TOBIAS H. DUNKELBERGER Duquesne University, Pittsburgh, Pennsylvania
THERE is some tendency for styles in chemical educa- narily presented are really not sufficient if we're iutertion to change with time much as do styles in anything ested merely in detecting the components of an arbitrary else. No one today questions the fundamental impor- mixture. Organic compounds are omitted; the selectance of quantitative analysis in the education of a tion of cations is not adequate to analyze even a simple chemist, but i t is not without significance to note that alloy steel; anions are commonly treated hastily or during the nineteenth century qualitative analysis oc- even omitted altogether; silicates, especially, though cupied a similarly important position in the university they comprise the great mass of the earth's crust, are chemistry program. In his interesting and amusing commonly considered too troublesome to include. paper on his student days in Germany, McKay2 tells Moreover, spectrographs and other instruments, with a how much attention was given to qualitative analysis in speed that no chemical analyst can match, will answer Bunsen's laboratory and in other German laboratories. many of our questions about the constitution of a samEven in this twentieth century many of us put in a full ple. As a result of this essential impracticality, courses year or more of work in a course in qualitative analysis. in qualitative analysis have become, to a very great exBut during the past twenty years the qualitative tent, vehicles on which are loaded a burden of thenreticourse has declined steadily and extensively in promi- cal and descriptive material much of which does not fit nence and prestige until now it is sometimes omitted al- easily into any other course. This situation developed in an entirely normal way. together or, in many schools, included as part of the work in general chemistry laboratory, with little or no Chemistry began as a descriptive science and to a considerable extent still remains one. Early chemists classroom discussion. Does this decline represent merely a yielding to the were greatly preoccupied with preparation, separation, pressure for including more and more new kinds of ma- and characterization of materials. Since this type of terial in our chemistry course? Did the former promi- activity is closely allied to that in qualitative analysis it nence reflect only the paucity of information in the is not difficult to understand the emphasis that was long other branches of chemistry? Have modern chemical placed on the latter. During the years when new eleeducators become cynical about the value of the work ments were being discovered periodically there was a in qualitative? Were the values that justified its in- sort of glamor attached to the work which, I fear, our clusion a generation ago merely imaginary ones or, if students now largely fail to see or appreciate. With real, are they now being realized in other parts of the the development of physical chemistry, particularly, the program? Are those of us who still teach it-and a t emphasis gradnally changed from the descriptive to the times even defend it-merely old fogies supporting a interpretative aspects of the science. Some chemists, lost cause because of vested interests or because we notably Stieglitz, attempted to fuse the t w e t h a t is, to simply cannot see the direction in which chemistry is de- superpose on the empirically developed methods of analysis a physicochemical interpretation. This attempt veloping? These are some of the questions that demand answers was so successful that nowadays any self-respecting when we are trying to decide the place, if any, of quali- course in analytical chemistry includes large portions of tative analysis in the chemistry program. Others on equilibrium theory. In fact, this is now presented as numerous occasions have raised the very points that I one of the better reasons for offering courses in qualitashall consider; nevertheless, I want to present some as- tive analysis. To summarize, then, a generation ago the work in pects of my own evaluation. qualitative analysis apparently was intended to accomDECLINE OF QUALITATIVE ANALYSIS wlish the followina ends: One important factor in the decline in importance of 1, present,didactically and experimentally, incourses in qualitative analysis has no doubt been the formation the appearance and properties of a realization that qualitative analysis as ord'marily number of inorganic compounds, 2. T~ develop, didactically and experimentaught can hardly justify itself as a practical art. Anyone will agree that the schemes of analysis as ordi- tally, knowledge about, and experience in, utilizing differences in properties to effectseparations. Presented as part of the S~mposiumon Teaching Qualitative 3, T~ explain and illustrate the application of genAnalysis a t the 117th Meeting of the American Chemical Society, era1 chemical principles, especially equilibrium considPhiladelphia, April, 1950. erations, to numerous specific reactions and situations. MCKAY,L. W., J. CHEM. EDUC., 7,1081 (1930).
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4. To develop, experimentally, facility in deductive reasoning, skill in recognizing, evaluating, and correcting the situation that is "not according to Hoyle," and ingenuity in devising procedures for particular purposes.
