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Book Reviews Colloidal Hydrodynamics. The0 G. M. van de Ven. Academic Press: London, 1989; 582 pp. $77.50. This volume, on microhydrodynamics in colloidal dispersions, written by one of the leading contributors to the topic, is the latest in a series of monographs on colloid science (initiated by Academic Press under the managing editorships of Professors R. H. Ottewill and R. L. Rowell) and follows the tradition already established by the previous volumes in the series; i.e., each volume is an in-depth exposition focusing on a single topic of central importance to the physics and chemistry of colloids. The previous three volumes were concerned with dispersion forces (by J. Mahanty and B. W. Ninham), zeta potential (by R. J. Hunter), and polymeric stabilization (by N. H. Napper), and the present volume takes on a topic that is equally important in the study of stability, deposition and flow of dispersions, a topic which, nevertheless, has been left to specialists among specialists. The author, The0 van de Ven, along with his former mentor and colleague a t the Pulp and Paper Research Institute of Canada in Montreal, the late Professor Stanley Mason, has devoted many years of his career to the study of the microhydrodynamics of colloids (Le., hydrodynamics a t the level of the colloid particle) and the book reflects this experience and philosophical orientation. Although the book is not formally divided into various sections, the individual chapters [with the exception of the first (introductory) chapter on basic concepts dealing with colloidal forces and fluid dynamics] fall into four groups. The first of these concerns Brownian motion of noninteracting particles and the behavior of such particles when subjected to external fields (hydrodynamic, gravitational, electrical, or magnetic), and these are discussed in Chapters 2 and 3, which form almost half the book. These same topics for the case of interacting particles form the next group and are treated in the next two chapters. The content here is restricted to interactions between two particles at the most. Chapter 6 stands by itself and deals exclusively with particle-wall interactions (relevant in filtration, deposition, and coating phenomena). The last group, on multiparticle interactions, consists of the final two chapters (7 and 8) and deals with “concentrated” dispersions, Le., those for which one has to go beyond two-body interactions to describe the macroscopic behavior. A basic understanding of translational and rotational Brownian motion is of course indispensable for dealing with not only colloidal hydrodynamics but also stability of colloids in general. In contrast to most other currently available books on colloids, this volume presents a very good summary of this topic a t a level sufficient for studying most problems in colloids. In addition to the Langevin theory of Brownian motion, this chapter includes topics such as friction on charged spheres surrounded by ionic clouds and hydrodynamic approximations suitable for describing Brownian motion of particles with permeable (adsorbed) layers. These latter topics, although fairly standard now, are available mostly in journal articles currently, and it is good to see them organized in “neat” packages. This chapter, as most others, ends with a brief overview of some of the experimental techniques available, in this case for measuring the diffusion coefficients. This is followed by a rather extensive discussion of behavior of particles in external fields (in Chapter 3, the longest chapter in the book, spanning almost 200 pages). Here, the author discusses in considerable detail the hydrodynamics and electrohydrodynamics of flow around spheres in simple shear, flow around cylindrical, ellipsoidal, and spheroidal particles and deformable drops, and diffusion of particles of various shapes in external fields. Also included are discussions of diffusion in Poiseuille flow, viscosity of (noninteracting) dispersions, and rheooptics of dilute dispersions. This is followed by (relatively) brief treatments of colloids in gravitational, electrical, and magnetic fields and electro- and magnetorheology of dilute dispersions. The chapter concludes with an overview of experimental techniques 0743-7463191/ 2407-0434$02.50/0
such as rheometry, rheooptical measurements (light scattering, turbidity, birefringence, and dichroism), photon correlation spectroscopy, and electrophoresis. This section on experimental techniques also includes brief descriptions of a few experimental designs that have been used in the author’s laboratory for recording and analyzing particle motion in a variety of flow fields. Chapter 3 is the most detailed of all in the book, and in most cases the presentation includes all the relevant equations, boundary conditions, and solutions. In many instances, the author also points out what extensions are available in the literature and what additional work may be desirable. There is plenty of information in this chapter to keep any aspiring hydrodynamicist busy for a while. The next two chapters cover roughly the same general topics, but this time for a pair of interacting particles. The discussion here is of course much less extensive, largely due to the fact that these are still developing areas. Chapter 4 reviews the forces, torques, and mobility (and hydrodynamic resistance) tensors and matrices needed for describing the relative Brownian motion of pairs of spheres. This is followed by brief summaries of virial expansion for the mutual diffusion coefficient for hard spheres, pair distribution of “soft” spheres, and perikinetic coagulation. Chapter 5 then moves on to trajectory analyses of interacting pairs and stability of dispersions analyzed from this standpoint. Related topics such as orthokinetic and perikinetic coagulation under shear, PBclet-number expansions, viscosity of dispersions for hard spheres and soft spheres (i.e., the secondary electroviscous effect), and interaction under gravitational and electric fields then follow. The material in this chapter is restricted to two-particle interactions only. Chapter 6 is a departure from the previous ones, but is nevertheless equally important from the point of view of applications. The focus here is on particle-“wall” interactions (although, in this