Irwin Cohen and Robert Fewerolf' Youngstown University
Youngstown, Ohio
Programed Instruction in Qualitative Analysis Laboratory
Two of the three basic ideas of programing, careful and patient development of the subject and personal involvement by the student, are already included in the usual course in qualitative inorganic analysis to the limited extent that there is an orderly sequence of the analytical groups and personal involvement in the laboratory unknowns. However, the sequence of groups is not an orderly introduct,ion to the principles of analysis, and the personal involvement is directed toward solving the unknowns rather t,han toward understanding the method of analysis. With these difficulties as t,he point of departure, the qualitative inorganic course has been found to he well suited for a t,rial of programing in the laboratory. We would like to start the student with the idea of doing one thing at a time. However, even the simplest analytical groups involve not one but several distinct principles. For example, the cation group silver, mercury(I), and lead involves the group precipitation, the variation of solubility with temperature, complex ammine formation and its reversal through acid-hase neutralization, and a redox disproportionation with the appearance of a basic amide. From the viewpoint of programing, this is much too much. It is even, perhaps, disorderly, or a t least so appears to the st,udent. Therefore, adherence to sound programing principles means that we should abandon the analytical groups as the units of instruction.2 Just as we do not t,each organic or inorganic chemistry by following the flow sheets of industrial production, so also we should not t,each qualitative analysis by following an analytical sequence. What we ought to do is to develop an analytical sequence by way of a pedagogical sequence, based on principles rather than on groups. We ought to teach the principles of analysis rather than a particular scheme of analysis, so that a student then can follow intelligently any given scheme and, when the occasion arises, devise his own. A first principle in qualitative analysis is solubility. The starting point in this principles approach should therefore he a group of substances that can he differentiated by solubility considerations alone. One possible starting point is the four substances composed
of the sodium, calcium, chloride, and carbonate ions. (Calcium carbonate is insoluble, and of the three soluble substances, calcium chloride forms a precipitate when its solution is mixed with one of sodium carbonate, a solution of sodium carbonate forms a precipitate when mixed with calcium chloride, and sodium chloride forms no precipitate with the others.) An unknown from this list would he too easy a problem. This points our attention to the second difficulty in the course and introduces the second change in constructing the program. The laboratory part of the traditional course is concerned with the work of the technician rather than with that of the c h e m i ~ t . ~So, before asking a student to identify an unknown, we ask him to Jim? out how to identify it.' The laboratory work thus changes from the technician's approach, learning a scheme of analysis, to the chemist's approach, learning how to devise a scheme of analysis. I t is not enough only to ask the student to devise his own scheme; he should also participate, through programing, in the study of t,he techniques, reasoning, and principles by which a scheme is set up. I t is the combination of this chemist's approach with the principles approach that results in a programed course. The program we have developed (chiefly in the second semester freshman laboratory in the course for liberal arts students) a t present consists of nine steps. First, given four substances as known solids, the student experiments with them to find out how they can he differentiated, and then identifies an unknown by his own procedure. On finishing this, the student's answer-his unknown report-is checked. If he is right he can confidently proceed further in the same manner; if there is an error, it is discussed with the instructor before going on. In practice, mistakes are rare. The next steps are, (2) solutions of the four substances; (3) nine substances-three cations, three anions; (4) more than one solute in an unknown; (5) five cations, five anions; (6) the given ions in the presence of new, unknown ions; (7) development of the chloride and sulfide cation groups; (5) ten cations, five anions; and (9) addition of new, unfamiliar ions to an unknown which also contains some ions which the student has already studied. For example, in the second major step, the student devises his own scheme for differentiating solutions of four ions (studied in the first step) from each other and
Presented at the Symposium on Pragrrtmed Instruction at the 124th meeting of the American Chemical Society, Atlantic City, New Jersey, September, 1962. I Present address: The University of Florida, Gainesville. a Suggestions for alternatives to an analytical scheme as the basis of instruction have been made, for example, by R. BATTINO, Abstracts of Papers, American Chemical Society Meeting, SepA. A,, SCHNEIDER, F., a See, for example, in Tnrs JOURNAL, SUMKERBELL, R. K., tember, 1960, p. 15f; BENEDETTI-PICHLER, AND STEINBACH, 0. F., THIS JOURNAL, 34, 381 (1957); FRANK, 31, 365 (1954); and SUMMERBELL, R. K., LESTINA,G., KING, H.M.,THIS JOURNAL, 32,475 (1955). h L R.,THIS JOURNAL, 34,383 (1957); STRONG, F. C., THIS J O U R N A ~ L. C., AND NEUMAN, "n important step in this directionwas taken by BATTINO, 34, 401 (1957); VASILAKES, W., THIS JOURNAL, 38, 146 (1961); a p . cit. and FOWLES, G . W. A,, THIS JOURNAL 39,401 (1962).
