THE IMPORTANCE OF ELECTROCHEMISTRY IN THE TEACHING OF ANALYTICAL CHEMISTRY* N. HOWELL FURMAN, PRINCETON UNIVERSITY, PRINCETON, NEWJERSEY
The remarks that come to mind under the above title might equally well be called the importance of analytical chemistry in the teaching of electrochemistry, for the purpose of this paper is to consider two questions first, how much of the field of electrochemistry is included in other standard undergraduate courses in chemistry; and second, what is the relation of electrochemistry to courses in analytical chemistry. At Princeton, as in many other colleges and universities, there is no formal undergraduate course in electrochemistry, although an excellent, theoretical, and practical graduate course is offered. Nevertheless a substantial part of the theory of elect roc he mist^, together with representative laboratory experiments, is included in the courses as they are a t present organized. In the introductory courses in general inorganic chemistry the theory of electrolytic dissociation is considered, and some simple qualitative conductance experiments are performed by the students. Electrolytic preparation methods are discussed, and some of the broader aspects of electrochemistry are considered. Naturally the discussion of technical electrochemical methods is brief and elementary. In the courses in qualitative and quantitative analysis the application of the law of mass action to ionic'equilibria is considered in some detail, with representative problems. Oxida~on-reduction reactions are considered from an electrochemical viewpoint. The subject of electroanalysis is entered into fairly thoroughly. The relation of certain other electrochemical topics to analytical processes is discussed in connection with the coagulation of colloids, choice of indicators, etc. In the physical chemistry courses there is a considerable proportion of theoretical and experimental electrochemistry, includingionic equilibria, conductance, and potential measurements, together with their various applications. The electrical behavior of solids, liquids, and gases is considered. The principles of electrochemical processes, as applied to preparative work, are illustrated by certain experiments in the courses in advanced inorganic and industrial chemistry. Students who desire to try the electrochemical preparation of certain organic compounds, are permitted to attempt such work in connection with their courses in organic chemistry, or as an optional project. At present no work of this kind is required in these courses. * Presented before the Fifty-fifthGeneral Meeting of the American Electrochemical Society, held at Toronto, Canada, May 27, 28, and 29, 1929. 62
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Without going too much into detail the writer estimates that about 80 per cent of the material that is included in a representative book on electrochemistry, as for example "Electrochemistry," Volume I, Creigbton and Fink, Wiley, is dealt with in the present undergraduate courses. Furthermore, in their upper-class years our students are required to elect only four courses, and spend the time thus released in independent study under the supervision of some member of the faculty. A considerable number choose fields of study which involve some electrochemistry. Practically all of those who work under the writer's direction study potentiometric titration methods, pH measurement (electrometrically and with indicators), and other electrochemical processes, as, for example, eIectrodeposition methods. I t is interesting to note 'that a somewhat similar plan of independent study is used in certain foreign institutions.- For example, at the Eidgenossiche Technische Hochschule, Ziirich, in the final year the chemistry students in connection with the "Diplom Arbeit," devote a certain amount of time to more or less independent study of analytical processes, under the guidance of Professor W. 33. Treadwell. Recently the majority of students have worked in the field of potentiometric titration. Rather difficult problems are attacked. For example, one student studied the use of the electron tube voltmeter in a variety of typical titrations, which had been studied previously: he then studied new titrations, which involved the use of sodium hydrosulfite with rigid exclusion of air. A very creditable orientation study of the problem was made in about five weeks of intensive work.' At other institutions, which offer no formal undergraduate course in electrochemistry,there is in general a substantial training in this field that is supplied by the other courses. Let us consider the fields of electrochemistry that are especially important to the analyst and in which analytical chemistry can give valuable training. At present it seems desirable to attempt in analytical courses, to emphasize the application of the law of mass action to certain types of ionic reactions, and to introduce representative calculations, and lecture experiments illustrating common ion effect, etc. Mention should of course be made of the activity concept. At present, however, it seems desirable to present in a simple manner the principles that apply at least as a good first approximation in the sensitive end-point regions, which are of chief interest for qualitative and quantitative analysis. I n our courses in quantitative analysis in connection with electroanalysis we include a review of the laws of electrolysis, consider overvoltage effects in an elementary way, and discuss the possibilities of elec-
' The writer had oppartuoity to make observations while working as a guest in Professor Treadwell'slaboratory, Oct., 1927-Jan., 1928.
