Chemistry for sanitary engineers

BOOK REVIEWS CHEMISTRY FOR SANITARY ENGINEERS, by Clair N. Sawyer. 367 pages, diagrams, 6 X 9 in. New York, McGraw-Hill Book Co., hlc., 1960. Price, $9.50. Books on the subjects not already overwritten are always welcomed for filling the gap. Chemistryfor Sanitary Engineers fills a vital need but its acceptance will not be based on this alone. Dr. Sawyer, one of sanitary engineering's foremost scientists, has prepared a readable, concise text for the student and a handy reference for the professional engineer and plant operator. Except for advanced degree candidates, there is little opportunity for undergraduates in the field to obtain training in all the various chemical subjects so integral to sanitary engineering. This book serves to effect such coverage. It is divided into two parts: the first nilm chapters summarize the basic priuciples of such topics as biochemistry, radiochemistry and colloidal chemistry; the next 24 chapters are devoted to various sanitary chemical tests for water, industrial waste water, and sewage. The experienced sanitary chemist will find these sections to be complimentary to the A S T M Manual on Industrial Water and the Standard Methods. Actual analyrical procedures are not presented but the ilnportance of the test, the physical-chemlcal or biological principles behind the methods, and the applications are described. The clarity of the presentation on pH, acidity, and alkalinity merits review of these flmdamental but frequently misunderstood relationships by the experienced engineer as well as the student. The description of the role of nitrogen is another example of well developed but easyto-follow presentation. There are relatively few references. Future editions might be enhanced by addition of upto-date bibliographies for use by the advanced student or practicing engineer, lustrumental chemical analytical procedures such as those employing visual and infrared spectrographic and chromatographic methods might also be included. Their applications, especially in

research work, are becoming more important in the field. In this reviewer's opinion, Chemistry for Sanitary Engineers will be a worthwhile addition to the library of those in the fields of water or waste treatment, water-slde corrosion or sewage treatment. ROBERT A. BAKER The Franklin Institute Laboratories DIGITAL AND SAMPLED-DATA CONTROL SYSTEMS, by Julius T. Tou. 631 pages, diagrams, 6 X 9 in. New York, McGraw-Hill Book Co., Inc., 1959. Price, $15.00. This excellent book is an important accession to the few books on sampled-data control systems recently published. It will be useful both as a text book and as a reference. Most of the chapters begiu with an iutroduction, giving the reader some idea of what to expect. A conclusion at the end of many chapters emphasizes the main points preanted. The chapter arrangement is extremely logical, and the material within the chapters shows much more than just casual organization. The writing is clear and concise and sufficient tables and diagrams are included to enhance presentation greatly. The first two chapters are of introductory nature. The use of root locus for design of continuous systems has been skillfully expounded. The next four chapters deal with system analysis. The theory and application of both Z and modified Z transform methods are given thorough treatment. System design, error analysis, statistical method, and finite sampiing are covered in the remaining three chapters. Multirate sampled systems are discussed. One chapter is devoted to the description of the analog-digital conversion principle. Nyquist and Bode plots as well as root locus method in sampled-data systems have also been appropriately presented. Many problems given in the appendix are extremely helpful to all students. A ready 55