sense, it is a limiting case of some of the material treated in earlier chapters), which, on occasions, play a dominant role in deposition, coating, and filtration phenomena. Partly due to the geometries involved and partly because of the types of information sought, an Eulerian approach has been the most useful for this class of problems [in contrst to the Lagrangian (trajectory) approach used in the earlier chapter], and most of the discussion in this chapter focuses on this approach. Drawing largely from a review article published in Advances in Colloid and Interface Science by the author and some of his colleagues, this chapter deals with such topics as development of convective diffusion equations for deposition on substrates, correlating equations for mass transfer rates, and the role of boundary conditions (at the substrate) on the kinetics of deposition. The final two chapters provide a glimpse of an area that is still in its infancy, namely, the effects of multiparticle interactions (with an emphasis on problems related to the flow of dispersions). In this sense, these two chapters are the logical next step to the material in Chapter 5, which, as mentioned earlier, is restricted to two-particle interactions. Chapter 7 sets up some of the basic ideas or formalisms required for examining multiparticle interactions in a systematic manner. These include brief summaries of singularity methods for determining resistance tensors and particle velocities, pairwise additivity of forces and velocities, and convective diffusion equation for the pair-distribution function. Some discussion of viscosity of semidilute dispersions is also included here. Chapter 8 takes this material one step further and presents two examples of how the study of multiparticle effects may be approached. One is the effective-medium approach for the density-expansion of viscosity and the other is a more ambitious one in which the convective-diffusion-equation formalism for the pair-distribution function (introduced in Chapter 7 ) is used in combination with a suitable statistical mechanical approximation for the potential of mean force in concentrated systems. These last two chapters merely outline
0 1991 American Chemical Society
Book Reviews some plausible formalisms, since very few detailed results are available in the literature. Chapter 8 concludes the discussion of concentrated dispersions with a brief outline of diffraction and scattering techniques that are becoming popular (and very useful) in studying dense dispersions. The style of the presentation and the amount of details presented, particularly in the first six chapters, make this book quite suitable for use as a textbook in advanced courses, although the author has not included exercises or problems. [In fact, many of the details needed (or, already presented) in the development of the material in the book can be cast (or, recast) in terms of exercises and problems.] The book is also an excellent source of information for those entering or already active in the study of dynamics of colloids. Although the book is primarily theoretical in its orientation, almost all the topics covered and the results reported have their foundation in actual experimental observations; in turn, in many cases, the theoretical insights have led to special experimental designs. In view of this, and because of the wealth of information available here on the motion of single particles (of various shapes) and of interacting pairs, experimentalists in colloidal dynamics will also find this volume a very good addition to their library. The references, collected together at the end of the book, appear to be sufficiently comprehensive. [An error in the expansion for AZChE J. in the reference list deserves mention. AIChE stands for American Institute of Chemical Engineers, but it appears
Langmuir, Vol. 7, No. 2, 1991 435 consistently as Assoc. Ind. Chem. Eng. in the reference list. Readers unfamiliar with this journal may want to make a note of this to avoid wasting time hunting for a nonexistent journal. The reference list also has two incomplete references (Hannon et al. 1982 on p 574 and van Veluwen et al. 1987 on p 578).] A larger and more detailed subject index would have been preferable for a book of this scope and size, but the table of contents is more extensive than normal and makes up for some of the deficiencies in the index. Overall, this book is a very good and very welcome addition to the growing literature on colloids and provides a perspective that is both important and essential for developing fundamental theories of behavior and properties of colloids. Moreover, it collects together details that are scattered over a wide body of publications in colloids, fluid dynamics, and engineering. This is not a book on rheology of dispersions as rheology is commonly approached; rather, its goal is to set forth some of the building blocks necessary for developing a comprehesive approach to the rheology of dispersions, and it succeeds well in accomplishing this task. The price of the book ($77.50) is reasonable by today’s standards. Dr. van de Ven deserves praise for a valuable contribution to the literature, and this book deserves a place in the library of anyone interested in fundamental colloid science or low-Reynolds number hydrodynamics. R a j Rajagopalan, Department of Chemical Engineering, University of Houston
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Colloidal Dispersions. W. B. Russel, D. A. Saville, and W. R. Schowalter. Cambridge University Press: Cambridge, 1989.525 pages. Because of its broad interdisciplinary nature, “colloid science” will never see a definitive text. Most if not all previous books have emphasized concepts of applied and molecular chemistry associated with dispersed systems. The major contribution of Colloidal Dispersions is the priority and depth of coverage given to statistical physics and transport phenomena as these subjects relate to understanding colloidal systems a t the level of the microstructure of a dispersion. While written by engineers, this book is far from a conventional engineering text because it places more emphasis on basic principles than on applications. It fills a long-standing void by combining colloidal chemistry, statistical mechanics, and fluid dynamics to understand both static and dynamic