What Do We Measure In Moles? To the Editor: In a recent note [J. CHEM. EDUC.,59,508 (1982)l George Gorin points out that we do not have a good name for whatever it is that we measure in moles: just as we measure length in meters, time in seconds, etc., there must he something we measure in moles-the problem is to assign a suitable name to it. Professor Gorin does not like the SI phrase "amount of suhstance" and has suggested either "chemical amount" or "chemiance" for whatever-it-is-that-we-measure-in-moles. Of the various proposed names listed in Professor Gorin's note-"amount of suhstance," "psammity," "ontcount," "metromoriance," "chemiance," A d "chemical amount"none of them really "sings" - and all of them seem to miss an ohvious point. The mole is a unit of measure for the particulate nature of matter: we talk about moles because matter is composed of particles. I t seems fairly ohvious to me that the name Professor Gorin and others are seekine should he one havine "particle" as a root, and I suggestVthe word partieulalit~ Poarticularitv" is iust as sonorous. hut i t has distractine .. connotationaiechoes from the word"'particular"). Thus to talk ahout the particulal~tj.of a suhstance is to call attention tu its particulate structure-it's like talking about the "peopleness" of an army and measuring that in "platoons" or "companies" or "divisions" or whatever. T o borrow an example from Professor G r i n : we mav. sav . that 18.0 -a of H7O . has-a particulality of 1.00 moles.
Wilhelm Ostwald in 19042, just a few years after he had introduced the concept of a "mole" unit (Das Mol). At least in the mind of its originator, mole was not regarded as a "measure for the narticulate nature of matter." I t was, on the contrary, an embirical concept, which could be related in a simple way to certain physicochemical phenomena, such as the colligative properties of solutions. At the present time, the validity of the Atomic-Molecular Theory is no longer the subject of active dispute. In other words, i t is universally accepted as a basic concept for the interpretation of physicochemical phenomena. But, on the other hand, it is also true that from the operational point of view the quantity-measured-in-moles is determined and applied without explicit reference to numbers of atoms and molecules. This is nec&arilv the case.hecause these entities are too small and tw numerous to he observed directly. These considerations were very much in my mind when I proposed the name "chemical amount." The fact that this name is etymologically "neutral" with respect to theories about the nature of matter is, in my view, not a shortcoming, hut a positive virtue. George Gorln Oklahoma State University Stillwater, OK 74078
Clauslus on Entropy To the Editor: In the Fehruarv 1982 issue I read with ereat interest the abstracts of ~ r o f & o i s Campbell and Beit's presentations as well as their suhseauent dialorme. Of all the items discussed. I feel that the reference to the ~ i a u s i upapers s is of the utmmt imoortance. I am fortunate enoueh to have access to an excellent French version of the compendium published in two volumes as "The .Mechanical l'heorv of Heat." This was revised and checked by Clausius himself and i t gave me the clearest ohvsical insieht to the entropv concept. I whofehkartedly agree with ~rofessorBent that very few people read Clausius, and I would like to hope that his interest will stimulate others to do so. From the text it is quite obvious that Clausius tried to explain things for himself, because in doing so he left no stone unturned. His view of entropy, although starting from the heat engine, reaches out to what he calls "change in arrangement of the molecules in a body." Above all, the definition that Clausius gives for entropy as "transformation content" is clear and versatile enough to include the whole range of possible applications, including disorder that is covered by his "disaggregation." As a result, entropy becomes a measure of the capacity to transform, and as far as I can see. that is a rather clear ohvsical nicture. 1 wasalso very pleased to read in the~p;il1982issue that, at lone last. iustice wasdone to Ur. Horacio Uamianovich. He is oneof thes~rgentine scientists (past and present) that not onlv contribute to human knowledee hut also teach, in the hriadest meaning of the word. ~
R. J. Tykodi SDutheaStern MassachusettsUniversity Nonh DaDartmouth. MA 02747
To the Editor: I welcome Professor Tykodi's comments upon my proposal that the "auantitv-measured-in-moles" he called "chemical amount." He proposes a different name, namely .'particulality." Clearly he does not accept the premise stated in my note, that the chemical community is not disposed to accept any new, "made-up" name. He has,of course, the right to put that 6 the t e s t w e shall see. T o mykar, chemical amount "sings" a t least as sweetly as particulality; unbiased ohsewers can judge for themselves. I'rofessor Tykodi calls attention to the particulate nature of matter, afidseems to take it for granted that a name evocative of that attribute would get everybody's approval. However. that is not the case. I t is oertinent. in this connection, to recall the vigorouq dehate that took place in the period 1860-1910 roncernine the ontolorical status (jf the concents of atom and moleciel. Many scientists argued that the Atomic-Molecular Theory "was a mere hypothesis," and that it was not connected by logical necessity with "all the stoichiometric laws." The quotation is taken from the Faraday Lecture given by ~
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Maxlrno Bar611 Bmck. W. H. (Editor). "The Atomic Debates," Leicester University Press, 1967. Mswaid. W.. J. Chem. Soc., 85, 506 (1904).
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Journal of Chemical Education
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