Chemical transport and zirconium - Journal of Chemical Education

Draws attention to a recent paper that discusses the purification of zirconium by the Van Arkel filament method. Keywords (Audience):. Upper-Division ...
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The problem doesn't seem to be how science is taught but what it seems to be. Many of the students argue that all of this effort in the teaching of science is being directed toward introducing the true meaning of science and its method to the nonscience student. At the same time, say these students, the scientist himself is incapable of any hut the emptiest platitudes when he strays from his own specialty. His statements are vague generalities: to render human nature more beautiful, nobler, and more harmonious; to assure the triumph of peace, liberty, and reason; to eliminate the cultural lag. At the same time, however, it is impossible to have confidence in men who lack the faculties of criticism, discrimination, judgment, and option. It may be that the scientist has opted for arrogance a t the expense of that other ingredient, humility. Perhaps it will be concluded that man must strive for more than Seahorg's Post Office, reclamation project, and a science laboratory as an integral part of every state. When the social sciences, the humanities, the heritage of man's spirit, and the flourishing state of Twentieth Century science all work together, only then will the imbalances of each one he corrected and the vigor of each enhanced. Science must address itself to the problems of society in ways other than mere statement of the second law of thermodynamics. Young scientists must be made to realize a h a t has been the philosophy and history of science, what science can do, how far it can lead us, and what it is that makes science a cultural force. The scientist must be involved and make the nonscientist aware of this involvement. One of the students quoted Joseph Wood Krutch who said, "(He) is willing to consider the possibility of man being saved from the present perilous state by philosophy, religion, sensibility, or anything that depends upon the free functioning of the human intellect and spirit. Rut (he) will not be saved by propaganda, manipulation, and conditioning. These latter techniques can only t.ransform us into well behaved puppets; that would not be salvation but thc damnation of an eternal death."

Chemical Transport and Zirconium

To the Editor: With reference to the recent article in THIS JOURNAL^ on "Chemical Transport Reactions" I would like to draw attention to a very recent paper2 which discusses the purification of zirconium by the Van Arkel filament method. Until recently the maximum observed in the rate of deposition of zirconium has been thought to be due to the formation of involatile lower iodides, which reduced the concentration of halogen in the gas phase, thus lowering the rate of deposition of metal via zirconium tetraiodide.

It now seems likely that the mechanism causing the maximum is a change in the pressure dependency of the iodine diffusion coefficient. At low temperatures the rate of metal deposition is proportional only to the pressure of iodine at the filament, but as the temperature rises, the rate becomes proportional to the total pressure +t the filament (iodine plus zirconium tetraiodide). This suggestion is important in that it uses a simple mass transfer explanation instead of a relatively complex chemical one, particularly since the conditions required to produce the lower iodides3 are far removed from those used in the Van Arkel process.

Negative Catalyst

T o the Editor: I n the July issue of THIS JOURNAL (45, 477, (1968)), J. A. Young and J. G. Malik, in an answer to a chemical query regarding the difference between a negative catalyst and an inhibitor, explain that "the negative catalyst would be like an inert substance, substantially ineffective." This conclusion of the aforesaid authors seems to be based upon the mechanistics of the action of a catalyst which they have invoked in order to differentiate between a (positive) catalyst and a negative catalyst. Thus they conclude that "a negative catalyst would be a substance which when present in a reacting system provided a new path for the formation of products from reactants, but which path has a higher energy of activation than the energy of activation for the reaction mechanism which takes place between and among the reactants alone. So a negative catalyst would not slow down a reaction; the reactants would merely react to form products in the same manner, in the presence or absence of such a negative catalyst." Although there seems to be no inconsistency in the arguments of Young and Malik, their mechanistic (and not the prevailing phenomenological) approach is liable to cause some confusion. For example, according to Paul H. Emmett ["Encyclopedia in Chemistry" (2nd ed.), Editors: CLARK,GEORGEL., AND HAWLY,GESSNER G., Reinhold Publishing Gorp., New York, 1966, p. 1871 "One common theory of the action of negative catalysts is that they combine with and remove from the system traces of positive catalysts, or they combine with intermediates in a chain reaction in such a way as to break the reaction chain" which will obviously result in the retardation of the reaction. Identical views have been expressed by E. Abel ["Proceedings of the International Congress on CataVolume 46, Number 3, March 1969

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