2118
JOURNAL OF CHEMICAL EDUCATION
SEPTEMBER, 1930
subject will prove helpful. For example, to explain unsaturated phenomena we can refer to the work of von Baeyer, Victor Meyer, and Thiele; in the field of stereoisomerism we can point to Pasteur, van't Hoff, and Le Bel; and for the elucidation of the structure of benzene we have Kekule and Holleman. More recently there has been developed, largely through the researches of W. A. Noyes, Stieglitz, Fry, and Kharasch, an electronic theory of valence t o explain such unrelated properties as the strength of acids, the addition reactions of unsaturated compounds, molecular rearrangements, and substitution reactions in the benzene ring. Some teachers have questioned the wisdom of introducing the first-year student to electronic interpretations, but modern texts are devoting more and more attention to this subject, and i t has been the experience of the author that when the subject is treated in the light of G. N. Lewis' ideas of polar and non-polar bonds the student receives a clearer insight into the mechanism of organic reactions than he can derive from any other source. In conclusion we shall mention two other ways of helping the student understand organic reactions. One of these is through the study of residual or secondary valence forces. In the slow molecular reactions of organic chemistry intermediate compound formation plays a leading r81e. Werner's ideas of residual valence are being applied increasingly to the elucidation of organic reactions, and evidence is being disclosed for the existence of intermediate compounds in many types of reactions. As a concluding suggestion, the student may be pointed to the growing literature on the applications of physical chemical methods t o the study of organic reactions. These methods are being applied from many angles, but all the research has as its ultimate objectives the determination of the distribution of valence forces within an organic molecule, and the method by which these forces are brought into play during a chemical reaction. This investigation into the quantitative side of organic reactions has already shed much light upon the mechanism of the reactions, and it can be used to advantage in increasing the respect of hlast-furnace superintendents, cast-iron pipe foremen, and physical chemists for the science of organic chemistry.
Light Limits Visibility of Atom. Man will never be able to look distinctly at an atom, according to Prof G. P. Thomson, English physicist. Even if apparatus is developed which might enable man to enlarge the vision of an atom to a point where his eye might see it, he would perceive only a blur, for he would be looking at an atom in motion. The electrons, of which we conceive atoms to be composed, would be knocked about, largely by light rays. A ray of light is thought of as a delicate thing, but when light reaches so small a thing as an atom it no longer is delicate. It gives the atom a severe poke. Thus light itself becomes a harrier which limits viaion.-Chi Beta Phi
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