- Email: [email protected]
Colloid electro-optics — theory, techniques, applications
139
inclusion of more plant and process engineering data in these sections to complement the theoretical analyses and modelling which are well covered. Published engineering data is available, albeit not so widely as is the more scientific data. But this is surely a good reason for their inclusion in a book describing advances in an engineering subject -even if it were done at the expense of omitting some of the mathematical developments (many of which have appeared in book form previously) for to an engineer the real test of theories and models is their ability to be used reliably in the design process. The author himself has noted that “inany important problems which require discussion are not included”, perhaps design engineering and operational experiences are two of these. Professor R.J. Wakeman University of Exeter
Colloid electro-optics - theory, techniques, applications, by S.P. Stoylov, Academic Press, 1991, pp. 280, price E35.00, ISBN O-12-672965-4. “Doyou feel the air for electric influences Like some strange magnetic apparatus?... And from all this, do you make ca~u~ations?” (D.H. Lawrence in ‘Bare Almond Tree’) For those of us who work in the field of electro-optics this book is most welcome. It is an attempt to provide the basis upon which a full understanding of the application of electro-optic methodology to the study of particle colloid suspensions can be established. Briefly stated, electro-optics is the study of the optical properties of media, in this case colloidal suspensions, when they are subjected to electric force fields. For molecular solutions or particle suspensions, the resulting accompanying optical changes are the result of the collective ~lloidal electrical pro~~ies coupling with the applied field so as to cause orientational order on the overall medium. For non-spherical particles which exhibit geometrical anisotropy the rotational alignment can be moni~red by observing changes in one or other of the optical properties. The earliest phenomenon observed was that of electric birefringence or the ‘Kerr Effect’. Since that time electric dichroism, electric field light scattering, electroflorescence, eleotro-optical rotation and electrically induced Raman scattering have all been observed as have been the related phenomena of dielectric and conductivity changes.
140
Based primarily upon the author’s research interests, this book features the theoreti~l expressions for both electric field light scattering and electric birefringence. The book is at its best in two outstanding features. The first is as a most comprehensive review to date of the theory for particle orientation in electric fields and the observation of this via birefringence and scattering when both continuous and pulsed electricfields are used. The theory is complete in its analysis of both small and large particles in suspension with respect to the wavelength of light. ~athemati~l treatments of the induced effects, both for their magnitude and their time dependence are comprehensive. In this area the work is nothing less than a handbook for those of us who have a practical interest in electro-optic methodolo~. The second endearing feature is the presentation of the extensive tabulated data for the colloidal systems studied to date. Tables are given for a range of oxides, clays, aerosols, dyes and in the related biological area for viruses, cells, organelles, membranes, nucleic acids and proteins. Whilst going beyond the stated title with these last examples, the compendium of data nonetheless is really useful. In addition the book contains an admirable and perhaps the most comprehensive attempt to date, to classify the observable electrical characteristics of colloids and to give an insight into their origins. The text is far more comprehensive than standard textbook descriptions of permanent and induced dipoles. Theoretical expressions are given which attempt to account for surface induced polarisation effects, surface induced dipole moments, the influence of inter-particle attractions on dipolar properties, the ~nt~bution from surface charge and electrophoresis and their observation. All of these are translated in terms of observable electric birefringence and light scattering data. The important concept of the role of electrical properties on suspension stability is also given a chapter to itself where the use of electro-optical methods for the study of this topic is discussed. The aims of the work are admirable. If there are shortcomings, and sho~#rn~gs there must be, then in the opinion of this reviewer they are twofold. The first is that over the thirty years of electro-optic research, not only has the theory and the range of materials studied expanded drastically but so has the number of electro-optical phenomena studied and the sophistication of the related equipment been developed extensively in certain laboratories. This has little exposure in the text and the “graduate student” whom the preface says could benefit from the text might well be forgiven for thinking that electro-optic methodology is unjustly dated. Novel automated instruments exist which make the
141
subject more exciting than the impression given. The other limitation is that whereas mention is made of various electro~pti~ experiments which through their ingenuity have contributed to the wider understanding of colloid science, these have sometimes been given only cursory treatment in relation to work which emanated from the author’s own laboratory. This last is a small criticism however for a work which is outstanding in its general attribute of trying to draw the attention of the wider colloidal audience to a range of experimental methods that have a significant role to play in colloid science. For all those interested in the electrical properties of colloids, the understanding of colloidal stability and novel methods for measu~ng the relevant parameters, this book is of value. B.R. Jennings Research & Development Director ECC ln~~ation~ Ltd.
