gI:~sscs, and other sperial solid-state systems as samples; gxscs and gas-disp m o i d s a s samples; poI~rizat,ionand spertrol~oli~riaation techniques; r and m v i h e s ; quenching; comparative spcrtromptry: sorptives and molecular films; and, advanced instruments like the highly prol,able forthcoming interference spertrofloorometcr. JACK DE MENT
De Ment Lahoralories Portland, Oregon Direct Melhodr in Crystallography
nr. nr.
Ilrooljson. Oxford, At the Clarendon Press, I9G1. viii 14-1 pp. Figs. and tnbles. 14.5 X 22 em. $4.80.
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T h r term "direct methods" means, in t h e dmvt. eontcxt, met,hods for deriving t h e p h i ~ + eof~ ohserved stmctorr nmplitudcs by purrlg !mathemstid means nnd thus going " d i r ~ c t l j " from the ohs~rvecl ditlrnrtion data from a crystal t o thp calculation of t h r electron density in t h r unit. e d . Thew t ~ c h n i q u r sar? usnally formulnted in trmm of n set of mat.hematicnl steps which HPP t o hc carri~dout in a rout,irw ~ s yand , w r y often ~ w p i r ethe use of an elcrtlxmic computer. Their advantage is t h a t t,hey are almost completely objcetivr, and their grcxtrst disadvantage is t,hat they are almost e o m p l ~ t r l y01,jrctive. This monograph recounts the history of direct methods beginning v i t h thrir inception in 1!l48, and following t,llrongh t h e many suhsrquent suggcstions down t o t h e pres~nt,.A very uscful fenture is the illus tration of some of tho "&hods hy t h e prcsentat,ion of simple examples whirh t h e reader may t r y for himself (the solutions are e v ~ n at t h e end of the lrook). The style of t,hr author is admirahlv clcar, and he has tnkcn t h ? trouble t o rework maqv of thc soggrstrcl nlethods in order that thepresentation may Re as lucid as possible. Thp author points out t h a t the record of the st,ruetures which have thus far been solved by direct mcthads is, st the prcsrnt timnc, rstrnsivr hut not impressivr. I n other words, t h e standard mcthods for stn~et,urpdetermination arc hy no means ahsol&. On t h e other hand, he feels t h a t in mother decade direct methorls will be of major importance. This means t h a t the determination of structures will be relegated t o technicians. The r e v i ~ m awaits r this prcsurnetl drvelopment n-ith great interest. Finally, the author of this charmingly writtm littlr hook warns the prospect.ive rexdrr in the preface with t h e follorl-ing statement: "For the stranger or t h e compnrativr newcnmcr t o t h e field of crystallography this monograph is not recommmdcd; indeed a more unsuitable avenue of approach could hardly he imagined." This r r v i ~ w wis in complete agreement with t h e above statement. This monograph can he recommended, howcver, t o experts in t,he field, and t o those whose knowledge of structure determinations is somewhat more t h a n casual. It should he required rending in any graduate course in X-ray erystnllography. JERRY DONOHUE Universilz, of Southern Cal
