QUALITATIVE ANALYSIS IN THE TRAINING OF CHEMISTS' A. A. BENEDETTI-PICHLER, FRANK SCHNEIDER, and OTTO F. STEINBACH Queens College, Flushing, New York
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may assume that the chemists of the nest generation should be experts in dealing with matter, i.e., its recognition, preparation, purification, and use. They should he better prepared in this respect than the graduate of the present day who shows often a quite noticeable lack of knowledge concerning the appearance as well as the physical and chemical properties of common substances. Evidence is all around us. Graduates of one school will spend five minutes going over a shelf displaying nothing but colorless substances when searching for potassium dichromate or copper acetate. Our own students are quite frequently surprised and puzzled by the separation of the mixed oxides during the analysis of limestone, and the mention of brass seems to call up visions of a band or an x-star general! It is quite certain that these shortcomings of bachelordegree graduates may not be remedied by graduate studies which by necessity will have to focus more and more upon advanced theory, nucleonics, and complex instrumentation. WEAKNESS OF GENERAL CHEMISTRY LABORATORY
The American college may take credit for the fact that it is obviously making up for the deficiencies of entering freshmen. Only this and the natural ability of individual students can explain the excellence of so many of America's professional men. The task of the college is certainly not a simple one, and one wrong decision made some 50 years ago in the chemistry curriculum cannot rate but a minor flaw. We mean the decision to support the lecture in general chemistry by a general chemistry laboratory. The general chemistry laboratory is bound to fail in the task of familiarizing the student with the appearance and properties of matter since it violates basic requirements of good teaching. Above all it fails to arouse the consuming interest that is essential if the memory is to retain facts. We are fully aware that better minds than ours have struggled with the problem of the general chemistry laboratory and its organization for mass instruction. We are also convinced that the general chemistry laboratory a t our own institution has been organized with special ingenuity and is operating under very favorable conditions. In spite of all this, it has been our observation that students are trvine " .. to away from the laboratory sessions as quickly as possible. This is an attitude which, as a rule, is not observed in other chemistry laboratories where Presented before the Division of Chemical Education a t the 130th Meeting of the Am~ricanChemical Society, Atlantic City, September, 1956.
the customary request is for additional hours of work. The failure to gain the interest of the students in the general chemistry laboratory is not surprising when one considers the type of experiments performed: repet,ition of harmless lecture experiments which some students may have seen already in high school and testtube experiments slyly selected to provide reasoning toward the key steps of separation for some halfhearted passes at qualitative analysis. There is no lack of suggestions for the improvement of the general chemistry laboratory. The teacher is exhorted to try his utmost to render thecourse interesting.2 We do not have enough teachers, however, who are able to overcome the boredom year after year by sheer genius and vitality. It seems more to the point to abandon an enterprise which proves very difficult and refuses to bring the desired results. The situation may be summarized by quoting from the preface of a book on "Laboratory Problems in General Chemi~try."~ Despite the impre3sive claims made for the importance of laboratory work in general rhemistry, it is disturbing to discover how much of i t consists in having the student mix several substances and then report a color, odor, or precipitate formation in
yet, who knows how m m y students prepare their lab reports the night before class from the textbook. . Laboratory work thus becomes not onlv moekerv of the word "exneriment" and a. de-
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periment and by the professor who grades it.
THE EXCITEMENT OF EXPERIMENT
Some general chemistry teachers have already recognized the superiority of qualitative analysis as a teaching instrument. At least, the article by Snmmerbell4 gives this impression: Almost every teacher of our now standard college freshman chemistry courses will testify t h a t the course comes to life when qualitative analysis is reached. This phenomenon . . . results from the fact that we are introducing the student, often for the first time, to the excitement of experiment. He has a real, if somewhat artificial problem, the contained ions of his unknown solution. [The italics are ours, the ~ c t u s l l y8uperfluous word indicates the undesirable general trend.] He proceeds to ask questions of nstnre by doing experiments, and nature answers. The teaching must be very infeeor or the student very stupid lo escape some of the ezcilemenl o j erperiment. [Itdics are again ours.] XAN,JOHN, J. CXEM.EDUC., 31, 519 (1954). a N ~ HOWARD, ~ "Laboratory ~ ~ Problems ~ ~ in General ~ ~ Chemistry,'' Thomas Y. Crowell Co., New York. 1954. ' SUMMERBELL, ROBERTK.. J. CHEM.EDUC.,31,365 (1954).