inclusion of more plant and process engineering data in these sections to complement the theoretical analyses and modelling which are well covered. Published engineering data is available, albeit not so widely as is the more scientific data. But this is surely a good reason for their inclusion in a book describing advances in an engineering subject -even if it were done at the expense of omitting some of the mathematical developments (many of which have appeared in book form previously) for to an engineer the real test of theories and models is their ability to be used reliably in the design process. The author himself has noted that “inany important problems which require discussion are not included”, perhaps design engineering and operational experiences are two of these. Professor R.J. Wakeman University of Exeter
Colloid electro-optics - theory, techniques, applications, by S.P. Stoylov, Academic Press, 1991, pp. 280, price E35.00, ISBN O-12-672965-4. “Doyou feel the air for electric influences Like some strange magnetic apparatus?... And from all this, do you make ca~u~ations?” (D.H. Lawrence in ‘Bare Almond Tree’) For those of us who work in the field of electro-optics this book is most welcome. It is an attempt to provide the basis upon which a full understanding of the application of electro-optic methodology to the study of particle colloid suspensions can be established. Briefly stated, electro-optics is the study of the optical properties of media, in this case colloidal suspensions, when they are subjected to electric force fields. For molecular solutions or particle suspensions, the resulting accompanying optical changes are the result of the collective ~lloidal electrical pro~~ies coupling with the applied field so as to cause orientational order on the overall medium. For non-spherical particles which exhibit geometrical anisotropy the rotational alignment can be moni~red by observing changes in one or other of the optical properties. The earliest phenomenon observed was that of electric birefringence or the ‘Kerr Effect’. Since that time electric dichroism, electric field light scattering, electroflorescence, eleotro-optical rotation and electrically induced Raman scattering have all been observed as have been the related phenomena of dielectric and conductivity changes.
140
Based primarily upon the author’s research interests, this book features the theoreti~l expressions for both electric field light scattering and electric birefringence. The book is at its best in two outstanding features. The first is as a most comprehensive review to date of the theory for particle orientation in electric fields and the observation of this via birefringence and scattering when both continuous and pulsed electricfields are used. The theory is complete in its analysis of both small and large particles in suspension with respect to the wavelength of light. ~athemati~l treatments of the induced effects, both for their magnitude and their time dependence are comprehensive. In this area the work is nothing less than a handbook for those of us who have a practical interest in electro-optic methodolo~. The second endearing feature is the presentation of the extensive tabulated data for the colloidal systems studied to date. Tables are given for a range of oxides, clays, aerosols, dyes and in the related biological area for viruses, cells, organelles, membranes, nucleic acids and proteins. Whilst going beyond the stated title with these last examples, the compendium of data nonetheless is really useful. In addition the book contains an admirable and perhaps the most comprehensive attempt to date, to classify the observable electrical characteristics of colloids and to give an insight into their origins. The text is far more comprehensive than standard textbook descriptions of permanent and induced dipoles. Theoretical expressions are given which attempt to account for surface induced polarisation effects, surface induced dipole moments, the influence of inter-particle attractions on dipolar properties, the ~nt~bution from surface charge and electrophoresis and their observation. All of these are translated in terms of observable electric birefringence and light scattering data. The important concept of the role of electrical properties on suspension stability is also given a chapter to itself where the use of electro-optical methods for the study of this topic is discussed. The aims of the work are admirable. If there are shortcomings, and sho~#rn~gs there must be, then in the opinion of this reviewer they are twofold. The first is that over the thirty years of electro-optic research, not only has the theory and the range of materials studied expanded drastically but so has the number of electro-optical phenomena studied and the sophistication of the related equipment been developed extensively in certain laboratories. This has little exposure in the text and the “graduate student” whom the preface says could benefit from the text might well be forgiven for thinking that electro-optic methodology is unjustly dated. Novel automated instruments exist which make the
141
subject more exciting than the impression given. The other limitation is that whereas mention is made of various electro~pti~ experiments which through their ingenuity have contributed to the wider understanding of colloid science, these have sometimes been given only cursory treatment in relation to work which emanated from the author’s own laboratory. This last is a small criticism however for a work which is outstanding in its general attribute of trying to draw the attention of the wider colloidal audience to a range of experimental methods that have a significant role to play in colloid science. For all those interested in the electrical properties of colloids, the understanding of colloidal stability and novel methods for measu~ng the relevant parameters, this book is of value. B.R. Jennings Research & Development Director ECC ln~~ation~ Ltd.