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hook a r e the discussions of the author’s idras on the composition of tn-o or more simple systems t o form a complex system, the Pauli exclusion principle. a n d the s h a r p distinction b e t n e e n “internal” and “external” \ \ a v e functions These m u s t be studied t o understand the basis for the startling results n h i c h the authoi has predicted from his theory: the value of 1/137 for the fine structure constant, the mass ratio of thc proton a n d electron, ctc T h e sophisticated reader will undoubtedly find here man! things n i t h n h i c h he nil1 n a n t t o disagree. h u t the reviener believes t h a t if he approachrs the theory a t all sympathetically he vi11 also find much t h a t is stimulating and provocative of further thought. E 1, H I L L A p p l z e d C h e m i s t r y j o r Engineers By A F. I3 W ~ R D 19 Y 12 cm ; XI a n d 127 pp. London: Longmans, Green a n d Co , 1936 Price. 5s T h e writing of a n easily understandable book on applied chcmistry for engineers is n o r a s v task. T h e present hook is intended, the author tells us in his preface, t o provide a practical course in applied chemistry for s t u d e n t s of mechanical, municipal, or electrical engineering in technical colleges a n d universities. As a n alternative, i t s use is suggested t o s t u d e n t s of pure chemistry needing a n introduction t o applied chemistry. T h e book m a y appeal more t o the l a t t e r T h e method of instruction adopted is theoretical description follov ed b y experiment t o be performed; general references t o textbooks or pamphlets a r e added at the end of each p a r t . Almost half the volume is allotted t o water, domestic a n d industrial, i t s analysis and t r e a t m e n t . T h i s branch of the subject is dealt mith in detail; alternative a n d latest methods a r e given with, in some cases, literature references. T h e difficult problem of metal corrosion, including a consideration of overvoltage a n d the passive s t a t e , occupies the next thirty-odd pages, t h e elertrorhemical theory only of corrosion being considered. T h e rest of the t e x t of the volume is concerned n i t h coal a n d oil. I n contrast t o the section on iTater, the information is scanty, in the case of coal only proximate analysis being mentioned, and no calorific determination in the case either of coal or of oil. Some mistakes occur, for instance, a n obvious misprint in the equation on p. 56, t h e high value of the F a r a d a y (p. 73), a n d the description of methyl orange as a a e a k acid indicator (p. 116). H o n e v e r , the book as a whole serves a useful purpose. and a f u t u r e edition might be extended with advantage. W. H . PATTERSON.
Elektronentheorie der Metalle. By H . FROHLICH. 22 x 14 cm. ; vii a n d 386 pp. Berlin : Julius Springer, 1936. Price: 27 RM.; cloth-covered, 28.80 RAf. Dr. Frohlich gives a n exhaustive a n d detailed account of the modern electron theory of metals. T h e mathematical physicist nil1 find the hook full of useful information; in particular the chapters on the optical properties of metals are n o r t h mentioning. T h i s group of problems, t o which the author himself made valuable contributions, is particularly clearly exposed. T h e book appeals also t o experimentalists who want t o acquaint themselves n i t h the theory, a n d only the elements of wave mechanics are assumed t o be knoivn t o the reader. But Dr. Frohlich wmts the full a t t e n t i o n of his reader, a n d a superficial glance a t the book m a y n o t lead t o much benefit. T h i s holds particularly for a n English reader. n ho m a y he scared by the double difficulty of rather involved German constructions expressing involved arguments n ith m a n y afterthoughts H e will, hov ever, he rev arded for his patience b y much interesting information, a n d a very detailed list of references opens the w a y for further studies T h e book represents a fair s u m m a r y of the present position.
