Philadelphia 2008 ACS Council Report

July 3, 2008

The ACS Committee on Nomenclature, Terminology and Symbols (NOM) sponsored a successful symposium on Sunday, April 6, on the "Past, Present and Future of the Kilogram". This symposium was co-sponsored by the Division of Chemical Information and the Division of the History of Chemistry. Attendance was quite good and the hoped-for audience participation was thoughtful and stimulating. The result is that new recommendations on the kilogram, Avogadro's number and the ampere will likely be made to the ACS and textbook publishers in particular.

The purpose of the symposium of four invited papers was to call attention to the proposed revision of the fundamental unit, the kilogram, that has been under serious debate with the metrology community and the International Bureau of Weights and Measures (BIPM) and to encourage feedback from the chemistry community. The kilogram unit directly affects other units in chemistry such as Avogadro's number and the ampere. Two particular pending proposals were debated. One, that Avogadro's constant should be redefined as an integer. The other was how to decide between several choices on the redefinition of the kilogram.

On the Avogadro constant proposal, agreement seemed to be unanimous and is a simple idea consistent with what is practiced already in many introductory textbooks. The ACS NOM committee will construct a formal proposal in that regard. The kilogram proposal was much more contentious. Although the BIPM representative empathized with the straightforward plan of proceeding with use of 12 grams of carbon-12 being the mass of Avogadro's number of atoms, that option would oblige a loss of precision for other constants. More importantly, it was clear that the choice would continue to force an actual disconnect between the SI unit system and precise measurements in the quantum-electronic domain. This was illustrated clearly by reviewing state-of-the-art measurements being conducted at NIST. Preference is rather to define Planck's constant exactly and use ever-improving measurements to improve the mass scale beyond the parts per billion precision of today. The ACS NOM committee will reconsider its position on the kilogram and augment the Avogadro's number proposal to accommodate the BIPM proposition. It is believed at this time that changes from current values would not affect the majority of applications of interest to the chemistry community.

In other business, the committee assessed its activities against the ACS Strategic Plan forming sub-committees with specific goals. Among these goals are the communication of results and conclusions fostered by the kilogram symposium; collaborative planning for a nanotechnology terminology presentation in Salt Lake City, Spring, 2009; close communication with the CHED to further community education on nomenclature topics of interest; and a directory of nomenclature generation software.