The TEACHING of MICROCHEMISTRY* GENERAL AfICROCHErNISTRY
A. A. BENEDETTI-PICHLER Washington Square College, New York University
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ICROCHEMISTRY deals with the systematic presentation of the technic used in the performance of chemical experiments on an essentially smaller scale than is usually employed in the chemical laboratory. In general, one may assume that 10 to 50 mg. represents the upper limit of the amount of material used in microchemical work, while 0.0001 mg. is a t present to be considered as the smallest quantity of material which may serve as the object of a microchemical investigation. It is obvious that the technic of working and the methods of observation 'must vary with the quantity of available matter. Microchemistry has already contributed greatly to the progress of science, but one cannot expect it to do its proper share before the majority of research men (archaeologists, biologists, chemists, geologists, etc.) are informed as to the possibilities of microchemical work. Specialized courses taken by experienced scientists serve, of course, for the dissemination of the ability to work with small quantities of material. It is, however, even more important to provide for the future generations of scientists a general introduction to microtechnic, which will enable them to decide on the possibility of continuing research work on small quantities, and on the probability of success in doing so. Those of them who possess inclinations to this type of work and have the required imagination will also be able to develop the methods needed for the solution of their problems, and will do so with special success as they themselves understand better than anyone else the requirements of their own research. T o serve the purpose just outlined, an introductory course in the micro-technic of chemistry mnst have the following features: (1) as many as possible of the important and generally applicable working methods must be practiced by the student; (2) working methods applying to various quantities of material must he taught and the student must be brought by practical experience to the realization of the mperative necessity of closely correlating the technic, the sizes of the vessels, and their surfaces to the quantity of material to be handled at any stage of the work; (3) the student must work out problems (unknowns) which require the correct application of this knowledge. Lastly, the course has to include a thorough, practical introduction to low-
power microscopy if the student does not possess this knowledge already. Furthermore, emphasis should not be laid in such introductory courses on the training of efficient, expert microanalysts, nor should the importance of the sensitivity of the tests and procedures he exaggerated. The most important thing here, as in science everywhere, is to obtain reliable results, and to check them by the application of a larger number of reliable methods. Teaching experience has furthermore shown that such courses present a unique possibility from a purely educational viewpoint. Professor W. C. MacTavish, Administrative Chairman of our Department of Chemistry, authorized me in 1931 to give an introductory course in microchemistry to the undergraduate students. Up to date nearly 200 students have enrolled for this course. I am, therefore, able to speak from experience and to support every one of the foregoing and the following statements without reservation. Erroneously, the improvement of the general working technic is often attributed to the acquirement of some mysterious skill in the performance of experiments with small amounts of material. However, the most skilled human hands would he too clumsy to conquer the world of small dimensions were it not for the mind which provides them with the proper tools. Actually, the improvement in working technic is due to the fact that chemical work on a small scale enforces the acquisition of the scientific attitude that reason mnst determine every action, an attitude apparently so strange to human nature that it is rarely adopted merely on the advice of a teacher. In working with small quantities of material, however, the student is continuously compelled to give every operation careful consideration as to the proper choice and use of apparatus. AS a rule, thoughtless working or incorrect decisions will result immediately in complete loss of material, and thus render continuation of the experiment impossible. This enforced mental concentration on the problem a t hand is the real factor which lends distinction to the work from a purely educational viewpoint. We have also shown, by example, that such introductory courses can he organized without great expenditure. The reagents and various small apparatus necessary cost less than the ordinary equipment given to * Presented at the symposium on Recent Advances in Micro- students of chemistry. The only item which is worth chemical Analysis before the Division of Physical and Inorganic mentioning is the cost of microscopes, However, one Chemistry (Section B, Analytical Chemistry) at the eighty-ninth meeting of the American chemical society, p~~~ york city, ~ ~ C ~ O S CisO sufficient P ~ for two or three students, and April, 1935. only the most inexpensive microscopes (obtainable from
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good firms for about forty dollars) are required. Only magnifications of 30X and SOX are used, thus eliminating the necessity of condenser and fine adjustment. The stand should be rugged and should possess a highquality rack and pinion for coarse adjustment, and a mirror which can be swung from left to right. Microbalances are not required, since there is no necessity to include quantitative work in an elementary course. A. A. BENEoerrr-1'lcHl.c~A N D W. I:. S P I K ~"Introduction S, to the microtechnique of inorganic qualitative analysis," hlicrochemical Srrviee. I)ouglastun, I.. I., x. Y . , 1935.
A text* suitable for undergraduate students as well as for self-instruction has been prepared, which permits individual work of the students and reduces the work of the instructor, even with large classes, to some occasional suggestions. Motion pictures demonstrating the elementary procedures from the viewpoint of the experimenter himself are available, and may be used to speed up the work of the students. It hardly needs to be mentioned that the author and his co-workers will be glad to assist in the organization of courses in general miaochemistry.
