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DECEMBER, 1950
A PROPOSAL FOR A REVERSAL OF TRENDS! ERNEST H. SWIFT California Institute of Technology, Pasadena, California
INMY opinion there are certain
values which are potentially inherent in a course in qualitative analysis and which can he uniquely realized by a properly designed course, and they are as follows: First, such a course offers a unique opportunity for the classification, systematization, and correlation of a large and useful background of factual inorganic chemistry. This is true because the basis of qualitativc systems is a process of first making use of the more general properties of the elements for major group separa,tions, and thereafter proceeding to utilize increasingly more specificproperties in order to etyect the separations of subgroups, of ~ingleelements, and, finally, to make the confirmatory identification of single constituents. Unfortunately, the student frequently is swamped with detailed material before this general principle is adrquately emphasized. Second, the laboratory work of a course in qualitative analysis offers a unique opportunity for demonstrating the application of a wide variety of chemical principles to experimental work carried out by thv student himself. And a t this stage of his development there seems to be no substitute for such experimental work as a means for fixing these principles and their application; and it should be emphasized that these principles are applicable not only to qualitative analysis, hut to chemical processes of all kinds. Third, a course in qualitative analysis can he of fun?. tional value in illustrating and providing t.raining in I: wide variety of useful analytical techniques-and again emphasis should be placed on the fact that these techniques are not restricted to analyt,ical processes. As a collateral asset, and one which is frequently uniPresented ns pert oi tho Symposium on Teaching Qualitative Analysis a t the 117th Meeting of t,he American Chemical Society. Philadelphia, April, 1950.
derestimated, a courve in qualitative analysis offers rather unique opportunities for the development in the student of a quality which I shall call intuitive resourcafulness. Fortunately, no textbook of qualitative analysis can provide for all of the unforeseen possibilities which arise in the course of various analyses, especially under student use. Therefore a student is forced to face and solve situations on his own initiative; and although I may not be an ent,irely impartial observer, 1 believe that there is evidence that students who have had a good coarse in qualitative analysis develop this qua1it.y to a greater extent than otherwise. If we assume that these values exist and are capable of realization, we a.re required t,o find an explanation for the fact that the time allotted to courses in qualitative analysis is being rapidly decreased and in some institutions such courses have been completely abandoned. In seeking an explanation for this situation one is tempted to accept the situation as inevitable and to assign the blame to certain specific developments, such as the use of spectrographic methods, which have decreased the functional value of the conventional system of inorganic qualitative analysis. However, even with a full appreciation of these specific developments, these seems possible just,ification for a survey of the status of qualitative, and to a certain extent of analytical chemistry, from a much more general point of view. I shall hegin this survey by developing an analogy, and with full appreciation of the danger of argument by analogy. There seems to he considerable evidence for the validity of the observation, applicable to the development of hoth plant and animal organisms, that when growth stops, regression or degeneration begins. Cessation of growth may be caused by attainment of a hereditasy age limit or failure t,o adjust to changes in environment. This same generalization has been applied to social 01.ganisms, and is observed in Toynhee's treatment of the
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rise and decline of civilizations. 1 am inclined to believe that this principle can be a.pplied to science, and to particular fields of science. In science, and in any particular field of science, growth represents a trend from a more general, descriptive, and qualitative treatment. of the phenomena, principles, or techniques of that. field toward a treatment which is specialized and qutmtitat,ive. Furthermore, I am inclined to believe tbat. one measnre, and a reliable one, of the rate of growth in such a field of nrience is the research prodoct,ivit,y within that field. If, for the sake of argument, the above general principle and analogy are accepted, and if research activity is a valid meawre of the growth in a scientific field, me are forced to the conclusion that, qualitative analysis is in a questionable state of health. To pursue the aualogy further, the question then arises as to whether qu11it.ative analysis has reached its natural span (a.nd is approaching a senile old age) or whether it is in a process of adjustment to a changing environment. There is no doubt that the development of instmmental techuiqurs has represented a change in environment whereby the the conventional system of inorganic qualitative analysis has lost much of its functional value. In order t,o ascertain if qualitative analysis has reacted to meet t,his environmental change, one must look for signs of trends in that field. Certainly the most obvious such trend. and perhaps the only one in the past twenty years, has been the extensive shift from the macro to