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One may add that even a simple unknown requirer the approach used in research: inspection of the problem and decision concerning the action to be taken, performance of experiments and observation, weighing of evidence, possibly decision on a final crucial experiment, and arriving at a conclusion. The student has a personal problem, and he is forced to do his own reasoning and to make decisions. There is also a keen interest in the outcome of the investigation whether the student feels that he is pitting his intelligence against nature or whether he is merely trying to outsmart his instructor. Furthermore the student will make an intentional effort toward the improvement of his technique a t least to such an extent that his experiments become able to give decisive answers to his questions. Above all, the student learns chemistry by repeatedly meeting the more common substances in different forms, in different combinations, and under different circumstances. His mind is captivated by the observation of phenomena and the attempt of correlating them with substances. Some elements will make a strong impression on his mind because of their clear-cut characteristics and the ease of their recognition, others will leave a mark on account of the trouble they give. Summerbel13points out, however, that
. . . as a tewhing device, qualitative analysis is far from ideal. The techniques are too repetitive to constitute good teaching practice. Not enough thought is required, since s. mediocre student, by slavishly following directions in oaokbook fashion, will emerge with satisfactory results. In spite of the unknowns, interest lags perceptively toward the end of the course. Summerbell then proceeds to make a remedial suggestion which would he worth while to consider in connection with an advanced course in qualitative analysis. Commenting, we like to point out that repetition is good teaching practice. The monotony of excessive repetition is prevented by offering alternatives of technique and a choice of schemes of separations. Summerbell's criticism is, however, entirely justified if qualitative analysis is taught as is customary today. EMPHASIS ON OBSERVATION AND INTERPRETATION
In the teaching of beginners' qualitative analysis, many have strayed from the proper course because of the tacit assumption that qualitative analysis is taught for its own sake. This and the overemphasis on grades and, consequently, on correctness of reported findings seem to have led to the use of carefully tested procedures and detailed directions. In addition to the very undesirable preoccupation with the analysis of solutions, the students are supplied with elaborate schemes stating quantities and concentrations of reagents and frequently numbering solutions and precipitates in order to avoid confusion. If flow sheets are provided in addition to the .detailed directions, most students do not take the time for studying them and do not have the slightest notions concerning the reactions and substances occurring in their solutions and precipitates. I t is far more efficient to refer to the thing as "Precipitate No. 17" than to say "the residue from the extraction of the hydrous oxides with alkali hydroxide and bromine, which is supposed to be hydrous ferric oxide."
Whereas carefully tested, elaborate schemes are required if qualitative analysis shall be practiced with some assurance of success, they completely defeat the real teaching goal of a beginners' course. For the teaching of chemistry, the information should not go beyond the statement of principle, which is best supplied in the form of simple flow sheets. The student then has no other means than observation and an understanding of the reactions involved for arriving a t sensible decisions as to what constitutes a proper amount or a proper excess of reagent. He is forced to read explanations concerning the requirements of the reaction (which should he stated in purely qualitative terms), and he is forced to make his decisions according to his observations on the reacting system and his interpretations of these observations. He will not produce anything but ridiculous conclusions unless he familiarizes himself with the substances concerned and succeeds in understanding at least the main points of the chemistry involved. Today, there naturally is the problem of preventing the use of elaborate schemes which did not exist some 50 years ago. Obviously the freshman qualitative laboratory is also not the place for using automatic separations in columns or involved sensitive and specific tests for the circumvention of separations. Complex organic reagents should be avoided since they will produce little beyond a clutter of inane information of the type, "Cadmium is a red speck with Cadion." We recommend that qualitative analysis for he,'wlnners be based upon some ancient books on qualitative analysis, which retained plenty of emphasis upon the simple field tests of the mineralogists. Most useful would be a book presenting mainly tables and flow sheets bare of any quantitative information. We recommend one or better two terms with three to six lahoratory hours and one hour of seminar per week. The seminar should be used for the demonstration of laboratory technique; interruption of laboratory work by lengthy demonstrations or explanations is an abomination. The seminar may serve to settle once and for all the meanings of "colorless," "clear," "turbid," "opalescence,"and "precipitate." The proper use of two kinds of illumination for the observation of color and heterogeneity should be discussed, and a simple nepheloscope should be made available in the lahoratory. The seminar would also be the place for a systematic discussion of melting point, volatility, hardness, color, streak, and solubility of the more common substances. This may be done with reference to the periodic table, the analytical classification, or both. It is not sufficiently realized that a solubility table provides the key to most of the analytical separations 'nd that it is very simpleto remember a solubility table in qualitative terms. The seminar should also be used for demonstrating the reactions of the more common elements, and this demonstration may he combined with a discussion of the various consequences of the law of chemical equilibrium. Emphasis should, however, remain upon the demonstrations which should teach proper technique and should be performed by the lecturer himself. This is the occasion for teaching how to open bottles, how to care for the purity of reagents, and how to use a Bunsen burner, blast lamp, blowpipe, etc. We JOURNAL OF CHEMICAL EDUCATION
do not think that any time can he spared for quizzes and examinations; the grade should be based upon the laboratory reports and the observation of the student in the laboratory. The laboratory work should consist of preliminary experiments with known substances and analyses of a large number of simple unknowns. Emphasis should be on the analysis of solids and the use of "dry" tests (flame test, bead test, heating in the tube, heating on charcoal, testing with dilute and with concentrated sulfuric acid). All required reagents should be continuously displayed on shelves; only the formulas should appear on the labels. Getting the reagents from a systematically arranged shelf is in itself a teaching device. As to the scale of experimentation, it seems best to offer a choice of macro and semimicro techniques. Doubts are occasionally raised concerning the suitability of qualitative analysis for mass training in the freshman year. We do not believe such doubts
VOLUME 34, NO. 8, AUGUST, 1957
justified since qualitative analysis requires only simple apparatus. On the mental side, qualitative analysis represents the historical approach since chemical science had to start with the investigation of the nature of matter. The instructor of the freshman year should find it more congenial with the atmosphere of a college to act as scientific adviser in a qualitative laboratory than to be the disciplinarian, generator of a somewhat synthetic enthusiasm, and rather arbitrary grading machine of a general chemistry laboratory section. A further course in qualitative analysis should follow the course described above. It would have the benefit of working with students having considerable knowledge of the more common substances. Discussions of theory will meet better understanding and the practice of refined laboratory technique will be appreciated. The advanced course could justifiably strive to include micro technique, chemical microscopy, extraction methods of separation, chromatographic techniques, and trace search with specific reagents.
