BOOK REVIEWS which are used as drugs such as cammercial methods of preparation, physical and chemical properties, standards and tests for id en tit,,^ and purity, as well as a d~scussionof their use and dose in medieinc. The text is necessary in the pharmacy curriculum and serves well as a reference book in chemical laboratories.
than many of the annual reports issuing from various offices in Washington. Xewcomers to the field of water desalting, and any others who want an over.%ll view of the present state of this rapidly expanding field, will welcome this review. There is a detailed discussion of various distillation processes carried out a t a fnirlv elementarv level with lucid dia-
unit area of evaporator pan for every 3 N. M. FERQUSONunits of irrigated land m a . Electrodialysis equipment is compared University of Houston in terms of a power index: Houston, Toxaa Electric power per unit of fresh water produced Prodv~tionrzte per unit area of membrane
Salt Water Purification
K.S.Spiegler, Technion-Israel Institute of Technology, Hitifa, Israel. John Wiley and Sons, Ine., New York, 1962. 167 pp. Figs. and tables. 15.5 X ix 23.5 cm. $7.50.
in terms of power consumption when eompared to the large scale plants. We learn also that 8uch cells should be operated a t an optimum current density, i:
I n these days of government-sponsored programs in fields such as the improvement of saline water we have come to accept the idea of research by committee. Certainly i t is hecoming mare and more conlmon to have books written by committees, and the rerult in some c a m is what one reviewer has called the %on-book." I t is refreshing occasionally, thenfore, to come across a book surh as this informative Mtle volume written by one man, which tells us more about salt water purification
The term a is proportional to the cost of power, whereas b is proportional to the cost of plant. I t is in giving such details as this that the book is most valuable. The minimum energy requirements for sea water purification are discussed in a simple manner also. Imagine an apparatus consisting of two reservoirs, one containing salt water, the other fresh
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water, both partly filled xith liquid and evacuated. The two containers are eonneeted a t the top through s. compressor. Since the vapor pressure of fresh u-ater is higher than that of salt water, the fresh water would eventually dist,ill over into the salt water container. However, if we use the pump r e could push the water vapor the other way from the salt water container into the fresh r a t e r container. The work done by a hypothetical pump of this kind working against a vapor pressure difference of 1.84% between sea water and fresh water (equilibrium vapor pressure of pure water is 0.0312 atm. a t 25'C) is 0.0312 atm. X 1.84 X 43.4 liters per gram of water w p o r = 0.0240 liter atm. per gram of water = 0.70 kwhr./m3 = 2.65 kwhr/1000 gal. The chapt,er an scale is a useful one also, particularly to tear,hers of freshman chemistry courses who might want to bring up to date their diseussion of hardness in water. Chemistry teachers will find the whole hook useful as x source of interesting examples of modern applied chemistry. Dr. Spiegler brings us back to reality in his summary when he states that unless sensational breakthroughs are made in water desalting, it mill be more economicel to transport agricultural products to arid regions than to grow then, there by irrigation with converted sea water.
J. 4 . SCHCFLE New Mezzco Insltlule of dirnzng and Technology Soeorro
