Resolution 2 of the 18th CGPM

Study of the surface condition of mass standards

The 18th Conférence Générale des Poids et Mesures


  • that long-term stability is one of the essential characteristics of mass standards,
  • that improvements in balances now allow variations in mass of only a few micrograms in a kilogram to be observed,
  • that variations of this order have been observed and have been attributed to surface effects due in particular to atmospheric agents,
  • that present methods of cleaning the surfaces of mass standards may have unsuspected effects,
  • that a wide range of methods now exist for the study of the surfaces of alloys used in mass standards,
  • that important results have already been obtained using these methods for the study of the surface contamination of mass standards,

recommends that laboratories apply the wide range of techniques now available for the study of surface composition and behaviour to platinum/10% iridium and other alloys used in mass standards.

reference The reader should note that the official version of this Resolution is the French text

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