An international comparison study on the accurate determination of the molar mass M(Si) of silicon artificially enriched in ²⁸Si (x(²⁸Si) > 0.9999 mol mol⁻¹) has been completed. The measurements were part of the high level CCQM-P160 pilot study assessing the ability of National Metrology Institutes (NMIs) and Designated Institutes (DIs) to make such measurements at the lowest possible levels of measurement uncertainty and to identify possible difficulties when measuring this kind of sample.

This study supports the molar mass measurements critical to disseminating the silicon route to realizing the new definitions for the kilogram and the mole. Measurements were also made by one external research institute and an external company.

The different institutes were free to choose their experimental (mass spectrometric) set-ups and equipment, thereby enabling also the comparison of different techniques. The investigated material was a chemically pure, polycrystalline silicon material. The subsequent modified single crystalline secondary product of this material was intended for the production of silicon which was used for two additional spheres in the context of the redetermination of the Avogadro constant N _A, required for the revision of the International System of Units (SI) via fundamental constants which came into force from May 2019. The CCQM pilot study was organized by Physikalisch-Technische Bundesanstalt (PTB). Aqueous silicon solutions were shipped to all participating institutions. The data analysis as well as the uncertainty modelling and calculation of the results was predefined. The participants were provided with an uncertainty budget as a GUM Workbench file as well as a free software license for the duration of the comparison. The agreement of the values of the molar mass (M(Si) = 27.976 942 577 g mol⁻¹) was excellent with ten out of 11 results reported within the range of relative uncertainty of 1 10⁻⁸ required for the revision of the SI.

关于精确测定人工富集²⁸ Si（x（²⁸ Si）> 0.9999 mol mol ^-1）的硅的摩尔质量M（Si）的国际比较研究已经完成。这些测量是CCQM-P160高级别试验研究的一部分，该试验评估了国家计量学会（NMI）和指定研究所（DI）的能力，以尽可能低的测量不确定度进行此类测量，并确定了在进行此类测量时可能遇到的困难样本。

这项研究支持摩尔质量测量，这对于传播硅路线对于实现千克和摩尔的新定义至关重要。一家外部研究机构和一家外部公司也进行了测量。

不同的研究所可以自由选择他们的实验（质谱）设置和设备，从而也可以比较不同的技术。所研究的材料是化学纯的多晶硅材料。该材料随后的改性单晶副产品用于生产硅，该硅在重新确定Avogadro常数N _A的情况下用于两个其他球体，是通过基本常量修订国际单位制（SI）的要求，该常量自2019年5月起生效。CCQM试点研究由Physikalisch-Technische Bundesanstalt（PTB）组织。水性硅溶液被运送到所有参与机构。预定义了数据分析以及不确定性建模和结果计算。作为GUM工作台，为参与者提供了不确定性预算文件以及比较期间的免费软件许可。摩尔质量（M（Si）= 27.976 942 577 g mol ^-1）的值非常一致，在11项结果中有10项报告了在SI修订所需的1 10 ^-8的相对不确定度范围内。