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Chemistry International

The News Magazine of IUPAC

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Volume 36, Issue 4


Quo vadis—“Whither thou goest?”

Ron Weir
Published Online: 2014-07-17 | DOI: https://doi.org/10.1515/ci.2014.36.4.2

Reading historical novels frequently raises questions for me regarding the various systems of weights and measures used in past empires. The builders of the Egyptian pyramids used the “royal cubit” of length, which equalled the “length of someone’s forearm” without defining the “someone.” It is thought that one “royal cubit” was approximately equal to 52.4 cm, but how three significant figures are justified is not clear to me. However, there was also the “short cubit” in use, which was defined as the distance from the elbow to the thumb, again without defining whose elbow and thumb serve as the “reference.” When the Persian Empire encompassed Egypt, the “royal Persian cubit” was introduced and it is thought to have equalled 64.2 cm.

Subsequently the Roman legions and cavalry measured their daily marches in passus or the Roman mile that equalled 1000 passus (1480 m). Part of the Roman systems of weights and measures persisted in Europe until the French revolution in the 18th century. Prior to 1795, no unified system existed in France. During this time, the unit of length was the “King’s foot,” at least it was known which king was involved. The livre (pound) was the unit of weight, a mass that varied in size from town to town and even within the markets of a town. Shoppers and buyers could not hope to pay a fair price for goods and services.

Post 1795 in France saw the birth of the forerunner of the modern metric system. The first “standard” kg was made from platinum and adopted as the standard in 1799. The metre, litre and gram appeared with 1000 g equalling 1 kg and 1 g was equal to the weight of 1 cm3 of water. Although the temperature of the water was not specified, these developments brought some consistency and standardization. These units were to undergo refinement and in the year 1875, the Treaty of the Metre was signed in Paris. Following in 1889, the prototype of the modern 1 kg was poured as an iridium-platinum ingot in England by Johnson Matthey and that mass is now held in Paris. Subsequently Johnson Matthey has supplied prototypes to some laboratories in the world. See F.J. Smith Platinum Metals 17(2) (1973) 66-68. These developments constituted the first short steps to establishing an international convention.

The Egyptians, Persians and Romans did not have the luxury or convenience of modern day communications that lead to instant transmissions potentially reaching everywhere on earth and beyond. The growing globalization forces society to ensure that a standard system of weights, measures and associated metrology along with agreed naming of medicinal drugs is put in place. International trade, customs unions, the United Nations, and UNESCO among others depend on a basic standardized system that provides clarity, especially in areas of science, medicine, engineering, and technology.

IUPAC works to promote such clarity especially in chemical fields. Within IUPAC, it is the Interdivisional Committee on Terminology, Nomenclature and Symbols (ICTNS) that is the catalyst to drive this process. ICTNS works in collaboration with the Bureau International des Poids et Mesures (BIPM), the International Union of Pure and Applied Physics (IUPAP), and the International Union of Biochemistry and Molecular Biology (IUBMB).

Since the Treaty of the Metre was signed in 1795, the advancement of science, medicine, and technology has been nothing short of astounding and advances continue at a rapid pace. To promote clarity among the growing disciplines and sub-disciplines, IUPAC, through ICTNS, publishes a series of books, the content of which is agreed upon by hundreds of experts and workers in various fields from across the world. The books are known as a series of Colour books and denoted by the colour of the cover.

The standardized protocols for naming compounds are contained in the Red Book (Nomenclature of Inorganic Chemistry) and the Blue Book (Nomenclature of Organic Chemistry). Recommendations for the use of symbols and units are summarized in the Green Book, now in its third edition. The Gold Book defines many technical terms used in chemistry and chemically related fields. The White Book focuses on biochemistry, the Purple Book on macromolecular or polymer chemistry, the Orange Book on analytical chemistry, and the Silver Book is devoted to recommendations for clinical chemistry.

As increasing numbers of international journals together with international agencies such as UNESCO adopt the IUPAC systems for terminology, nomenclature, symbols, and units as their standard for their operations, communications are becoming less ambiguous. Such advances are critically important for human safety in medicine, pharmaceuticals, and the food industry, among others. We read of one shuttle tragedy that occurred due to an O-ring sized incorrectly over confusion using local units rather than international units. The ICTNS is working to promote some flexibility in terminology, nomenclature, symbols, and units, but with the overriding requirement to ensure clarity and accuracy. Updated Colour books are in preparation.

It is not surprising that the one kg ingot stored in Paris is gradually becoming less than 1.0000 kg, albeit a reduction only in several places to the right of the decimal point. Air trapped within the ingot when it was poured is gradually percolating from within the solid, moving to the surface and escaping. The question arises, “when is a constant not a constant?” which is a query often asked by undergraduate students in science and engineering. This naturally leads to the question Quo vadis—“Whither thou goest?” What can be done about this?

The phenomenon of a changing constant has spurred a study to consider some constants of nature as fundamental constants. These include the velocity of light, Planck’s constant, Boltzmann’s constant, among others from which, as examples, the kg and metre could be derived. These proposals are being considered by the BIPM and it will likely be a few years before all the international feedback will be received from bodies such as ICTNS, IUPAP, and IUBMB. In practical terms, if the proposals are adopted, consistency will be achieved and in everyday life for most individuals, there will be no effect. None of us needs to be concerned that our weight in kg will rise or drop since most bathroom scales cannot detect such small changes.

In retrospect, tremendous progress has been made in standardization since 1795. Sometimes change is slow to be accepted as many individuals do not like change and change can be complicated by cultural and political forces. Looking ahead, it is quite appropriate in my opinion that the 100th anniversary of IUPAC will be celebrated in Paris when the IUPAC General Assembly takes place there in 2019.

For readers of this short article, interesting perusal is provided by Professor A. Richardson, Oxford J. Archaeology 19(4) (2000) 425-437; 21(1)(2002) 93-107. He has written a number of most informative historical papers.

Ron Weir < > is emeritus Professor of Chemical Engineering at the Royal Military College of Canada. He joined IUPAC in 1988 with the then Commission I.2 on Chemical Thermodynamics. He served as its Secretary and then Chair before becoming President of Division I, Physical and Biophysical Chemistry. This was followed by his becoming Chair of the Evaluation Committee. He is currently Chair of ICTNS and serving on the IUPAC Bureau. He is also the editor of the J Chem Thermodynamics.

About the article

Published Online: 2014-07-17

Published in Print: 2014-07-01

Citation Information: Chemistry International, Volume 36, Issue 4, Pages 2–3, ISSN (Online) 1365-2192, ISSN (Print) 0193-6484, DOI: https://doi.org/10.1515/ci.2014.36.4.2.

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