RECENT R O O K S PUCTICALEMuLsIoNs. H. Bennett, Technical Director, Glyco Products Company. Chemical Publishing Company, Inc.. N e w York,.1943. x 462 pp. 9 figs. 15 X 22 cm. $5.00. In the preface the author states that although many books on colloid chemistry deal with emulsions in a theoretical and general manner, there is none which specifically discusses emulsions for the practical worker. Therefore this book attempts t o touch only lightly on the theory and concentrates on the art of making and applying emulsions. The author goes on t o state that the greatest drawback in the increased use of emulsions is the lack of proper understanding of the technique and formulation necessary to produce good emulsions. The main purpose 01 the hook therefore is to offer this practical information to the technical worker. The book is divided into two parts. The fist part, covering 200 pages, discusses the better-known emulsifying agents, types of emulsions, production methods, stability of emulsions, technical emulsions, and dispersing and wetting agents, I t concludes with lists of emulsifying agents, emulsions, and demulsifying agents. The second part offers a great number of formulas and practical hints for the production of emulsions to be used for specific purposes, as, for example, agricultural spray emulsions, cosmetic emulsions, food emulsions, leather treatment emulsions, polish emulsions, etc. If the baok, as indicated in the preface, is primarily devoted to the practical worker, the value of the 6rst part seems prohlematical because the author-pahaps unintentionally-relies t o a considerable extent on the reader's knowledge of the fundamentals of emulsification as well as a considerable knowledge of colloid chemical terminology. On the other hand, the reader who is familiar with the colloidal phenomena involved in the production, stability, and destruction of emulsions, will gather only a few crumbs of information which he does not yet possess. Since the book is devoted to the practical worker a mcre detailed and complete review of available emulsifying equipment i n d hints as t o its most successful operation would seem advisable. The very effective Tri-Homo Mill has heen overlooked completely. Reading of the first six chapters is extremely difficult and confusing because no general trend aids as a guide. Besides these shortcomings, some of the statements contained in the theoretical discussions are questionable. For example, the discussion of the appearance of emulsions under the microscope is misleading because the "soap pellicles surrounding the droplets" are not visible. The statement that interfacial tension plays a doubtful role in emulsion stability is not in agreement with experimental correlations. That the addition of electrolyte in small quantities increases the potential of the electric double layer a t the surface of the particle and thereby increases the viscosityoftheemulsionholdsonlyinafewspecificcases.Itistheprehistoryoftheemulsionas well as the type of electrolyte addedwhich will decideif the electrokinetic potential is further increased or immediately decreased. However, the thickness of the water layer will depend largely on the type of ions making up the electrical double layer. I t is inadvisable t o use the term osmosis in connection with the lowering of viscosity of colloidal solutions since no membranes are involved. In weaming of emulsions, the type of emulsifying agent or protective colloid used as well as the shape of the container are factors which may not be overlooked. I n discussing latex emulsions, carbon black and cement are listed as hydrophilic materials. They are not. Carbon black coagulates latex hy its power to adsorb considerable quantities of water when once wetted, whereas cement coagulates it as a result of released calcium ions. As long as we are dealing with a dispersion of water-in-rubber we are not dealing with an aqueous rubber dispersion, therefore the viscosity of the former is meaningless. A dispersing agent acts by increasing either the electrical repulsive charbetween primary particles forming a s aggregate, or by increasing their solvation. The cohesive attraction between particles forming an aggregate cannot be neutralized, being a constant depending on the mass of the particle (van der Wad's forces). In the literature references frequent use is made of a hook en-
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titled "Technical Aspects of Emulsions." This hook represents a compilation of papers read a t a symposium in London in 1934 and is edited by F. G. Donuan, not by H. Freundlich. The chapter on rubber latex to which frequent reference is made was cantributed by H. P. and W. H. Stevens. The list of dispersing and wetting agents (chapters VI and VII) would he of significant value to the reader only if the name of the manufacturer and, preferably, some of the specific applications were included, If the lis: of emulsifying agents and emulsions is considered in conjunction with the added literature' references, a valuable compilation of otherwise scatt*red literature has been made available. With Part I1of the baok the author has rendered a real service to all those who are interested in the production of a great variety of emulsions and who have not the time or training to enter this field from the ground floor. Not only does he offer a wealth of well-tested emulsion formulas, but he adds thereto from many years of personal experience the little practical "know-hows" which are so essential for satisfactory production. The second part of the hook is the one where the practical worker will be able t o gather valuable information, and it is this part which in combination with the literature references previously cited should make the book appeal also t o those who are looking for a condensed compilation of literature and patent references in the constantly growing field of technical emulsions. E. A. HAUSER
So You WANTTO BE A CHEMIST?Herbert Coith. McGrawHill Book Company, Inc.. New York, 1943. x 128 pp. 12.5 X 19 cm. $1.50. As a picture of what a professional career in chemistry involves, this is more general than the well-known "Chemist a t Work" and should occupy a place next t o the latter volume on the reference shelf of every vocational adviser, and indeed of every lihrary accessible to students of chemistry. However, it is profitable reading not only to the young aspirant to the chemical profession, but also t o those already engaged in its practice, who will get from i t a most comprehensive view of "the chemical industryu-its purposes, its organization, its general methods of work. The tangible elements of the chemical industry include raw materials, processes, and finished products. The attention given t o each of these involves establishment and control of standards; research; plant development; products service. The various relations of this classification are dealt with in illuminating detail. The language is simple, even colloquial, hut the author ohviously knows whereof he speaks. There is no nauseating and misleading emphasis upon "modern maNds." although many points in the discussion are illustrated by concrete examples from plant and laboratory. After the chapters which outline the chemical industry there are two valuahleones: "The Kind of Chemists Industry Wants," and "The Kind of Industries Chemists Want." Every prospective chemist could read these t o advantage. Answersgeuerally satisfying-are given t o most of the questions which hudding chemists raisshould r a i s e a n d one finds much sound advice on the training of chemists. Students are urged t o train themselves broadly and to take a broad view of their coming profession. "Chemistry need not be a chain holding a man in a laboratory where he works out answers for Torn, Dick, and Ham, on the outside t o take and make use of. Chemistry should he a tool which a man uses as a supplement t o other capabilities and which thus enables him t o meet Tom. Dick, and Harry, in any corner of industry or commerce,,and help all three of them to do a better job than they had been able to do before the tool of chemistry was brought t o their attention." NORRts W. RAnssTRAu BROWN UNIVBRSITY m O Y m B N C B , RAODH ISLAND
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