Demonstrations vs. Chemistrv Laboratorv J for Freshman Engineers SAUL B. ARENSON University of Cincinnati, Cincinnati, Ohio
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T THE University of Cincinnati there are five how to make T-tubes, how to put side arms on flasks, elementary courses in general chemistry given to how to work pyrex glass, why hard glass cannot be students in: (a) liberal arts; (b) evening col- sealed on to soft glass, how metal wires are inserted in lege; (c) business administration; (d) chemical en- glass, etc. gineering, and (e) all other fields of engineering. The "So you expect the student to be able to duplicate subject of this paper is the course (e) given to freshman that expertness, having seen it done?" asked someone non-chemical engineers, and has nothing to do with during a discussion of this plan. In the h t place, the any of the others. students seeing this demonstration are never going Up to three years ago, that course was a conven- to do any glass bending unless these non-chemical tional orthodox course, consisting of four to five lectures, engineers get a job making neon lamps-which is quite a three-hour laboratory period and a one-hour quiz unlikely. In the second place, even if they had persection per week. At present the lecture and quiz formed the simple experiments themselves, they section hours are still unchanged but the three-hour couldn't classify themselves as experts. What these laboratory period has been changed into one-hour students are learning, among other things, is an apdemonstrations late in the afternoon on two days a preciation of what has to be done to glass by the glass week. worker-what can be done and what cannot. CerThese demonstrations are not the simple ones per tainly those students who are going on with chemistry formed by the teacher during the regular class hourneed the experience of glass bending, preliminary to those are still part of the lecture routine. Nor are their courses in organic and physical chemistry. But they necessarily the same experiments which the why do these non-chemical engineering freshmen student would perform in the laboratory. The easiest need to burn their fingers making glass bends? way to explain them is to give a few examples. Some more examples: To illustrate specific gravity, An experiment found in practically every labora- the student is shown various pieces of apparatus, tory manual involves heating KClOa and MnOz, and ranging from simple apparatus to that used in physical testing the O2 thus made. That is practically a repe- chemistry research. He gets acquainted with specific tition of what students have seen their lecturer do, gravity spindles, hydrometers, pycnometers, Westphal during lecture hour. But one of our experiments on OX balances, and other instruments, and recognizes their accuracy and usefulness. .. to the engineers consists in a demonstration-usually To emphasize viscosity, various viscosimeters, from a spread out over two or three periodsshowing the use of O2 in the determination of the calorific value of a coal pipet on up, are brought into the demonstration room. sample. During that demonstration everything is done Samples of oil are run on a "Saybolt" under varying except the firing of the sample. The bomb is loaded, conditions of temperature. That certainly should the apparatus assembled and explained, and typical emphasize the principles of viscosity needed by an time-temperature data are given. Th$stndents, having engineer. Many of the experiments are quantitative in nature inspected the apparatus, having looked through the telescope a t the mercury level in the Beckmann ther- and most of them, with preliminary preparation by mometer, then draw a timetemperature ignition curve the instructor, can be performed in twenty minutes, during the demonstration period. Finally, they cal- leaving a half hour for discussion, calculating results, culate the calorific value of the coal in B.t.u./lb. and and evaluating the data. To get the students to appreciate the work of the cal./g., making, of course, all necessary corrections. Not only that, but they are given data on another coal analytical chemist, and to teach them the principles of sample and are required to find out which sample gave normal solutions a t the same time, the following are demonstrated : more B.t.u./dollar. Likewise the calorific value of a gas is demonstrated. (a) Per cent NaOH in lye ( b ) Per cent NarC08in soda ash (two ways) These experiments should give to non-chemical engi( 6 ) Per cent Fe in iron ore neers a better appreaation of the work of the chemist (d) Per cent 1%in tincture of iodine and chemical engineer. Per cent Cu in ore (an indirect determination) (6) The usual experiment performed by students on glass (fl Per cent N in a fertilizer (Kjeldahl) bending involves making a wash bottle and getting it To emphasize the principle of fractional precipitaapproved. For our demonstration on glass working, a tion, a titration is run determining the per cent of NaCl graduate student or faculty member who is an expert by the Mohr method. glass manipulator demonstrates the simple thinm about Not only are some of the nicest ex~eriments of auanglass bending. Then in the rest of the period he shows titative analysis run as demonstrations, but the cream 241
of the physical chemistry experiments is likewise stolen. Usually the experiments are first performed with relatively simple apparatus, such as freshmen themselves could handle. The errors involved in the use of the crude apparatus are discussed, then the real physical chemistry apparatus is introduced to show the refinements. The principle is put across by the simple experiment, so that the students will not lose sight of the fundamentals involved because of the multitude of complicating details in the daborate apparatus. An experiment in photography can be performed, in a semidarkened room, doing everything except the development of panchromatic film. Intensifying, reduction, making of blue prints-all of those are processes of interest to the average freshman engineer.
There are many reasons for this sort of change from laboratory to demonstrations. Many teachers believe that, per hour of teaching, laboratory instrnction is a very inefficient method. No matter how you try to influence students to ask questions of the laboratory assistants, they always get a great deal of their information from their neighbors. In our demonstrations, the faculty lecturers answer the many questions. The trouble of checking in and out of laboratory is eliminated. The lessened number of students taking laboratory avoids congestion a t the stockroom window. Even the saving of chemicals is no small item. But the main purpose, let me repeat, is better instruction in the way that it will do this type of student the most good.
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