Measurement or Interpretation?
provocative opinion
In the past year or two, three graduate students from three different departments have approached me for help. One was studying turbulent flow mixing with a conductivity probe which was being terribly insensitive. (It consisted of an epoxy-insulated wire in the lumen of a hypodermic needle, the two electrodes being the end of the wire and the annular tip of the needle, and its equivalent circuit would be best rcpresentcd as a slightly-leaky capacitor). Another wanted to be loaned a glass electrode so he could see if the one he already had was the source of his "wrong" answer. (Asked if his buffers were freshly-made, he queried, "What would I need buffers for?") The third wanted to borrow a pH meter to study the effect of a 20 kV electric field on the pH of a model blood serum he had prepared. (The model serum had a pH greater than nine.) Now, all these students had respectable first dcgrces. All had discussed their problems wit,h their own supervisors (or had they?) before seeking other help. All were prepared to tell me why they were doing their experiments, and what the results would mean. There was only one small hitchget.ting measurements to support the waiting interpretation. I remcmbcr these incidents when I listen to undergraduates in t,he lab: "After all, labs are just to illustrate bits of theory from the lectures." I remember them when colleagues remark over coffee, "After all, the student ncedn't run the (nmr, XRD, DTA, FIR, RfS, you name it,) as long as he is given charts to interpret. Hc can watch the technician, or we could makc a videotape and students wouldn't have to clutter up the machine room." I remember them as I listen to the budget-watchers: "We can't afford to run as many hours of labs.. .." "We need to make more efficient use of every lab hour, so we can't afford to have experiments repeated." I remcmber t,hem also as I think of students required to rework Ph.D. theses for t,he inadequacy of experimental verification of mathematical modeling exercises. Just how were they expected to finally decide that measurements were important? What arc we trying to do by this trend away from teaching how to make valid experimental measurements? Do we wish to produce more of the ignorant bliss displayed by the research students I mentioned? Do we intend to teach that facbs merely illustrate (and are sclccted to support) theories? Should t,he student learn that, the business of a chemist is explaining a curve on a piece of paper (which may bc revealing that a slidewire was dirty, or that a line voltage changed or that a sample was not quantitatively transferred or that it was now 3 P.M. and the sun was able to shine on the thermocouple)? 226
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Journal o f Chemical Educoiion
It is very easy to begin requiring students to perform experiments which exemplify or illustrate some point of theory, thus conveying the idea that the theory was derived and brought to its present state by similar measurements. Somewhere along the line, the student needs to learn that thc object of much chemical activity is getting quantitatively correct answers. This serves both thc mundane purposes of characterizing materials to keep t,he chemical process industries functioning, and the more esoteric purposes of providing both the need to improve, and the means of improving, chemical theories. If any theory fits a wide range of cases to within one or two percent, it is highly successful; but such a theory nil1 never be devised or refined on the basis of measurements with one or two percent uncertainty. Measurement has its art. The details of the art change with the tools available, but the art remains, and the studcnt chemist must learn it. He will not necessarily practice it himself in his later years, but unless he has experienced, e.g., making quantitative transfers of samples (as well as knowing the concept) how will he train the technician or assess the possible sources of uncertainty in a result? How will he decide whether the Beer-Lambert Law should be assumed to hold, or tested? Can hc prescribe and recognize laboratory techniques good enough to ensure that testing standards are prepared with an accuracy as good as, or preferably better than, today's increasingly accurate ph~tomet~ric devices? I suggest that our modern undergraduatc programs nccd a new subject to put alongside structure and bonding, chemical energetics, reaction mechanisms, and similar basically interpretive treatments of chemical phenomena. T h e new subject should be chemical measurement,, and its short definition might be "the methods of describing the properties and reactions of chemicals quantitatively." Chemical measurements xi11 thus draw upon thc contents of traditional laboratory courses in physical chemistry and in quantitative analysis. With a bit of luck, it may manage to eliminate the pragmatic versus theoretical dichotomy between these essentially measuring subjects, and may diminish both overlaps and gaps bctween their offerings. I t should nicely complement a synthetic chemistry laboratory course based on George Hammond's recently-suggested idea of the production of specified properties (Chem. Tech., January 1971, p. 24-26). I t is all too easy to suggest changcs in undergraduate lab programs, but often much too expensive to implement them. However, the setting up of a chemical measuremmts laboratory is likely to liberate as surplus
some of the presently-duplicated equipment between analytical and physical laboratories. A further bonus may be the production of students a t least as interested in "getting it right" as in "making it fit." In an age when the pesticide experts are asking the meaning of zero concentration, and the solid state scientists are measuring impurities as atoms per cm8, some measurement-minded people might be as useful as quantum mechanics. For the university concerned,
the attempt to produce them would he an interesting exercise in the production of specified properties. And without doubt such graduates would be highly employable into varied and interesting careers.
George F. Afkinson Universiy of Waterloo Waterloo, Ontario, Canada
Volume 49, Number 4, April 1972
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