IDCNS is responsible for all recommendations concerning matters of nomenclature and symbols originating within the International Union of Pure and Applied Chemistry (IUPAC), with an emphasis on maintaining proper standards and resolving interdivisional nomenclature conflicts prior to publication in Pure Appl. Chem. The IUCr representative and his alternate evaluate each document, providing critical comment as appropriate crystallographically. IDCNS meets annually, to facilitate communications between Commissions, Divisions and International Organisations with common interests.
The meetings this triennium were held in Sèvres, France, in August 1996, in Geneva, Switzerland, in August 1997 immediately preceding the 39th IUPAC General Assembly, and in Durham, North Carolina, USA, in August 1998; the first meeting followed the Seattle Congress so closely that neither the representative nor his alternate were able to participate. Sèvres is the location of the Bureau International des Poids et Mesures (BIPM); in 1994 the Comité Consultative d'Unités (CCU) of BIPM proposed that the ångström be formally deprecated. The strong objections presented by the IUCr at earlier IDCNS meetings to this proposal were set forth so effectively by the chair of IDCNS at the April 1996 meeting of CCU that the ångström (Å) was included in Table 8, Chapter 4 of the definitive 7th edition (1998) of Le Systèm International d'Unités (SI) as "a non-SI unit currently accepted for use with the International System, although 'its use is not encouraged' ". The practical result of this decision is that the ångström continues to be in conformity with the SI provided only that it is defined in relation to the SI in every document in which it is used. IUCr journals follow this proviso by printing an appropriate statement in each issue of its journals. It is noted that authority to act in all matters between nations concerning measurement standards has been given jointly to the Conférence Générale des Poids et Mesures, the CIPM and the BIPM by the Convention du Mètre. This Convention, which dates to 1875, is a diplomatic treaty with legal consequences that is currently subscribed to by forty-eight nations.
Among IDCNS matters of interest to the IUCr is the revised list of atomic weights through atomic number 111 (symbol Uuu, name Unununium, atomic weight ~272) published in Pure Appl. Chem. (1997). 69, 24712473. Uuu and the element with atomic number 110 (symbol Uun, name Ununnilium, atomic weight ~269) are the only elements with three-letter symbols. The revised list of atomic weights for atomic numbers 1111 may be found at: http://www.chem.qmw.ac.uk/iupac/. A proposal by the International Electrotechnical Commission to adopt the following prefixes for binary systems: 210 = kibi (kilobinary), symbol Ki; 220 = mebi (megabinary), symbol Mi; 230 = gibi (gigabinary), symbol Gi; and 240 = tebi (terabinary), symbol Ti is under consideration. The class of supplementary SI units will be deleted, so that there are now only base and derived units. The proposal to extend the range of SI prefixes from the present 10±24 to 10±48 is also under consideration, and important progress has been made toward a new and fundamental definition of the kilogram. The International Standardization Organization (ISO) practice for displaying dates is to use the order year/month/day, thereby eliminating the present ambiguity between the European order day/month/year and the US order month/day/year. Both ISO and IUPAC recommend that numerical values of physical quantities in tables and figures be labelled by their international symbol divided by the SI unit; for example lambda/nm, not lambda (nm) [the IUCr would use lambda/Å, not lambda (Å)]. The reason is to allow manipulation of physical quantities, numerical values and units by the ordinary rules of algebra and to eliminate possible ambiguity by representing numerical quantities with an unambiguous dimension of unity.
All provisional and all final IUPAC nomenclature recommendations, also all IUPAC books, are in the process of becoming accessible on-line at http://www.iupac.org as IUPAC moves toward full electronic publishing.
Among recent IUPAC publications of interest to many crystallographers are Principles of Chemical Nomenclature, A Guide to IUPAC Recommendations by G.J. Leigh, H.A. Favre & W.V. Metanomski [(1998), Oxford: Blackwell], and Compendium of Chemical Terminology, IUPAC Recommendations, 2nd Edition by A.D. McNaught & A. Wilkinson [(1997), Oxford: Blackwell]. The 3rd edition of IUPAC's Green Book Quantities, Units and Symbols in Physical Chemistry, currently in preparation, will contain a new list of fundamental constant values, a new section on uncertainties, new material on surface science, NMR and non-linear spectroscopy and will be published in computer-readable format.
A major concern of IDCNS was the recent Report of the IUPAC Strategy Development and Implementation Committee (SDIC), which proposes to terminate most of the long-term Commissions of IUPAC and replace them by short-term Task Groups to carry out scientific projects. IDCNS prefers more evolutionary means for improving the less-effective Commissions to the SDIC's revolutionary proposals. V. Metanomski of Chemical Abstracts became the new Secretary of IDCNS on 1 January 1998. T. Cvitas of Zagreb will succeed I. Mills as Chair in January 2000. The IUPAC Secretariat has moved from Cambridge, UK, to Research Triangle Park, NC, USA.
S.C. Abrahams, IUCr Representative
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