teaching
I
Film Reviews
W. ROBERT BARNARD Evergreen State College Olympia, Washington 98501
Bromine:
Element from the Sea
Modern Learning Aids, A Division of Ward's Natural Science Establishment, P. 0. Box 302, Rochester, N. Y. 14603, for CHEM Study. 22 min, 16 mmsound, color. This film presents, in heuristic fashion, the development of an industrial procesq for concentration of bromine from sea. water. I t leads the student to an understanding of the kind of thinking which must he done in order to convert a knowledge of laboratory phenomena into useful, practical processes for the chemical industry. Finally, it shows a chemical plant designed for separation of bromine and makes note of the correspondence between large-scale process units and labomtory demonstrations done previously. The results is an interesting and informative film. To begin with the film demonstrstes the reactivity of bromine toward phosphorus, hydrogen, and aluminum. No ohemicd equations are given, but the names of all products are mentioned and the demonstrations me done quite well. Proper safety precautions in the handling of liquid En,such as rubber gloves and ventilation, are emphasized. The reactivity of bromine and the solubility of the reaction products shown in the demonstrations m e associated with the occurrence of bromine as bromide salts in the oceans. Next the film leads one to a closer examination of the solubility of hromine in water. The relatively small solubility of hromine and the deeolorising effect of base are demonstrated, and an equation is given. The reversal of this equilibrium by acid is tested as a means of removing bromine from concentrated sea water, hut no color is observed, indicating that hypabromite is not available. Next a suitable oxidizing agent for bromide is sought with the aid of a table of E' valoes. This discussicin will probably he somewhat confusing to the student who has not yet studied
ocem
Scene illustrating the uro of chlorine to remove bromine from water, from the Rlm "Brdmine: Element from the Sea."
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Figure 1.
Journal of Chemical Education
electrochemistry, as will the kinetics-based explanation of the fact that oxygen will not work even though the E" value says it should. Chlorine also has a suitableES and huhhling Cb through the concentrated sea water produces rad-brown hromine (see Fig. 1). The final problem involves concentration of the bromine which has been swept out of the solution in a stream of air. Demonstrations show that the bromine can be reduced with SO1, dissolved in a small quantity of water as HBr, reoxidised and steam distilled to give reasonably pure Brz. The same sequence of reactions is then followed in an industrial plant, starting with sea water and ending with liquid hromine ready for tank car shipment from the plant. This film would be excellent as a finale to the study of the halogens. It shows clearly that knowledge of descripiive and some physical chemistry is necessary in the design of industrial processes which produce useful products. JOHNW. MOORE Indiana Universil~j
Chlorine:
A Representative Halogen
Sutherland Educalional Films, 201 North Occidental Blvd., Los Angeles, Calif. 90026, far Manufacturing Chemist's Association, 17 min, 16 mm, sound, color. The selection of chlorine as a representative of the halogens is a reasonable one, and an attempt is made to show that its chemical properties closely resemble those of the other halogens. As an introduction the natural abundance of chlorine (11th in the crust of the earth, mostly in sea water), and the fact that commercially it is the most important of the halogens are mentioned. Following this the electronic structure of atomic chlorine and the fact that it consists of diatomic molectlles are discussed. The eenersl method of ~ r e ~ a r a t i oof n chlorine by nrrim of n *tn,ugux~diringnzmr
