The annual meeting of IDCNS was held 22-23 August 1996 at the Bureau International des Poids et Mesures (BIPM) in Sèvres, France. The meeting followed so closely on the conclusion of the IUCr Seattle Congress that neither the IUCr Representative nor the Alternate were able to participate. Nevertheless, the strong objections presented by the IUCr, at earlier meetings of IDCNS, to the 1994 proposal of the Comité Consultative d'Unités (CCU) of BIPM to deprecate the Ångström were set forth very effectively by the Chair of IDCNS at the April 1996 meeting of CCU. Among the resulting recommendations made by CCU to the Comité International des Poids et Mesures (CIPM) for final action on this matter was that Chapter IV (entitled Units outside the International System) in the next edition of the authoritative brochure Le Système International d'Unités (SI), to be published in 1997, should be substantially revised in a major change of style. Table 10 in this chapter will have the revised heading `Other units currently accepted for use with the SI. These units should be expressed in relation to the SI in every document in which they are used.' There will be no further deprecatory remarks. Table 10 will contain the following units: are, hectare, Ångström, bar, barn, nautical mile and knot, and will give their relation to the SI. The practical consequence of this decision is that Ångströms may continue to be used without being in breach of anything said in the SI Brochure, provided only that such authors include a footnote in every paper that makes use of Ångströms along the lines: `1 Å = 10-10 m'. The IUCr has interpreted this proviso by printing the statement `Units: The International System of Units (SI) is used in all IUCr journals except that the Ångström (symbol Å, defined as 10-10 m) is generally preferred to the nanometre (nm) or picometre (pm) as the appropriate unit of length.' in each issue of all journals.
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 that has now been signed by 48 nations.
Among other matters discussed in Sèvres of interest to the IUCr, the third edition of IUPAC's Green Book Quantities, Units and Symbols in Physical Chemistry is expected to be published in 1998. It will contain a new section on uncertainties, also new material on surface science, NMR and nonlinear spectroscopy. A further development in the consideration of prefixes for binary systems is the proposal by the International Electrotechnical Commission to adopt the following: 210 = kibi (kilobinary), symbol Ki; 220 = mebi (megabinary), symbol Mi; 230 = gibi (gigabinary), symbol Gi and 240 = tebi (terabinary), symbol Ti. Comment by crystallographers on this proposal is invited and should be sent either to the Representative or the Alternate Representative.
A total of 39 nomenclature reports originating in the Divisions and Commissions of IUPAC were received by the Representative in the course of the year. Reports containing matters likely to be of interest or concern to the IUCr were reviewed with care and corrections made where necessary. Following revision, as required by IDCNS, all accepted nomenclature reports are published in Pure Appl. Chem. and constitute the current nomenclature policy of IUPAC.