FC103 Hazard
T o the Editor: With reference to the article by Clay fii. Sharts in THIS JOURNAL 145, 190 (196S)I in which ,the author states that "FC103 is a potentially hazardous reagent and may explode with some organic compounds" we think that our experiences may be of interest. We had frequently used this reagent without incidents and thought that our safety measures were adequate until the day when the following-mixture was chosen: 17-hydrazone of 5.0-androstane 3a-hydroxy 11, 17-dione (1 g), methanol (36 ml), water (4 ml), and FCIOa (2 ml). At -6.i°C a violent explosion occurred which destroyed the whole hood, split the 10-cm thick concrete bench, shattered two superimposed security glass shields, and severely injured two persons, one of whom lost an eye. A number of similar trials have since been carried out in a casemate but no further explosions have occurred. G. NOMINE G. MULLER
Pollution from Chemistry Laboratories
T o the Editor: What becomes of the fluid wastes from chemistry laboratories? A lot of waste, especially from organic laboratories, may not be readily biodegradable, and it can contribute significantly to the problem of keeping local bodies of natural water clean. Oily materials, dyes, and strong reducing agents present problems. I n the organic chemistry laboratory at Yale University a number of used 5-pt acid bottles were strategically placed around the laboratory and marked ORGANIC WASTES. The students were asked to cooperate and to pour their waste organic liquids into these bottles. The response has been good. When the bottles become filled, they are capped securely and disposed of as solid trash, and replaced. This method of disposal is less than ideal in a mechanized trash truck. Other and better methods must be used elsewhere. The writer of this letter will be glad to hear how others have met this problem and to report a summary.
Fused Salt Investigations Needed
To the Editor: It was my privilege to have had a lifetime career of teaching chemistry at both high school and college levels. After retiring from active college teaching, I find myself acting as consultant on a data collection project. As I look back, I can see that it would have been very much to my advantage and helpful to my students if I could have had this current experience earlier. (On the other hand, the teaching background seems quite necessary for a proper perspective on my current assignment.) As an undergraduate and graduate student, I used to wonder how a teacher would select research topics for us. Just searching the literature on a chosen subject required an amount of time which was simply not available. In fused salts, now my particular field, this Information Center simplifies the problem as the search and compilation of data continues. (Physical Properties of Fused Salts, SC-R-68-1680.) Scarcely a day goes by that I do not find "holes" in the data which need investigation. Many discrepancies appear in comparing reports from different contributors or sources ~ ~ h i c h , though I am rather separated from active laboratory work, I have an urge to check for myself. Many fused salt problems which still need investigagation aould not require elaborate equipment, and much ~ ~ o could r k he done at the undergraduate level to the great advantage of both the student and the literature. Such subjects as melting point diagrams, heats of fusion, heat capacities, conductivities, vapor pressures, and densities of mixtures could be considered. I would welcome correspondence with teachers who are looking for such problems. Perhaps we could he of mutual help and, at the same time, contribute also to chemical information.
Teaching the Transition Elements
T o the Editor: Dr. Quagliano's response to the question [THISJOURNAL, 46, 227(1969)] on the relation between the definitions of transition elements and the zinc subgroup metals was excellent in depth and scholarship, as might he expected. I feel, however, that one aspect of that answer d e serves more emphasis; the teacher who reads the answer Volume 46, Number 5, Moy 1969
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may wonder which of the definitions of transition elements he ought to offer to his students. I suggest that the approaches and implications to teaching might be stressed, in connection with that answer, in the following way. The definition of transition elements, or any other definition, for that matter,may be solely operational or solely conceptual or a combination of both. I n any event, the definition depends upon a model and thus carries the strengths and limitations of that model. This point in particular, it seems to me, should be presented to students in the classroom. Further, for example, when in any single instance such as when a discussion of the definitions of transition metals is presented, parallel comparisons to other multiple definitions and their appropriate models ought to enhance the learning process. I n my teaching of high school chemistry, I have found it convenient to list all the elements between Groups I1 and 111 as transition elements. This makes a neat package as far as the Periodic Table is concerned-a kind of operational approach. Limiting most of my teaching to the scandium row, I point out the properties common to the ten members of the row. These properties include metallic nature, possession of multiple oxidation states (except zinc), formation of colored ions (generally) and ability to form complex ions. This completes the operational approach, enhanced, where possible, by suitable experimental work. The conceptual approach then follows to tell why this behavior is characteristic of the transition elements. Here we stress the filling of the next-to-the outermost energy level, that is, in the scandium row, the use of 3d orbitals for bonding. Since zinc is somewhat atypical, I point out that it may or may not be considered a transition element. Some of its properties (complexing) resemble the general properties of transition elements but our model of this behavior, like all models, is limited. This, I feel, is a sufficient picture for both terminal and science-oriented students.
course, i.e., mechanisms of reactions involving carbonyl group cont.aining compounds requiring the postulation of t,ransition states in which carhaniori charge dclocalization is required, even though the inclusion of heteroatom effects was not explicitly dealt with. Student interest in the mat,erial was evidenced hy several indicators: participation in class and individual library research in particular. A set of notes based on my lecture notes wa,q handed out near the end of the series of lectures. The student.^ were teste! hy the assignment of a take home examination a t the conclusion of the Iecturc series. They were asked to calculate the h20 energy level diagram for the cation, free radical, and anion of methylenecyclopropene and to discuss the relative stahilitics of the three species in terms of resonance energy. They were also required t,o calculate the electron density, charge density, bond order, and free valence for the molecule. The student response on the t,al