the semimicro scale of operation. I have the highest respect for the semimicro, micro, and ultra-micro techniques-+here they have been applied in. order to achieve a n increase in sensitivity or in accuracy of measurement to necessarily limited samples. But I believe you will agree that the application of the semi-micro technique to qualitative analysis has not resulted in a more exact, a more quantitative, or a more critical approach to qualitative analysis. Therefore, this development does not represent a normal scientific or functional growth, hut is rather an adaptation to environmental change whereby the conventional system of qualitative analysis has become essentially a pedagogical device for teaching inorganic chemistry to freshmen. I do not believe i t possible for a freshman course alone to realize the full potentialities of the subject, but, in a large majority of the institutions where qualitative analysis is given in the freshman course, there is no subsequent course of a more advanced nature. A freshman has not had the time previously, nor is he given the time during the course, to accumulate and assimilate the background of factual information which is necessary before he can appreciate the systemization and coordination which a qualitative system can make possible. He has not had time to acquire sufficient mastery of the many principles which are utilized in a qualitative system so that he can fully appreciate their application to his work. Nor has he had the t i e to acquire adequate experimental proficiency for him to fully exploit the experimental potentialities of the con-
JOURNAL OF CHEMICAL EDUCATION
ventional system of qualitative analysis, to gain confidence in his own experimental ability, or to gain respect for chemistry as an experimental science. Because of this I am afraid that too often we will find chemists who, when asked regarding their impression of their qualitat,ive course, will reply as one did: "One damn sloppy mess after another." Perhaps the first question me shonld have considered in a general survey of t,he status of qualit.ative analysis was our definition of the t,erm. [Jpon resort to the dict,ionary one finds the following: qualitative analysis-a (.hemica1 system for establishing the identity of the conqtituent or constituents composing a material. And in apposition one finds quantitative analysis defined as a vhemical system for c!stabIishing the quantity of these constituents. Even though there was little chance for confusion I initially restricted our considerations to systems of 'norganic qualitative analysis, since organic chemists are more nearly correct from a semantic point of view than are the inorganic chemists. The organic chemist is much more frequently interested in determining the identity of a single compound and is not interested in incidental minor impurities. On the other hand the inorganic qualitative system is designed and nsed not only for the detection of an arbitrary and extensive group of cations and anions, hut for obtaining additional information as to the quantity which may be present. Even the terms present and absent carry quantitative significance, since absent means not present in quantities above the arbitrary sensitivity limits of the particular system being used. Because of these facts, a system of inorganic qualitative analysis which is to be of functional value is of necessity quite extensive and complicated. As a result, in my opinion, a really effective qualitative analysis demands a much greater background of factual material, a more comprehensive grasp of principles, and the application of a wider variety of techniques than does the conventional idealized quantitative determination found in elementary texts. Now let us turn for a moment to the course in quantitative analysis. One of the criticisms which has been directed toward most such courses, and one which I helieve is quite justified, is that the work is tending to consist largely of highly idealized procedures, involving samples carefully selected to minimize interfering suhstances. As a result the student gets little opportunity to develop the resourcefulness required to cope with the situations which almost invariably arise in the analysis of "things as they are." As evidence of this might be cited occasions when I have seen graduate chemists who were dejected and resentful pictures of frustration after their first experience with such analyses. Stated differently, they had had no experience in quantitative separations. And is there any fundamental difference between quantitative and qualitative separations? Thus, to summarize the results of our general survey, we have seen first, that the trend in inorganic qualitative analysis is toward a less exact, less criticial, less quantitative treatment of the subject and that this trend is the result of a decline in the functional use
DECEMBER, 1950
