Relevant Analytical Experiments-with
Accountability
Nothing learned poorly is long releuant: Nothing learned well is predictably irreleuont, in the /on8 run.' In a recent article, CorwinZ stresses the advantages of using "real" samples in quantitative analytical laboratory exercises. We, too, have found that the use of "real" samples increases student interest in chemical analysis, and confronts realistically the problems of sampling, separation, and interferences in ways that prepared unknowns cannot. Nevertheless, exclusive use of real samples (the exact compositions of which are unknown even to the instructor) has the undesirable side effect of removing from the student his accountability for accurate determinations. The student is, in effect, rewarded for giving a good imitation of a chemist performing a quantitative experiment, rather than for actually learning to perform quantitatively. In response to this objection we have instituted a simple, practical, and instructive addition to the "relevant" experiment which preserves the tradition of accountability in a realistic fashion. Along with the "real" sample, each student is given a "check sample" to be analyzed. The "check sample" may, in ideal cases, he a n NBS-certified Standard Reference Material.= Other possibilities are commercially prepared "unknowns," locally prepared solutions, or (in cases in which separation and/or interference is crucial to analysis) a portion of the "real" sample to which a standard addition of the analyte has been made confidentially by the instructor.' This simole exoedient is not oarticularlv time-consuming, since titrant or other necessary preparations are already a t hand for use with the "real" sample. In addition t o its direct pedagogical benefit of stressing the value of analytical accuracy, this process is illustrative of a practice which is (or should he) standard procedure in any "real" analytical laboratory. 'Bent, H. A., Chemistry, 44.6 (1911). 2Corwin, James F., J. CHEM. EDUC., 48,523 (1971). 3SeeAnol. Chem., 38,27A (1966). 41n this case, the check-value is the difference between the real and the augmented sample values. Monmouth College Monmouth, Illinois 61462
822 /Journal of Chemical Education
Berwyn E. Jones
