In these two volumes I have tried to outline our present knowledge concerning the chemistry of melts in metallurgy. Had I done this twenty years ago, it might have been possible to include almost all the chemical knowledge then available. But today, thanks to the difficult work done by many metallurgists and chemists, that is no longer the case. I have therefore been forced to make a selection and have chosen to describe and discuss systems which either exemplify important principles or are of industrial importance.
My survey deals first with Structure and Kinetic Properties, then with Thermodynamics and finally with Reaction Kinetics. In the first two parts I have dealt with metals, salts and slags, and with equilibria involving them. In the third part I have described reactions between metals and gases and metals and slags, and those interfacial phenomena which affect all reactions proceeding across interfaces. The rates of many metallurgical reactions are controlled by the kinetics of mass transfer as distinct from chemical and electrode kinetics. I have therefore dealt with both chemical kinetics and mass transfer in the sections leading up to gas-metal and slag-metal reactions. Because of the growing importance of dispersed phases, such as bubbles, foams and sprays, which are used to obtain high rates of processing per unit volume of reactor, I have paid particular attention to mass transfer involving drops and bubbles in reactions between metals and gases and metals and slags.
In many cases our knowledge of high temperature systems is greater than our understanding. Believing that it is most valuable to know the patterns of thermodynamic properties and kinetic behaviour, I have included tables and diagrams which illustrate these even when theory is lacking, and the data cannot be linked satisfactorily together.
I have tried to make this book understandable to final-year metallurgists and chemists and to graduates in industry and university. The training which metallurgists receive differs widely from one university to another in regard to its chemical and process engineering content. Some may therefore regret that more basic thermodynamics and kinetics have not been included, whilst others may be surprised to find some rather elementary matters set out in detail. I have tended to omit elementary information which is readily available in first and second year text books, but have included other elementary material-as for example on electrode kinetics and interfaces which has to be sought in books not normally used by metallurgists.
I may be criticized for not converting all quantities to S.I. units. I have not done this because virtually all the thermodynamic and structural data available today have been tabulated or plotted in traditional units. Thus the data which I have used and quoted in traditional units may be very easily combined or compared with other published material. Conversion to other units can be made when desired by means of the factors listed in my introductory pages.
Having worked in the field of chemical metallurgy for the past twenty-five years, I have seen the subject develop enormously, thanks to the distinguished men whose mimes occur many times in this book. Working with high temperature melts is difficult and often discouraging and making even simple measurements with accuracy, is far harder than with aqueous and organic solutions. I would therefore particularly like to acknowledge the inspiration I personally have drawn over the years from the work of Herman Schenck, John Chipman, Lawrence Darken, Otto Kubaschewski, John Lumsden and Kenneth Kelley. All of them by their researches or their writings, or both, have exerted profound effects on chemical metallurgy.
I also wish to acknowledge my indebtedness to the many able research students who have worked with me and who today are creating new knowledge in this important field. In doing so I must stress that their work with me has only been possible because of the generous financial help which I have received over the years from the Nuffield Foundation and from those helpful companies in the metal industries who have supported the Nuffield Research Group and the John Percy Research Group at Imperial College.