The chemical preparation and characterization of specimens for "absolute" measurements of the molar mass of an element, exemplified by silicon, for redeterminations of the Avogadro constant

The chemical steps needed to prepare specimens for "absolute" atomic-weight [(mean) relative atomic mass] determinations are outlined and discussed in detail for the atomic weight of silicon, A r (Si), as recently measured for a redetermination of the Avogadro constant. The estimated combined uncertainties arising from the chemical procedures in that A r (Si) measurement are shown to be almost equal to those from the associated mass-spectrometric measurements.