Die Homoopolare Bindung. Eine allgemein ... - ACS Publications

Die Homoopolare Bindung. Eine allgemein anwendbare Elektrontheorie der Valenz (Hahn, Georg). E. A. Wildman. J. Chem. Educ. , 1935, 12 (6), p 300...
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it is, however, of interest t o note that Dr. Stephanides' views are quite in accord with those of Dr. Hopkins, save that he places the beginning of alchemy in the Egyptian temples several centuries before the founding of the Alexandrian school, and evidence t o support such theory is given. Dr. Hopkins' book is written in an easy, readable style, notwithstanding the accumulation of the material from such an enormous number of sources which makes arrangement extremely difficult. It should appeal not only to those for whom the history of chemistry is of special concern, but also to all who have an interest in the development of thought. NICHOLAS D. CHERONIS THBSYNTB&T~E~L LABOXA~OOIBS

Cmuoo, l ~ ~ r ~ o l s

COMPREHENSIVE UNITS IN CHEMISTRY with Experiments, References, Workbook Exercises and a Testing Program. F. F. Carpenter and R. H . Carleion, instructors a t Roosevelt High School, Dayton. Ohio. J. B. Lippincott Company, Chicago, 1935. xvi 420 pp. (detachable) 24 pp. of tests bound separately. 73 figs. 19.5 X 27.2 cm. $1.20 postpaid.



The authors daim the following advantages for this omnibus volume: 1. Meets the need for economy; 2. Is effective in handling large classes; 3. Recognizes individual differences; 4. Overcomes distaste for old style textbook study. The hook has been tried out in mimeograph form. It meets the requirements of standard curricula. The book is based upon the Morrison nnit-problem plan of organization. A typical unit includes: 1. Questions for review and recall; 2. Viewing the whole unit; 3. Unit problems to he solved; 4. Solving the unit problems, (a)Introduction t o the problem. (b) Experiments, (c) Demonstrations. (d) Textbook references, (c) Exercises, (f) Summary; 5. Material for enrichment. (a) Optional demonstrations. (b) General references, ( 6 ) Projects and reports, (d) Field trips, (e) Visual aids; 6. Vocabulary, summary questions, self-testing exercises: 7. Mastery tests; 8. Remedial work and re-test. The units are as follows: 1. The point of view of the chemist; 2. The nature of matter; 3. Solutions and near solutions; 4. Chemical action in solution; 5. The chemistry of electrolytes: 6. Chemical equations and calculations; 7. Sulfur and its compounds; 8. The halogens and the periodic law; 9. The nitrogen family; 10. Mineralogy and chemistry; 11. Metallurgy and chemistry; 12. Organic chemistry. This book contains 80 valuable drill exercises. 51 laboratory exercises, 30 demonstrations, and references which adapt its use to any of ten popular high-school texts. A well-selected set of references OF CH~MIWLL EDUCATION is included ~-~~~~~~~to the TOURNAL with cnch unit. The questionr illelude bhe completion, multiplrchoice. and matching type. Limited opportunity is given for pupils to erpreg? rhetnselvcs in complete sentences. Bring bared on textbwks now used, the ionization theory is according t o Arrhenius, plus the addition of the electron transfer idea. The electrolysis of water is based on the discharge of the SO4-- ion. The hydrolysis of NalCOs is simplified to avoid introducing the HC08- ion. Types of chemical reactions include the traditional double displacement. The introductions to the units are interesting and arouse curiosity. The laboratory experiments will fit any standard collegepreparatory course. A warning about avoiding any reverse flow of gas in the train on p. 237 could be included as a safety precaution. The emphasis on mineralogy will have an appeal to a limited few in any class. The inclusion of a brief introduction to elementam crvstalloeraohv " . . coincides with the oro~hecvfound keports the chapter on Crystallography in the 1933 of the London Scientific Society. The number of errors which have crept into this Z1/r pound volume is surprisingly low. P. 3 gives an incorrect equivalent for a liter. On pp. 10 and 34 the statement, "1 part of hydrogen and 15.88 Darts of oxygen combine to form hydrogen peroxide" is open to question. P . ~ contains O some confused wording about testing for iodine. One would suggest a connection between ~

atmospheric nitrogen and ammonia in the nitrogen cycle diagram onp.271. The authors have caught the spirit of idealism. "Today we look t o the chemists in our universities and industries for leadership in the quest for a life rich in its opportunities for service, and promising health, happiness. and prosperity in return." ELBERTC. WEAVER

DIE HOMO~POLARE BINDUNO. EINE ALLGEMBIN ANWENDBARE ELEKTRoNENmsoRrE DER VALENZ.Dr. Georg Hahn, Johann Wolfgang Gwthe-Universitit, Fradkfort am Main. Wilhelm Isensee. Frankfurt am Main. Germany. 1934. viii f 96 pp. 19 tables. 15 X 22 cm. 2.50 RM. This booklet is addressed to the organic chemist who is interested in valence theory. The hesitancy of German chemists t o concern themselves with electronic theories of valence until recently was due largcly ru the nrhitmry u3e and the insecure physical basis of the concepts, the author states. Suw that the rlrctron-"air bond of G. N. Lcwis has becn sufficimtiv justified by the wave mechanics researches of Heitler and ond don (19271929). ,. this idea mav be made the basis of a simole and eeneral " theory to account for the reactivity of organic compounds The fundamental physical postulates are: 1. Bound electron pairs are localized with respect to their vibrations by two adjacent positive fields. Both spin and orbital momentums are opposed. 2. Unbound electron pairs are in only one positive field, that of the atom kernel t o which they belong, and are free to move about within their energy level. They are opposed in spin but not in orbital momentum. 3. Single electrons are unbound also. They give the atom or group the character of a radical and are more free to move than the unbound pairs. Neither their spins nor their orbital momentums are opposed. Deformation of the electron shell of a carbon atom may be produced by a number of causes, whereupon it follows that one portion of the kernel becomes r4atively negative and another positive. I n consequence. the atom acts as an electron donor when a valence bond is established a t the negative portion and as an electron acceptor when it occurs a t the positive portion. The general criterion far determining the donor or acceptor character of other elements is the ionization potential, the elements a t the left of the first short period being donors and those a t the right, acceptors, if their fields are undeformed. However, the latter (N, 0 , F) because of .their free-moving unbound electron pairs, may act as donors t o deformed carbon atoms. Hydrogen is an acceptor toward elements of Groups I and I1 and a donor toward carbon and the elements of Groups V, VI, and VII. On the basis of these conceptions the author proceeds with considerable success to explain the behavior of twenty-four types of structure or reactions among organic compounds, including unsaturated groups and the conjugate system, the benzene .ring, ammonium salt formation, the Beckmann rearrangement, oaonium salt formation, ethers, acids, halides, etc. I n general the treatment differsfrom that developed previously by Sidgwick in emphasis and terminology more than in substance. Hahn has little or nothing t o say of dipole moments, polar molecules, or co*rdination, while he stresses kernel deformation and the donor-acceptor relationship. His exposition is a refined and extended electronic interpretation of the earlier ideas of F h r scheim. The author's explanation of the apparent tetravalence of boron in diborane involves the withdrawal of a K-shell electron into the L-shell. This occurrence seems improbable, however, because of the large amount of energy that would be required. E. A. WILDMAN B ~ a ~ C n om~ m o a RICBMONO,