen atoms covalently bonded to a single oxygen atom. [26] Water is a tasteless, odorless liquid at ambient temperature and pressure. Liquid water has weak absorption bands at wavelengths of around 750 nm which cause it to appear to have a blue color. [4]

  9. Water - Wikipedia

    en.wikipedia.org/wiki/Water

    Water hardness is also a critical factor in food processing and may be altered or treated by using a chemical ion exchange system. It can dramatically affect the quality of a product, as well as playing a role in sanitation. Water hardness is classified based on concentration of calcium carbonate the water contains.