ACHIEVEMENT OF OBJECTIVES All of this raises the questions of whether such material is really indispensable, whether it might better be included elsewhere, whether the outlined values are in fact realized in the course, and whether the values allegedly derived from qualitative work justify all the bother. First of all, are these still reasonable aims in teaching chemistry? Most would agree that they are worth while, though not, of course, the only aims that should be considered. Will they be adequately covered in other courses if qualitative is abandoned? Most would agree that this is not completely assured. Are there more pressing demands for other types of material-demands that could be met if the qualitative course were sacrificed? The answer to this question requires a complete overview of the entire chemistry curriculum and, in general, the answers will have a highly individualistic flavor determined by the particular interest of the persons giving them. Everyone, of course, wants the program to include more of everything, including, particularly, his own specialty. It is, 'as I see it, valuable to debate this point hut hopeless to expect to arrive a t an unequivocal answer. That many chemical educators think these other demands are more pressing is, however, indicated by the move toward deemphasizing the qualitative course. Are the alleged aims in fact accomplished in courses in qualitative analysis? This is the crucial question and most would hesitate to give an unqualified affirmative answer. It is, again, because so many chemists answer this question negatively that qualitative analysis has declined so greatly in prestige. But if the values mentioned are worth striving for a t all, the way in which the qualitative course is being so extensively modified seems to me to he in the wrong direction, with the result that, in my experience, frequently very little value is derived from the work. One fundamental difficulty with qualitative courses seems to be that the work tends to degenerate into the much deplored cookbook chemistry, with students going blindly through lengthy procedures to end up with results of questionable significance. Such blindness can be remedied only by giving the student appropriate preliminary information before he undertakes the laboratory work. Qualitative analysis is, unfortunately, one of those courses in which the student should know a t the beginning everything that he knows a t the end if he is to carry out the laboratory work reasonably intelligently. Pity the poor teacher! At the very beginniig of the course he sees urgent need for instruction in writing and balancing equations, in formulating complex ions, in cal-
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culating concentrations of solutions, soluhility-product and ionization equilibria, pH, and so on and so on. Something is bound to be left until later in the semester and it isn't necessarily the least important material. Then, near the end of the semester, when he does get around to some of these topics, as likely as not the students will ask, "Why didn't you tell us about that in the first place?" QUALITATIVE VS. QUANTITATIVE ANALYSIS Consider, on the other hand, the corresponding situation with respect to quantitative analysis. If we start with gravimetric work (which seems to me to be the least complicated both theoretically and experimentally) the background of information needed to perform intelligently in the laboratory is much less; all you really need is knowledge of the law of definite proportions and information on how to use the balance. Such information is included in every general chemistry lahoratory course. During the weeks in which reasonably intelligent work is being done on gravimetric determinations thelecturerhasanopportunity topresent stoichiometry and the stoichiometric basis of volumetric analysis, including, all along, practice in writing and balancing equations. While the laboratory work in volumetric analysis is proceeding, again reasonably intelligently, the lecturer can cultivate equilibrium theory and similar topics. At every stage, then, the necessary theoretical material can be presented either before or in connection with the corresponding laboratory utilization of it. But this supplies in large part the information urgently needed before beginning the work in qualitative analysis. Consequently itappears that the factors limiting the realization of the potentialvalues of the course in qualitative analysis can be largely eliminated by simply interchanging the traditional order of these two courses. Before we can do this we must, however, rid ourselves of two common fallacies in our thinking about these two courses. The first fallacy is that our work in analytical chemistry must follow the logical sequence of discovering what is present before we determine how much. Actually, who now requires a qualitative analysis of a sample submitted for quantitative analysis? So far as I know, everyone tells the student the general nature of his quantitative samples; we also ordinarily tell him the nature of the interferences or assure him that none are present. The second fallacy is that experimental qualitative analvsis is easier than auantitative analvsis. On the contrary, I tell my studknts, qualitative"analysis with no holes barred is the toughest branch of chemistry. Even teachers are likely to forget the extent to which laboratory courses in qualitative analysis are artificially simplified bg omitting trouble-making components: we leave out organic compounds, the rare earths, tungsten, molybdenum, vanadium, commonly silicates and fluorides, oxalates and tartrates. In fact we end up with a severely restricted collection of ions, some of