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from water. As the number of ions to be distinguished is increased in the remaining several major steps, other complexities are carefully introduced, and the student is taught, one by one, how to deal with each of these. (This, obviously, requires careful selection of the new "unknown" ions selected as the added ions, as the procedure becomes more complex.) Examples of new concepts which are learned, one at a time, are: the importance of the order of addition of test reagents, the reliability of the evidence which indicates the presumed presence, or absence of an ion; interfering ions; the convenience of separate testing for anions and for cations; the concept of a weak acid; ionization equilibria; pH; confirmatory testing; Sr@nstedacids and bases.8 Special techniques such as paper chromatography, flame spectroscopy, handling of solids; and other similar concepts may also be introduced. The third basic idea of programing is immediate reinforcement, by the inclusion of answers within the program. In a laboratory program, however, answers are immediately given, not by the written work but by the test tube, although hints do need to be given to avoid misinterpretation or to improve technique. I n programing qualitative analysis, the unknowns are a major factor; they are easy to grade quickly and any errors can he checked over and discussed with the st,udent. I n the verbal parts of this program, answers are not written in (as they are in a linear program) but rather the student checks his work continually with the instructor. This is possible and probably advisable here because the program is intended only for class work in the laboratory rather than-as most programing is-as a private tutorial aid. Furthermore, it is desired here to emphasize the laboratory work as an experimental rather than a verbal study. For the same reason, the theoretical background, which is of course necessary in the full course, is not included in t,he laboratory program. All verbal parts are held as much as possible t,o a distinctly supplementary role. It may he questioned whether this application of programing should indeed be called programing, since the answers to the questions are thus not supplied in the written program itself for immediate checking. To us, the form of the answers, visual or oral or written, does not constitute an essential difference. Of course, confirmation of the student's answer, which is given 6 Detailed descriptions of the analytical procedures involved in the nine steps can beobtained on request from Cohen. Briefly, each of the nine steps is composed of a series of smaller steps, in which the student is directed to carry out laboratory studies not unlike, in its use of explicit directions, those found in some laboratory manuals for elementary chemistry. The ditference lies in what is done by the student as a result of his observations when the directions are followed.
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by the instructor, is not generally as immediate as the answer given in the usual form of programing. The question is, how immediate must the answer be confirmed for effective reinforcement? The answer to this must be supplied by psychology, but it is suggested here that as long as a program is written so as to elicit close to 100% correct answers, the verification may perhaps wait for several minutes or Ionper without serious harm. The verbal parts of a laboratory program such as this could in fact be written in the usual manner. althounh it would not then be so easy to integrate them with the laboratory parts. A laboratory program in itself always has its own immediate reinforcement through events occurring in the test tube. The difference between a programed laboratory instruct,ion and the typical laboratory class lies principally in the conversion of a collection of individualized hut impersonal demonstrations int.0 a careful and patient development of principles in which the student is a participant instead of an observer. This experiment in programing has been developed over a three-year period. The maximum use so far has been 24 laboratory hours. No attempt has been made to measure the results by a statistical analysis, nor is it suggested that the program is already perfected or is a finished course in qualitative analysis. But we feel that it is a sound introduction. Throughout the program, it is inevitable that some students make false starts and waste time on blind alleys. But they enjoy it. They are discovering things. They can see their progress as an analytical scheme emerges and as they find that they are able to master the continually expanding list of ions. I n contrast to t,he usual course in which there is a slow start with many unknowns coming later, here the students solve two unknowns in the first two hours of work and then proceed more slowly as they see and seek to understand the growing complications. The steps throughout are small enough for them to find their own way, and they arepersonally involved in what they are doing. The freshman students, the instructor, and the senior student who scouted the way all enjoyed the work, learned much about analytical chemistry, and exercised greater initiative and imagination than would otherwise have been the case. Laboratory programing is feasible and rewarding both for the class and t,he instructor. I t is hoped that those who have not yet tried it will do so.
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Acknowledgment
The authorir are indebted to Prof. Young for several important suggestions on the presentation of this paper.
