The objective of this task is to provide a Technical Report containing a critical review of the definitions for the quantity amount of substance and its unit, mole, as well as the related unit of the quantity mass.
The work will consist on the compilation of existing published work related to the definition of the quantity amount of substance, its unit, and the consequence of these definitions on the unit of the quantity mass. The compilation will be reviewed critically with the aim of assembling all possible elements such as to enable to judge on the adequateness of the existing definitions or new proposals. Compilation and critical review shall rely on the broadest spectrum of interested IUPAC members. Therefore, all divisions will be offered to participate at the project, as well as ICTNS and CCE. All task group members will have a mandate to speak on behalf or their corresponding communities. External experts will be consulted.
The task group is timely scheduled with discussions in CCQM and BIPM on the new definition of the mole. A time horizon of 2015 for establishing a firm position of IUPAC with regard to this question is adequate for further decisions to be taken by CCQM, CIPM, and CGPM.
June 2014 update – The task group initiated a survey to collect opinions and comments by the IUPAC National Adhering Organizations (NAOs). The questionnaire focuses on the current definition of the mole, the new definition of the mole, the current definition of the quantity amount of substance, and the current name of the quantity amount of substance.
Because of external time-constraints, IUPAC NAOs are asked to reply no later than 1 October 2014. See questionnaire [pdf file – 90KB]. All comments will be used towards formulating the IUPAC Technical Report. Those organizations who will reply will be sent an advance draft of the IUPAC Technical Report for further comment and input before submission to Pure and Applied Chemistry.
Oct 2014 update – the task group met 25-28 July 2014; the minutes of that meeting are enclosed [pdf file-164 KB].
It was agreed that the technical report will reflect the structure of the open letter sent to all IUPAC NAOs. The following outline was agreed:
- Historical introduction
- New SI which will outline the recent proposals to change the SI
- Review of the literature with categories of published manuscripts
- Critical evaluation of the literature
- Questionnaire and the results
The task group has 68 manuscripts at its disposal dating from 1961 to 2014. All manuscripts were assigned among the members for detailed inspection and to be examined before the next meeting and which will take place in Ottawa (Canada) in January/February 2015.
July 2015 update – the task group met 29-31 January 2015; the minutes of that meeting are enclosed [pdf file-6 MB].
Ultimately the Task Group approved the proposed definition of the mole as it appears in the Draft 9th SI Brochure (16 Dec 2013)* only ‘in principle’ because several additions are warranted. First, the Task Group members agreed to recommend changing the quantity name “amount of substance” to “chemical amount”. In addition, the Task Group drafted an informative paragraph explaining the nature of the quantity which is currently known by the name “amount of substance” and its relationship with the Avogadro number, the Avogadro constant, and the number of entities. This informative paragraph will be sent to the drafting committee working on the 9th edition of the SI Brochure in order to better complement the normative definition of the mole.
Feb 2017 update – The provisional recommendation titled “Definition of the mole” is available for public review till 30 June 2017. A separate technical report titled “A critical review of the proposed definitions of fundamental chemical quantities and their impact on chemical communities” is simultaneously being prepared.
June 2017 update – The Technical Report “A critical review of the proposed definitions of fundamental chemical quantities and their impact on chemical communities (IUPAC Technical Report)” is available AOP published online 13 June 2017: https://doi.org/10.1515/pac-2016-0808; ref Pure and Applied Chemistry 89(7), pp. 951-981 (2017).
Jan 2018 update – The “Definition of the mole (IUPAC Recommendation 2017)” is published online 8 Jan 2018: https://doi.org/10.1515/pac-2017-0106; Pure and Applied Chemistry 90(1), pp. 175–180 (2018).
See announcement released 8 Jan 2018.
See CI Apr 2018 for Reactions/comments to the new definition, by Peter W. Atkins and by Bob Bucat <https://doi.org/10.1515/ci-2018-0222>
Last update 2 May 2018