IU14. IUPAC Interdivisional Committee on Nomenclature and Symbols (ICTNS)

2005 REPORT TO INTERNATIONAL UNION OF PURE & APPLIED PHYSICS (IUPAP) BY ITS REPRESENTATIVE ON Interdivisional Committee on Terminology, Nomenclature and Symbols (ICTNS)[1] 



In questions of terminology, nomenclature and symbols and the work of the ICTNS, it is the IUPAP Commission C2 SUNAMCO which acts as a link with pure and applied physicists in IUPAP and elsewhere.


The IUPAP Commission C2: Symbols, Units, Nomenclature, Atomic Masses & Fundamental Constants (SUNAMCO) [] has namely amongst its mandates to promote the exchange of information and views among the members of the international scientific community in the general field of Fundamental Constants including:


(a)  physical measurements

(b)  pure and applied metrology

(c)  nomenclature and symbols for physical quantities and units;

(d)  encouragement of work contributing towards improved recommended values of atomic masses and fundamental physical constants and facilitation of their adoption.


In reporting ICTNS activities to IUPAP, the following items are of particular interest to SUNAMCO:

Update on status of ‘color’ books

 The IUPAP ‘Red’ book SUNAMCO 87-1 “Symbols, Units, Nomenclature and Fundamental Constants in Physics, is by all accounts still popular 18 years after publication of the latest edition. A revision, perhaps with an electronic publication, is needed however. A number of other organisations such as IUPAC are also quite active in producing a number of guidance documents and books, such as the latter’s ‘green ‘ and ‘orange’ books. Some of these, for instance the ‘orange’ book[2] “Compendium on Analytical Nomenclature” have certain sections which directly overlap the contents of the IUPAP ‘Red’ book, such as accounts of the SI and tables of values of the fundamental constants and are already published on the Internet.  It is natural therefore that some amount of coordination would be in order is SUNAMCO is to go ahead with a new edition of the red book. SUNAMCO has already suggested and has had a positive response from IUPAC (both ICTNS and the Analytical Chemistry Division). SUNAMCO members expressed the wish to publish a revised red book, identifying clearly the physics part as distinct from chemistry and other engineering disciplines. While electronic versions are desirable, it was felt there was still a need for paper versions and for translations.

Redefinition of the kilogram and Proposal concerning the dalton

 The SUNAMCO Committee has debated the questions raised by the ICTNS (and corresponding discussions in the CCU, for instance) since the New Year 2005, particularly concerning units of mass and amount of substance. IUPAP has formulated its own recommendation about the possible redefinition of the kilogram. The IUPAP draft recommendation was presented amongst others at the June 2005 meeting of the CCU. Individual SUNAMCO members have also participated in related discussions of this issue in a number of fora, including within the Metre Convention, for instance, the Consultative Committees for Mass (CCM) for Electricity & Magnetism (CCEM) as well as CODATA.


In earlier discussions about the dalton at the last ICTNS meeting, the IUPAP SUNAMCO Chairman (Dr Sharma) had noted that an earlier recommendation in this field, concerning the adoption (10th General Assembly of the I.U.P.A.P. in 1960) of the exact number 12 as the relative nuclidic mass of the carbon isotope of mass number 12, had been made jointly with IUPAC, and it would perhaps be fitting to co-ordinate similarly the current proposal about the dalton.

In the meantime, IUPAP SUNAMCO C2 has made a recommendation and a resolution has been passed by IUPAP council regarding the interim approval to use both the dalton and the unified atomic mass unit for a period of time, as follows:


IUPAP C2 SUNAMCO     Resolution 15/Oct/2003

A suggestion has been made in the CCU (communicated to C2 through Brian Petley), that the time has come to replace the name and symbol of the unified atomic mass unit, u, with dalton, Da. The grounds are that the current name is a mouthful and the need to emphasize the concept of "unified" is long gone. The dalton is widely used in chemical mass spectrometry community (e.g. bio-chemistry). Its use will also bring the polymer chemists into the SI community. There is possible confusion with the astronomical unit ua, and people want to use u or U to denote the unit one. There was considerable comment on this matter from many of the SUNAMCO members. In the short term the proposed change simply endorses the present reality that both the atomic mass unit and Dalton are in use.

IUPAP should endorse the use of both names, dalton (Da) and unified atomic mass unit (u) for the atomic mass unit and strongly recommends waiting for an extended period to see which physicists and others prefer to use before making any further decisions.


Other SUNAMCO activities relevant to ICTNS

A number of contacts between IUPAC and IUPAP SUNAMCO have occurred during the period of this report. Amongst others, SUNAMCO was kindly invited by IUPAC Analytical Chemistry Division[3] to its meeting (040217, IAEA, Vienna) to discuss increased collaboration. Items discussed included:

  • cooperation about terminology (initial contacts have been made with David Moore (Los Alamos) who is active in producing the latest Orange book)
  • a possible joint project about Metrological Traceability. A proposal to ICSU entitled “Measurement Traceability – A Fair Basis For Trade” lead by IUPAC, together with IUPAP and UNIDO did not unfortunately get a positive response.
  • presentation of a talk at a Minisymposium “Emerging issues in Metrology in Chemistry”[4].


Dr Leslie R Pendrill


IUPAP C2 SUNAMCO Secretary[5]


SP Swedish National Testing & Research Institute, Measurement Technology

Box 857, S-501 15 BORÅS, Sweden, Tel: +46 (0)33 165444, Fax: +46 (0)33 165620,


[1] IUPAC Interdivisional Committee on Terminology, Nomenclature and Symbols (ICTNS),

[4]; Pendrill L R 2005 "Meeting future needs for Metrological Traceability – A physicist’s view", Accred. Qual. Assur., 10, no 3, 133 - 9

Contact IUPAP   |   Search IUPAP   |   IUPAP Home