IUCr 1994 Report - IUPAC Interdivisional Committee on Nomenclature and Symbols (IDCNS)

The Annual Meeting of IDCNS was held 26-27 August 1994 in Reading, England. The agenda contained several matters of direct interest to the IUCr, of which the principal was the `proposed deprecation' of the angström by the Comité Consultative d'Unités of the Bureau International des Poids et Mesures (BIPM). Acceptance of this change, proposed by ISO Technical Committee ISO/TC12, would result in the angström no longer being approved by BIPM for `temporary use with SI units' but categorized instead as `should be avoided for use with SI units' and replaced either by nm or pm. Motivation for the proposal came from the perceived need to improve international communication across all fields by encouraging the use of standard units and quantities; ISO/TC12 was convinced that this improvement could not be accomplished over the long run if the special names in Table 10 in the 6th edition of Le Système International d'Unités published by BIPM in 1991, all of which are associated with special fields including angström, barn, curie, röntgen, rad and rem, were continued to be recognized for use. It was noted, for example, that the rapidly growing field of nanotechnology will experience error and/or confusion with mixed units of A, nm and pm. The suggestion was made that crystallographers and structural chemists should be able to convert easily to SI units. The IUCr Representative, together with a few others but not the majority present, argued strongly for BIPM retaining the present status for the angström at least for another decade or so while we gradually introduce the nm and pm in place of the A in our journals. The consensus was that the deprecation proposal could not be postponed indefinitely.

Another item of interest was the ISO recommendation (in ISO Standard 31-0, published in 1992) to accept only the comma on the line as the SI decimal sign, with digits grouped in threes and separated only by a thin space. Most IDCNS members were unaware of this Standard, and much concern was expressed over its introduction since the majority of the world's population used the period as the decimal marker. It was agreed that, since adequate input had not been solicited in advance of issuing the Standard and the logic favouring the comma over the period was questionable, member Unions need not follow this Standard in the meantime. There was full agreement on the use of the thin space separator. A third item of interest to the IUCr was the ISO recommendation to accept both lower case `l' and upper case `L' as symbols for the litre. IDCNS agreed to this recommendation, but pointed out the possibility of confusion between the symbols 1 and l. Other matters of interest to the IUCr included recommendations that c.g.s. units with special names (erg, dyne, poise, stokes, gauss, maxwell, stilb and phot as given in Table 11) be deprecated, also that the units radian (rad) and steradian (sr) be listed with other Derived Units of SI. Liaisons between the IUCr Working Group on Phase Transitions and both IUPAP and IUPAC, see Commission on Crystallographic Nomenclature report, were appointed by the Representatives of these Unions to IDCNS. Nearly 50 nomenclature proposals originating in the Divisions and Commissions of IUPAC were viewed, and commented on where appropriate, by the Representative. All accepted proposals are published in Pure Appl. Chem.

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