properties of suspensions and is a most welcome addition to the literature. The homework problems included at the end of each chapter and the well-written text make the book an attractive candidate for an advanced (second level) course in colloid science. One of the finest chapters of the book is the first, which surveys interesting phenomena of colloidal systems and touches on some nice historical notes. With its photographs and excellent discussions, this chapter is certain to pique the interest of the reader. The next three chapters review fluid dynamics a t low Reynolds numbers, the statistics of Brownian motion, and classical electrostatics. T o get anything out of these chapters, the reader must have a solid background in mathematics, especially vector calculus. The assumed exposure to fluid dynamics is, in fact, a limiting factor in determining the appropriate audience for this book; second-year graduate students in chemical engineering and physics should fare well, but chemistry studies might have problems (at least in the United States). Basic forces between colloidal particles are treated in Chapters 4-6; the depth and cohesiveness of this treatment is a strength of the book. A brief but reasonably complete analysis of the Gouy-Chapman model of the electrical double layer precedes material on calculating the screeened electrostatic forces between two charged surfaces. I appreciate the authors’use of the Maxwell electrical stress tensor for these force calculations, which is a more sound formulation than the conventional approach based on osmotic pressure. The Derjaguin superposition approximation for curved surfaces is covered. Noncontinuum and specific-ion effects on the double layer (e.g., the Stern layer) are not covered. Chapter 5 provides an excellent overview of dispersion forces and their molecular origin, presented in a manner that assumes very little formal background in concepts of molecular polarizability and spectroscopy. A clear, mechanistic picture of the Hamaker constant is conveyed, thereby eliminating the perception of empiricism often associated with the way dispersion energies are incorporated into models for particle attraction. The discussion of interparticle forces continues in Chapter 6 with the role of polymers in either a dissolved or adsorbed state. The use of polymeric additives as stabilizing or flocculating agents continues to gain technological importance, so that the comprehensive treatment of this subject is warranted. Only one chapter (7) is devoted to electrokinetic effects, specifically electrophoresis, suspension conductance, and suspension dielectric dispersion. This limited coverage for an area of such traditional and practical importance seems too thin and
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overly brief, especially compared to the coverage of other topics in the book. The next two chapters deal with the stability and flocculation of suspensions stabilized by electrostatic forces and polymeric additives. As usual, the focus is on two-particle forces and dynamics. Both Brownian and shear modes of coagulation are included in the models for the time evolution of the two-particle probability function. The statistical approach used here, employing a momentum-free Fokker-Planck equation, is generally not found in other texts on colloid science, which instead rely on Smoluchowski’s original model. In Chapter 10 the authors present models for the pseudoequilibrium structure of suspensions based on statistical thermodynamic formulations in the context of the McMillan-Mayer theory of solutions, including distribution functions and pairwise additive potential energies between particles. Transport phenomena of suspensions are the focus of the final four chapters. The topics include particle capture during flow through porous media (related to deep-bed filtration), sedimentation, diffusion by Brownian motion, and rheology. The depth of coverage here is definitely superior to that given to these subjects in other texts on colloid science. In these chapters, the authors clearly demonstrate the interplay between macroscopic rates and evolution of the microstructure of a suspension, thereby tying this section to the previous chapters. This section of the book, along with Chapter 7 (electrokinetics), should appeal to those readers interested in the engineering consequences of colloid science. A major problem is that an ocean of material (about 360 pages) must be crossed to get here, so that some short cuts through the first two-thirds of the book are necessary in a onesemester course based on this text. Within the context of their objective, as stated in the preface “...to impart a quantitative understanding grounded in basic theory and coupled to experiments on well-characterized model systems”, the authors have succeeded in producing a first class text on the physics of colloidal dispersions. This success was achieved a t the expense of breadth, however. Subjects more aligned with applied chemistry, such as synthesis and growth of particles, wettability and dispersion, capillary forces, and methods of particle characterization, are not treated to any significant extent. Also missing is any discussion of molecular assemblies (micelles, microemulsions) even though the importance of this “classification” of colloid is acknowledged in the introductory chapter. Important omissions within the framework of colloidal dynamics include nonspherical particles (except for dumbbells) and fluid particles (droplets and aerosols), as well as boundary effects on particle mobility and transport. On balance, however, this is an excellent book that conveys the essential concepts and quantitative models for understanding colloidal systems a t a fundamental level. Colloidal Dispersions clearly sets a high standard for the teaching and understanding of colloid science in terms of relating microstructure to macroscopic behavior. There is no question that it is a necessary reference for anyone seriously interested in colloid science. I have chosen to require it as the text for the advanced course in “colloids” taught a t Carnegie Mellon, and I look forward to the learning experience through which both student and instructor will go. John L. Anderson, Department of Chemical Engineering, Carnegie Mellon University
0 1991 American Chemical Society
