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IUCr 1995 Report - IUPAC Interdivisional Committee on Nomenclature and Symbols (IDCNS)

The annual meeting of the IDCNS was held 8-9 August 1995 in Guildford, UK. As has often been the case, it overlapped one or other major crystallographic meeting. This year, it coincided with the 16th European Crystallographic Meeting. Neither the IUCr representative, the alternate, nor several other qualified crystallographers approached were able to participate in this IDCNS meeting. However, it proved possible for IDCNS to pay adequate attention to a primary IUCr concern regarding the ångström. Our strong objections, as expressed by many of our Editors and others associated with IUCr publications, to the 1994 proposal by the Comité Consultative d'Unités (CCU) of the Bureau International des Poids et Mesures (BIPM) to deprecate the ångström were presented in advance of the meeting. The Chair of IDCNS agreed to transmit these objections to CCU. IDCNS now supports a different approach to the classification of units, in which non-SI units would simply be listed without indication of status but with an account of their usage by various communities. The Chair reported that the 1994 recommendations would be reviewed further at the CCU meeting in April 1996 before they might be submitted to the Comité International des Poids et Mesures (CIPM) for final action. Authority to act in all matters touching on the demands for higher accuracy, wider range and greater diversity in measurement standards between nations has been given jointly to the Conference 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 of interest to the IUCr, IUPAC's Green Book Quantities, Units and Symbols in Physical Chemistry is presently in revision with the aim of publishing the third edition in 1998. It will contain, inter alia, a new section on uncertainties in measurement for consistency with the recent International Organization for Standardization's Guide to the Expression of Uncertainty in Measurement. The IUCr is already in conformity with this document, see Acta Cryst. (1995), A51, 565-569. The proposal has been made to CCU that the terms kilobyte (kb) and megabyte (Mb) be used only for 103 (not 1024) and 106 (not 10242) bytes, respectively. New related prefixes have been proposed for these common units as follows: 210 = kibi (kilobinary), symbol kb; 220 = mebi (megabinary), symbol Mb; 230 = gibi (gigabinary), symbol Gb; and 240 = tebi (terabinary), symbol Tb. In consequence, the unit for 210 bytes would become kibibyte (kbbyte), that for 220 bytes mebibyte (mbbyte) etc. Symbols for the bit and the byte are under discussion. These proposals have not been accepted by CCU and alternatives are under consideration. Interested crystallographers are invited to suggest less confusing terminology for large binary quantities either to the representative or alternative representative for consideration by the CCU.

43 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 the IDCNS, all accepted nomenclature reports are published in Pure Appl. Chem. and constitute the current nomenclature policy of IUPAC.

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Updated 13th February 1997

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