Abstract. One of the routes to a redefinition of the kilogram requires a new determination of the Avogadro constant at a high level of accuracy. Laboratories must achieve mass comparison between a 1 kg ²⁸Si sphere and 1 kg Pt/Ir mass standards to a combined standard uncertainty of 4 µg. The BIPM has developed a method of achieving this target. The goal of this paper is to report the advances at the BIPM and to describe our new method for linking weighings in air and in vacuum. The results obtained by classical comparisons in air are compared to those obtained by the new BIPM method.

Keywords: mass calibration, Avogadro constant, silicon sphere

^* This paper is based on work published in Metrologia 43 (2006) 46–52.

Print publication: Issue 10 (October 2006)
Received 1 February 2006, in final form 23 May 2006
Published 25 August 2006