o A m3 is Bigger than a Breadbox
T h i s isn't t h e most propitious time t o sound a discordant note a h o u t SI1units, when t h e scientific a n d industrial communities are working together to sell t h e metric system to t h e public. W e foot-draggers have more t h a n a mild suspicion t h a t t h e SI proponents are taking advantage of t h e metric conversion climate t o push their cause. As a measure of their commitment t o conformity, we should consider t h e Biblical quotation offered b y M. L. McGlashan2 Divers weights and divers measures, hoth of them are alike an abbmination to the Lord, Prouerbs XX:10. T h e response of chemists, however, has been admitted b y such fervent SI proponents a s W. G. Davies, J. W. Moore a n d R. W. Collins3 t o h e
.. . less than lukewarm. , ~t h e preface t o t h e recent edition of his A. W. A d a m ~ o n in textbook, stated bluntly Nor have I accepted the awkward SI system of units-a system in no way designed to be either convenient or relevant to physical ehemistry. First off, t h e S I system is based o n t h e decimal system of numhers- n o t t h e best choice. ~ e r h a n s h. u t too firmlv established t o question a t this la;e'date.-The fundamen& S I unit of time is t h e second, with which we can have n o quarrel. However, because of t h e solar system, time is lived in days a n d vears, a n d such untidv bits and collections thereof as minutes, hours, weeks a n d months. T h e more abstract common timd units t h a t we d o n o t experience, such a s centuries a n d milleniums, are decimal expressions. Other areas of science either haven't heard of t h e SI system or are ignoring it. Astronomers show n o tendency t o discard their delightfully mixed lightyears, a n d geologists with their mind-boggling time spans aren't a b o u t t o compound their problems by dropping years i n favor of seconds. Chemists who live i n real time seem t o favor minutes, hours, or days on t h e abscissa rather t h a n seconds b u t should have n o hang-ups about reporting such formal business as rate constants i n seconds.
I International System of Units (Fr., Le SysSme International d'Uniths), a metric system of units based on the meter, kilogram and second instead of the centimeter, gram and second. The changes involved, if the SI units were strictly observed, would be pervasive. For example (if the pH concept survived) the value of the term corresponding to pH in the SI system would be 4 for pure weter-the negative logarithm of lo-' "moles" of hydronium ion per cubic meter, or stere. McClashan, M.L., "Internationally Recommended Names and Symbols for Physicochemical Quantities and Units," in Annuol Remew of Physical Chemistry," Vol. 24, (Editors: Eyring, H., Christensen, C. J.. and Johnston, H. S.) Annual Review Inc., Palo Alto. 1973, p. 52. W a r i s , W. G., Mwre, J. W., and Collins, R. W., J. CHEM. EDUC.,
53.681 (197fi).
r damson: A. W., "Physical Chemistry of Surfaces," 3rd. ed., John Wiley & Sons, New York, 1976, p. viii. "Lainen, H. A., Anal. Chem., 48,633 (1976). 638 1 Journal of Chemical Education
Resistance to the new energy units is probably a battle already laat. Quiet surrender to let the theorists properly enshrine their patron saints would he the better part of valor to save strength to fight the war against enforced conformity of expre~sionfor volume and mass units. I oersonallv wish thev had named the kilocalorie after someone. An erg is something I don't grasp readily-much less ten million of them in a joule. A calorie I understand and 1 can mentally line up a thousand of them without too much strain. The SI system proposes we go straight from ergs to joules without touching base with kilocalurie*. S ~ m eimportant demotims and ddetiuns haw heen proposed under the SI system. 'l'hr charge on Avogsdm's numherof e.retmns t9fi4845ti X IO'cuulombst would no lonerr be a farndsv. ..but Varndav iives on in truncated fork as the farad jthe unit of electrical caoaei-
sloppy term "mole" would supplant the more descriptive and precise gram-atom, gram-molecule, gram-ion, grem-equivalent, and gramformula. Chemistry teachers who have carefully pointed out to students that "mole" is acontract of pram-molecular weight and hence should be applied cautiously to sudstances composed ofions now find themselves in danger of being stranded on their own semantics. The real hackle-raiser is the proposition that concentrations he expressed in a certain uniform manner. Theoretical types, whose principal contact with reality is the point at which the graphite meets the cellulose, profess to see no problem in dealing with cubic meters of solutions. Some editors, whose horizon is the publication date of the next issue, will cheerfully applaud any uniformity that will get the show on the road. One editor-Herb Laitinen of Analytical Chemistrys-is enough of a realist to predict that handy volumes such as the milliliter and the microliter will he with us for at least the next gigasecond. That calculates out to be 31.7 365-dayyears, which should he enough time for hoth of us to exit gracefully if SI units should D ~ ,~ ..P V I ~ ~ ~
I t is preriialy the psychdogid advantage of dealing w ~ r heasily romprehcndrd sizesand numhers that wwld he larkin: i n thestrict appli
