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  2. Grain per gallon - Wikipedia

    en.wikipedia.org/wiki/Grain_per_gallon

    Water chemists measure water impurities in parts per million (ppm). For understandability, hardness ordinarily is expressed in grains of hardness per gallon of water (gpg). The two systems can be converted mathematically.

  3. dKH - Wikipedia

    en.wikipedia.org/wiki/DKH

    As a unit 1 dKH is the same as 1 °dH which is equal to approximately 0.1786 mmol/L or 10.02 milligrams (mg) of calcium carbonate per litre of water, i.e. 17.86 ppm. [ citation needed ]

  4. dGH - Wikipedia

    en.wikipedia.org/wiki/DGH

    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.

  5. Stiff diagram - Wikipedia

    en.wikipedia.org/wiki/Stiff_diagram

    A Stiff diagram, or Stiff pattern, is a graphical representation of chemical analyses, first developed by H.A. Stiff in 1951.It is widely used by hydrogeologists and geochemists to display the major ion composition of a water sample.

  6. Gibbs–Helmholtz equation - Wikipedia

    en.wikipedia.org/wiki/Gibbs–Helmholtz_equation

    The definition of the Gibbs function is = + where H is the enthalpy defined by: = +. Taking differentials of each definition to find dH and dG, then using the fundamental thermodynamic relation (always true for reversible or irreversible processes): = where S is the entropy, V is volume, (minus sign due to reversibility, in which dU = 0: work other than pressure-volume may be done and is equal ...

  7. Abundance of elements in Earth's crust - Wikipedia

    en.wikipedia.org/wiki/Abundance_of_elements_in...

    The abundance of elements in Earth's crust is shown in tabulated form with the estimated crustal abundance for each chemical element shown as mg/kg, or parts per million (ppm) by mass (10,000 ppm = 1%).

  8. Clarke number - Wikipedia

    en.wikipedia.org/wiki/Clarke_number

    If the concentration of a commodity in an ore X is [ppm], and the "clarke" of that commodity is [ppm], then "the clarke of concentration" of that commodity X is = (dimensionless). The value represents the degree to which the commodity is concentrated from crustal abundances to the ore by natural geochemical processes; a clue for whether the ...

  9. Standard temperature and pressure - Wikipedia

    en.wikipedia.org/wiki/Standard_temperature_and...

    In chemistry, IUPAC changed its definition of standard temperature and pressure in 1982: [1] [2] Until 1982, STP was defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 1 atm (101.325 kPa).