IUCr 1996 Triennial Report - IUPAC Interdivisional Committee on Nomenclature and Symbols (IDCNS)

IDCNS reviews all recommendations originating within IUPAC Commissions and Divisions that concern matters of nomenclature and symbols. Following revision and acceptance, these recommendations are published in Pure and Applied Chemistry and then become binding on all IUPAC-related publications. The IUCr representative and his alternate evaluate each document and provide critical comment as appropriate from the crystallographic point of view.

IDCNS met during the triennium in Lisbon, Portugal, in August 1993, in Reading, UK, in August 1994, and in Guildford, UK, in August 1995. The dates of two IDCNS meetings in this triennium so closely overlapped those of major crystallographic meetings that neither the representative nor his alternate were able to take part. The representative participated very actively at the Reading meeting, at which a major matter of concern to the IUCr was the 1994 proposal by the Comité Consultatif d'Unités (CCU) of the Bureau International des Poids et Mesures (BIPM) to deprecate further use of the ångström. Our strong objections at Reading to this proposal, together with those expressed later by many of our Editors and others associated with IUCr publications and presented in absentia in Guildford as well as those of other IDCNS members proved persuasive. The IDCNS Chair, who is also IUPAC representative to CCU, was able in turn to reach an agreement at the April 1996 meeting of CCU in which the new edition of the SI Brochure (the official French and English text of the BIPM document on the International System of Units) will be substantially revised in a major change of style. There will be no further deprecatory remarks on the ångström; instead, it will be regarded as a unit currently accepted for use with the SI. However, its relationship to the SI should be expressed henceforth in every document in which it is used in a footnote such as 1 Å = 10^-10m. The Å remains far from being part of the SI, and while the words `currently accepted' imply no time limit, they are intended to suggest that the CCU envisages a future time at which this unit will drop out of use since the ångström is not a self-defining unit as is the nanometre or the picometre.

8 May 1996 S. C. ABRAHAMS, Representative

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