ACS – DAY 1: Goodbye Mole

Paul Karol

In a talk titled Kilogram and mole: Definitions, standards and artifacts given today at the ACS national conference, Paul Karol argued passionately for the removal of the mole from the base set of units from the International System of Units. As it currently stands there are 7 base units: meter, kilogram, second, ampere, kelvin, candela, and mole.

The crux of his argument is that all basic physical quantities are defined as a numerical value times a unit. While a mole is just a numerical value, and has as much physical meaning as the term dozen. Karol’s arguments might have some validity but it will probably tick off many chemists who tirelessly lobbied for the mole’s inclusion to the SI base units in the ’70s.

His proposal could be to the chemistry community what the International Astronomical Union’s demotion of Pluto’s planet status did to the astronomy community. Anyone up for making shirts saying, “moles are units!”



  1. Just get rid of all of them except one.

    Seriously, it can be done. For example, let’s say we’ll keep the second. The meter can be eliminated because it is the distance that light in a vacuum travels in 1/(3*10^8) seconds. The kilogram can be defined as the amount of a certain material in a certain volume (which can now be defined using distance), ditto for the mole, amps are defined in terms of the electric charge on a mole of electrons moving through a point within a second – no need for more base units with that, a candela is defined in terms of watts/steradian at a given frequency – we’ve got that covered since watts are mass * velocity-squared/time, and the Kelvin can be defined in terms of the Boltzman constant (1.38 x 10^23 J/K).

    There. Happy? No more conflicts between the various definitions, and we can ditch that Pt/Ir block in France. It would be a great door stop for Paul.

  2. I would buy that t-shirt. Seriously.

  3. From what I can gather he is not calling for it to be abolished and not used. That would be fucking stupid, it is a very useful number.

    What he is saying it should be removed from the SI base units. It doesn’t need to be there. The mole is derived from the kilogram. The mole should be included in the derived units along with Newtons, Joules, Watts, Hertz and Volts.

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