JOURNAL OF CHEMICAL EDUCATION
which justify their inclusion not by their relative importance but by their essentially trouble-free characteristics. Compared with the difficulty of accomplishing the separation from the extraneous materials, the h a 1 quantitative estimation is usually quite simple. In the eyes of students qualitative analysis seems t o be easier than quantitative partially because it does not ordinarily demand the extreme care and resulting tenseness; it is this tenseness that they mind. INVERTING THE ORDER
This inverted arrangement of the two courses has been in operation a t Duquesne University for five years and it is now possible to attempt an evaluation of some parts of it. The analytical work falls normally in the sophomore year and consists of three lecture-recitation periods and eight hours of laboratory work each week for two sixteen-week semesters. The textbook in quautitative has been Kolthoff and Sande113 and in qualitative, Curtman.' As preparation for this work a considerable portion of the second semester's work in general chemistry is devoted to quantitative experiments: gravimetric chloride, volumetric soda ash, and oxalate by permangauate, for example. As a result, studeuts entering the analytical course have a fair acquaintance with stoichiometry and with the techniques of weighing, -. filtering, and titrating. It is difficult to establish the success or failure of the plan as a whole as there are no obvious criteria that can be applied and no simple way to set up and evaluate control groups. After fairly extensive experience with both arrangements I have come to the conclusion that this is more satisfactory than the traditional one. One incidental value seems t o be an improvement in the laboratory work in qualitative. Apparently some of the careful attention to detail learned in the quantitative work carries over into the subsequent course. So far as I can tell the quantitative work is as good in quality as under the usual system but it seems that at first the students work more slowly; hence there is greater difficulty in having them complete a satisfactory number of determinations. We try t o maintain a schedule of one determination per week but we are usually satisfied if they complete twelve during the semester. The unavailability of appropriate texts is a difficulty and a handicap. Most quantitative texts assume a knowledge of qualitative; most qualitative texts assume KOLTAOFF, I. M., AND E. B. SLNDELL, "Textbopk of Quantitative Inorganic Analysis," The Macrnillm Co.,New York, 1943. ' CURTUN, L. J., "Quditative Chemical Analysis," The Maomillan Co., New York, 1938.
only fragmentary knowledge of, for example, stoichiometry and equation writing. Consequently, the lecturer has to shoulder a considerable burden of presenting material not in the text and rearranging the material that is there. Along with such a rearrangement of material there is almost necesssarily a somewhat different selection. The quantitative course, for example, is somewhat deficient in discussion of procedures not actually carried out in the laboratory. The qualitative course, on the other hand, is considerably enriched. It includes, for example, a fairly extensive discussion of general acidbase theory and of the stmctuwl factors that determine acid strength, a consideration of the formation and properties of precipitates, and an outline of the chemistry of some of the elements not included in the schemes of analysis. Eventually we hope t o modify the traditional laboratory work in qualitative rather extensively. There seems to be little point in going through the usual schemes of analysis more than once or twice a t the expense of new and different kinds of procedures. At present we do preliminary experiments, a known mixture, and an unknown for each cation group. This is followed by a general cation unknown, and then the anions are treated similarly. Silicates, fluorides, oxalates, tartrates, and all the usual anions are included in the anion work. Finally there is a complex mixture t o be examined for both cations and anions. This mixture is always made up in such a way as to require a carbonate. transposition. If a student finishes early, as is sometimes the case, he is simply given more work of the same kind. It is our hope to introduce, instead of such repetition, some experiments of a physical nature, such as the use of a pH meter for adjusting the acidity before precipitating cation Group 11, an experimental determination of an equilibrium constant, or perhaps some preliminary work with important but neglected metals such as vanadium, molybdenum, and titanium. Those who hold the responsibility of "tooling-up" laboratories for new procedures and instmeting assistants to take charge of experiments they probably have never performed themselves will understand why modifications of this sort have not already been carried out. In conclus?on, I want t.o enter a strong plea for a continuing critical attitude toward all aspects of our traditional chemistry program, backed up, where possible and feasible, by an appropriate experimental approach. By such an attitude, and only by such an attitude, can we be sure that our instruction will keep pace with the rapidly changing emphases in the great world of chemistry and only in this way can we prepare our students adequately to assume without too serious handicap the burdens that will be thrown a t them when they leave school to become a part of that world.