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trolytic separations in general. In our new chemical laboratory now nearing completion, there is a special room for electro-analysis and related analytical methods; it is planned to have apparatus available for following potential changes a t the anode or cathode during electrolysis. Frequently a few electro-analytical determinations stimulate our students to read not only the theoretical sections of Classen-Hall's book, for example, but even to read more broadly in the field of electrochemistry. Most of them inquire into the sources of current, and revise their early conceptions of the e. m. f. series. Some students have studied Frary's magnetic stirring device. Although electro-analysis, in the opinion of one foreign worker who has many contributions in this field, "now belongs in the museum class" of methods, that is, appears to be substantially complete, most students profit much from experience in this field of study. . The theory of volumetric analysis rests on an adequate foundation, in our opinion, only when it is discussed throughout from an electrochemical viewpoint. To quote, "If a system is in mobile equilibrium it is relatively easy to formulate the mathematical discussion of the possibility of a titratiou, to find the optimum working conditions, and to calculate the titration o r . . A new method does not need to be developed purely empirically, it may generally be deduced theoreti~ally."~ The foregoing statements appear to have been justified abundantly through the amazing development of electro-titration methods during the past decade. The study of even rather elementary volumetric determinations may be made to contribute much to the student's understanding of ionic reactions and equilibria. It is difficult to discuss the titration of a weak acid with a strong base, or vice versa, without some consideration of the electrochemical principles which govern the hydrolytic equilibria and the corresponding choice of indicators. When methods that rest upon other types of ionic reactions are considered, the electrochemical viewpoint is found to be very serviceable in picturing the course of the reaction in question, and in deciding as to the limitations of the method, the possibilities of indicator action, etc. The electronic viewpoint of oxidation-reduction reactions appears to be useful to students in mastering the more difficultprocesses. A clear understanding of the usual types of volumetric methods serves to unify the whole field of ionic reactions. If some potentiometric and conductometric methods are included in the study, the electrochemical viewpoint becomes even more serviceable, and many theories and experimental facts are correlated in a clear fashion. The author has previously a
1928.
I. M . Kolthoff, Volumetric Analysis, Vol. I, viii, John Wiley & Sons, New York,
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discussed the usefulness of potentiometric titrations as a means of studying electrochemical principles.* In the symposium upon the teaching of physical chemistry a t the 76th meeting of the American Chemical Society a t Swampscott, Mass., September, 1928, the idea was expressed that certain topics formerly dealt with in physical chemistry courses might profitably be transferred to analytical courses; in particular potentiometric and conductance determinations and certain other electrochemical topics were specified.' The writer is in accord with this view, especially in connection with electrotitration methods. Differences in educational policy, personnel, and equipment will in specific instances determine whether i t is advisable to give a formal course in electrochemistry, or to distribute the subject matter among other courses. The essential thing is that the students .shall receive opportunity to study and experiment with electrochemical methods. Many excellent electro-titration methods have been devised in the electrochemical laboratory of the Technische Hochschule, Dresden, for example, while a t other institutions, e. g., Utrecht and Ziirich, important contributions in the same field, as well as in other branches of electrochemistry, have emanated from the analytical laboratories. Much of the recent development of analytical methods is directly traceable to advances in understanding of electrochemical principles. Present trends seem to indicate that the electrochemical viewpoint will be outstanding in the teaching of analytical chemistry in the coming decade, and conversely that the teaching of analytic# chemistry can be of increasing importance in giving fundamental training in certain branches of electrochemistry. THISJOURNAL, 3, 932 (Aug., 1926). Cf. V. K. LaMer, I h d , 6, 263 (Feb., 1929).
