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The grain per gallon (gpg) is a unit of water hardness defined as 1 grain (64.8 milligrams) of calcium carbonate dissolved in 1 US gallon of water (3.785412 L). It translates into 1 part in about 58,000 parts of water or 17.1 parts per million (ppm). Also called Clark degree (in terms of an imperial gallon).
Grain per gallon (gpg) is defined as 1 grain (64.8 mg) of calcium carbonate per U.S. gallon (3.79 litres), or 17.118 ppm. 1 mmol/L is equivalent to 100.09 mg/L CaCO 3 or 40.08 mg/L Ca 2+. A degree of General Hardness (dGH or 'German degree' (°dH, deutsche Härte)) is defined as 10 mg/L CaO or 17.848 ppm.
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.
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).
A box of .38 Special (9.1 mm) cartridges that have 148-grain (9.6 g) bullets. Grains are commonly used to measure the mass of bullets and propellants. [11] [12] In archery, the grain is the standard unit used to weigh arrows. [13] In North America, the hardness of water is often measured in grains per U.S. gallon (gpg) of calcium carbonate ...
Since CaO has a molar mass of 56.08 g/mol, 1 dGH is equivalent to 0.17832 mmol per litre of elemental calcium and/or magnesium ions. In water testing hardness is often measured in parts per million (ppm), where one part per million is defined as one milligram of calcium carbonate (CaCO 3) per litre of water.
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Download QR code; Print/export Download as PDF; Printable version; In other projects Wikidata item; ... Mohs hardness [1] Vickers hardness (MPa) [1] Brinell hardness