Final Report on International comparison CCQM K23ac: Natural gas types I and III

At the highest metrological level, natural gas standards are commonly prepared gravimetrically as PSMs (primary standard mixtures). This international key comparison is a repeat of CCQM-K1e-g. The mixtures concerned contain nitrogen, carbon dioxide and the alkanes up to butane. The only difference with CCQM-K1e-g is the addition of iso-butane to the list. The results usually agree within 1% (or better) with the key comparison reference value. For ethane, nitrogen and carbon dioxide, the agreement is within 0.5% (or better), and for methane within 0.1% (or better) of the KCRV. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).