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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).
[14] [15] Otherwise, water hardness is measured in the dimensionless unit of parts per million (ppm), numerically equivalent to concentration measured in milligrams per litre. [14] [15] One grain per U.S. gallon is approximately 17.1 ppm. [14] [note 1] Soft water contains 1–4 gpg of calcium carbonate equivalents, while hard water contains 11 ...
number symbol name Mohs hardness [1] Vickers hardness (MPa) [1] Brinell hardness (MPa) [1] Brinell hardness (MPa) [note 1] [2] 3: Li: lithium: 0.6: 5: 4: Be: beryllium: 5.5: 1670: 590–1320: 5: B: boron
0.1 × ( 12 ÷ 8 ) = 0.15 grain per dscf when corrected to a gas having a specified reference CO 2 content of 12 volume %. Notes: Although ppmv and grains per dscf have been used in the above examples, concentrations such as ppbv (i.e., parts per billion by volume), volume percent, grams per dscm and many others may also be used.
Conductivity based TDS meter in a cup of water. The two principal methods of measuring total dissolved solids are gravimetric analysis and conductivity. [4] Gravimetric methods are the most accurate and involve evaporating the liquid solvent and measuring the mass of residues left.
The Meyer hardness test is a hardness test based upon projected area of an impression. The hardness, H {\displaystyle H} , is defined as the maximum load, P max {\displaystyle P_{\text{max}}} divided by the projected area of the indent, A p {\displaystyle A_{\text{p}}} .
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. Consequently, 1 dGH corresponds to 10 ppm CaO but 17.848 ppm CaCO 3 which has a molar mass of 100.09 g/mol.
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 .