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unsatisfactory. It would have been helpful if the author had given the analytical data for the preparations which he used. The German literature contains directions for purification, for example by R. Scharf [Z. physik. chem. Untem'cht, 47, 202 (1934) 1. A still better purification method has been developed by L. Doermer, which will appear in the new (6th) edition of "Technik der Experimentalchemie."
To the Editor: Lecture demonstrations are extremely effective teaching devices. Indeed, their pedagogical soundness is hardly debatable. As Dr. Rakestraw once said of the practice: "I can scarcely imagine proceeding without it." I don't suppose a single teacher exists who does not use demonstrations in his teaching. In some setups a vast array of demonstration equipment is available and special staff is on hand to set it up. Now what happens? The usual procedure is well known. The experiment is set up, either by the teacher himself or by his demonstrator, and wheeled into the classroom. With a semblance of drama the routine is run through. (Note, please, that this drama is a very necessary ingredient and too few teachers possess it!) The instructor gives some discussion appropriate to the experiment, sometimes asks if there are any questions (this invariably not often enough), turns to the blackboard and takes up his lecture. The bell rings, the class goes, the equipment disappears. The episode is closed. Only rarely does any discussion ensue among the observers. It is reasonably safe to say that little
JOURNAL OF CHEMICAL EDUCATION
of the experiment was understood by the majority of the students. How do I know? I have asked students to explain or describe to me wbat went on, and why it did, and I find they can't! If the demonstration is exciting or intrinsically dramatic the student is entranced and he goes away with great wonder, hut this is no guarantee that he is instructed. Can we improve this situation? For several years I have resorted to a scheme in physics which has shown itself to be instructionally sound. I believe the device can be profitably used by chemistry teachers. I require the student to write up the demonstration expwiment. This he does in a bound notebook reserved for these write-ups alone. He gives it a title; he recites the procedure in his own words; he describes what was done, what happened, and why. Some students do an astonishing job; some give an historical comment, if one is appropriate; some carry the experiment to interesting extensions. But in general the write-ups are shamefully inadequate. Most of the people do not know what was going on! Apart from this, the linguistic performance is astonishing. Students cannot write acceptable English. This device, then, is good practice--a practice sorely needed. I read the reports critically. This is a chore and a travail. But it is informative to find how much (or more often, how little) of what I said and did took root. By this device the student has exercise in formal exposition. I learn how to improve my demonstrations. Obviously, the student is now under compulsion to watch the demonstration critically, and when he writes it up some critical thinking is demanded.
JULIUS SUMNER MILLER UNIVER~ITY OF CALIPORNIA CALIFORN~A Los ANGELES,
