Ten reasons NOT to fix the numerical value of the Avogadro constant

This discussion paper, circulated in advance of the 17th meeting of the Consultative Committee for Amount of Substance, addresses the proposed redefinition of the mole in terms of a fixed numerical value for the Avogadro constant. It gives ten reasons why the Avogadro constant should not be given a fixed numerical value in the International System of Units, noting that there would be no metrological benefit from such a change, and that the proposed redefinition would be more conceptually complex that the current one and divorced from practical measurement and historical background. As the conditions for redefinition of the kilogram have not been met, and no mise en pratique has been produced for the proposed new definition, the paper concludes that the proposal should be rejected.