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Chemical Education Today
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Letters
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The Kilogram and the Mole Redux
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Paul J. Karol
Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213
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February 2005
Vol. 82 No. 2
p. 212
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Freeman’s reply (1) to my letter (2) on the kilogram and the mole misses the point, perhaps because I was not sufficiently clear. Of his substantive criticisms, Freeman first states (correctly) I define NA—Avogadro’s number—and that I then define the kilogram (incorrect). Defining NA in conjunction with the existing undebatable definition of a mass scale based on 12C mandates, ipso facto, the kilogram metric. These are not incompatible statements which Freeman seems to interpret them to be (and, in contrast, the subsequent letter by Cvitaš recognizes as legitimate). Freeman furthermore obsesses over the artificial need to count NA atoms, ignoring first of all, the major advances in ion beam technology and associated fast electronics which enable counting rates many, many orders of magnitude larger than he envisioned, and secondly, that the choice of how much to count governs the precision of the measurement. After all, one does not stretch out an infinitely precise tape measure 299,792,458 meters in order to time the second.
Cvitaš’s somewhat hostile comment (3) seems more to agree with me than not, even stating “we could do without amount of substance and the mole”, but takes a surprisingly defensive view that, until counting atoms can be done, no one should decide “what number of which atoms should be used to define the kilogram”. That he did not recognize that the integer for NA specified in my suggestion was chosen to be both consistent with current precision and also divisible exactly by 12 is my lapse in anticipation. Nevertheless, Cvitaš reveals his territorial bias by asserting “this Journal is not a journal for discussing metrological problems encountered in precise definitions of units”. Cvitaš serves on IUPAC’s
Interdivisional Committee on Terminology, Nomenclature and Symbols (ICTNS), an
appointment that was not noted in his comment despite its relevance to the issue.
But, readers should know that the ICTNS is a group that has had its historical
share of controversial decisions. My food-for-thought letter was meant to be
stimulating, provocative, and perhaps constructive. It is not for Cvitaš to tell
this Journal what it may or may not undertake that is of interest to its readership.
Literature Cited
- Freeman, R. D. J. Chem. Educ. 2004, 80, 800.
- Karol, P. J. J. Chem. Educ. 2004, 80, 800.
- Cvitaš, T. J. Chem. Educ. 2004, 80, 801.
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| More Information |
 Citation |
Karol, Paul J. J. Chem. Educ. 2005 82 212.
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History |
Created:
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January 4, 2005
January 12, 2005
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