N E W BOOKS accumulated in the last two decades. This fact alone would be a sufficient justification for its acquisition. The chapters on analysis of failures and on methods of evaluating susceptibility to stress-corrosion cracking will prove to be, no doubt, of great value to engineers and scientists confronted with service failures. In fact, much of the book appears to have been written with this particular point in mind. The author has followed the sound practice of inserting a section on the mitigation of stress-corrosion in each of the nine chapters dealing with the main alloy groups. Equally commendable are the summaries of the main points at the end of each chapter and the extensive lists of references. However, the claim that the work reflects also the current mechanistic thinking cannot be validated. The implied suggestion (p. 37) that stresscorrosion phenomena can be explained in terms of a single universally applicable, electrochemical-mechanical mechanism has been the subject of severe controversy over several years. The main criticism of the book must be, therefore, that the existence of this controversy is not made apparent. In fact, some of the currently popular mechanical theories of failure-e.g., tarnishrupture-are not discussed, and it is perplexing to find that evidence originally presented by the proponents of the tarnish-rupture mechanism in support of their theory is presented in the book as evidence for the electrochemical-mechanical theory without any elaboration. Nevertheless, despite the shortcomings of the sections dealing with the mechanisms, anyone interested in the subject of stress corrosion should have access to this book. The literature dealing with this subject is so extensively scattered among numerous technical periodicals and texts of conference proceedings, that an attempt, such as this, to bring together and systematize information, must be welcomed. A. John Sedriks
Mathematical Modeling in Chemical Engineering. R. G. E. Franks. i x f 285pages. John Wiley & Sons, Inc., 605 Third Ave., New York, N . Y . 70076. 7966. 370.95.
It is the author’s contention that mathematical modeling can be the framework of an economical, quantitative, and orderly approach to technical problems. The leitmotiv in his exposition is analysis, or at least an analytical approach which, in the past, has been frustrated by a computational bottleneck. The author believes that the computer has largely removed that bottleneck, leaving the analytical approach unfettered. Where computers are available, his contention is probably true. However, some time will be required to develop analytical habits in the professional mass. The most striking thing about the book is the familiarity of the example material. T o a reader used to being bowled over with mathematical symbology, it is refreshing to encounter a friendly heat exchanger or distillation column. This is primarily due to the author’s belief that mathematical intricacies of simulation can usually be handled by someone other than the engineer with the original problem. If we assume this belief to be correct, then the book may well be unique as a text that can be assimilated by undergraduates with limited mathematical backgrounds, and by practitioners whose math has grown rusty with disuse. After reading through the book, I still have the nagging suspicion that computers are not as readily available as the author supposes. If so, the book will not find wide use. Where the computers are available, however, it constitutes an admirable text, especially for in-plant courses, the origin from which it grew. Mr. Franks is to be congratulated for providing a text which is really quite formidable but which doesn’t appear so because of the lack of mathematical impediments. Joseph Haggin
LETTERS Sir : I read
the article “Planning Experiments to Increase Industrial Research Efficiency” by W. G. Hunter and M. E. Hoff (I&EC, March 1967) with great interest. The Customer Service Laboratory, Continental Oil Co. (Petrochemical Department), Teterboro, N. J., has been statistically designing experiments for the past 5 years. Our aim is not better planning or more efficient operation of research programs but providing our Marketing Department with new products as sales tools. Our laboratory has developed, with the help of statistically designed experiments, a procedure which helps vinyl processors to cut compound-development time and reduce costs without sacrificing quality. One element of this procedure is now well known as the Conoco Blend Master Chart. In my opinion, the statistical approach used a t the Customer Service Laboratory and the work of Dr. Hunter and Miss Hoff are steps in the direction of taking polymer or plastics technology out of the realm of black magic and into the field of science where it belongs. John W. McBroom Customer Service Laboratory Continental Oil Co. Corrections Through a publisher’s error, the following information was left off Figure 7 appearing in Vol. 59 (4), 46 (1967): Curve 1. C/d = 0.020; h / d = 0.5 Curve 2. C / d = 0.025; h / d a 0.75 Curve 3. C / d = 0.025; h/d = 1.0 Curve 4. Single-flighted auger in draft tube, C / d = 0.075; h / d = 1.15 Curve 5. C / d = 1.08; h/d = 0.60 I n the abstract of the paper by Chueh and Prausnitz [I&EC 59 (5), 14 (1967)], the third sentence of the second paragraph should read: “The standard-state fugacity for a subcritical component is the fugacity of the pure liquid at a fixed pressure and a t system temperature while the standard-state fugacity of a supercritical component is given b y Henry’s constant of that component a t a fixed pressure, at system temperature and at fixed solvent composition.”
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