of the field and of the attempt to adapt it as a pedagogical tool for teaching inorganic chemistry a t the freshman level. Secondly, we have seen that there is a certain amount of common territory between the fields of qualitative and quantitative analysis, specifically, the field of separations, and that there is common neglect of this field. Furthermore, this neglect is increasing because of the above mentioned trend in qualitative courses, and because of an increasing trend in elementary quantitative courses toward specialized instrumentation. I fully appreciate the rapidly increasing importance of instrumentation and the necessity for training in instrumental measurements, but the premature introduction of instrumentation into elementary courses, before mastery of the physical and physicochemical principles involved, mill tend to produce technicians rather than creative chemists. As a. result of the above survey I should like to submit, certain proposals for the consideration of those interested in t,he teaching of inorganic and a,nalytical chew istry. These proposals are submitted in generalized form and only as topics for consideration and evaluation, for there are many specific and local factors which cannot be considered in the time available. The experimental basis for these proposals is twenty or more years of trials and errors with ihe general trend having been and continuing to he in the directions proposed. First, I would like to propose, where the qualitative analysis course is given in the sophomore year, that there be a reversal of sequence and that the introductory quantitative analysis course he given first. I have indicated above my belief as to the relative requirements of principles, facts, and techniques of a qualitative analysis and a quantitative determination. Where it is desired to give work in qualitative analysis in the freshman year, I would propose that there be much less detailed material presented and much more emphasis placed upon correlation with the periodic table and the use of certain fundamental properties of the elements as means of effecting analytical objectives. Second, and returning to semantic considerations, 1 would propose that the name Qualitative Analysis he abandoned for the course to be given following the quantitative work. I would not be concerned as to the exact title; it could he Systematic Analytical Chemist,ry or any one of several similar tit,les. This may he unnecessary quibbling, but I believe, because of the present trend in qualitative analysis, that there is an advantage in avoiding that title, especially where qualitative work is retained in the freshman course. Third, I would propose that. the classwork of this course consist of a survey and a crit,icalevaluation of the general methods which are used for quantitative separations (the same methods used for group separations in systems of qualitative analysis). Here strong emphasis is placed upon conducting this survey from a systematic, a quantitative, and a cvitical basis. One fault with conventional systems of qualitative analysis arises from the fact that they have been so idealized for pedagogical convenience that students are led to believe that
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many separations are of practical value which are so imperfect that they should not have been used even as pedagogical devices. This survey would not restrict itself to precipitation methods, but would include separations based upon volat,ilization methods, upon solvent extraction, upon the use of the more general organic reagents, and even a consideration of the potentialities of ion exchange processes. Mass action principles having been developed in connection with the introductory quantitative course, they could he applied here much more quantitatively, hut much more critically, that is with a fuller realization of the limitations and liabilities involved. And, finally, I would propose that the laboratory work of this course consist of the analysis of "things as they are." Samples would be used which would force the student to begin with the preparation of the solntion, to study critically each step involved in the separation or elimination of interfering constituents, as well as the losses which occur in each of these steps, and to consider the most appropriate method for the quantitative determination of that constituent, regardless of whether it is of minor or major quantity. I am not proposing a return to the marathon or "complete" quantitative analysis, but rather the determination of a particular constituent in each sample. In such a course the student would not complete a large number of analyses in the time usually allotted, nor would he be able to attain the accuracy which is usually expected when idealized samples and rigidly prescribed procedures are used. But he would have a better conception of the background involved in such procedures and a more realistic appreciation of the difficulties involved in maintaining accuracy where a sequence of separations is involved. In other words, the introductory quantitative course would demonstrate the potential accuracy of quantitative gravimetric and volumetric measurement; this. course would demonstrate the liabilities and difficulties involved under practical conditions before these measurements can be applied. In conclusion, I am proposing a reversal of trends in the presentation of the material usually given in the socalled qualitative analysis course. A reversal from the present trend toward a more general and less exact presentation of facts, principles, and techniques; a reversal to a more quantitative and critical presentation of essentially the same material in both class and laboratory. This proposal is made in the belief that instead of such a course being considered as merely a pedagogical device it would become one of functional and professional value; and, furthermore, that the content of the course, call it what you will, would become worthy of research and development, that is, of scientific growth. I am sure the workers in quantitative analysis will be the first to emphasize the opportunities for research and development in the field of quantitative separations. Finally, I believe that such a reversal would result in this course becoming a much more effective pedagogical tool for the attainment of those values potentially inherent in the course of qualitative analysis.
