CHEMICAL & ENGINEERING
NEWS VOLUME se, NUMBER 39
The Chemical World This Week
FILM SPREADS. A film of hexadecanol spreads on the Urnberumberka reservoir in Australia, reducing amount of water lost by evaporation. Entire water surface of this reservoir, only
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part of which is shown, can be treated in about 45 minutes in a slow motorboat making seven or eight crossings of the lake. Daily "repair" runs take only 15 to 20 minutes
Monomolecular Films Aid Water Conservation Straight-chain alcohols form "liquid condensed" films on surfaces of reservoirs to cut down evaporation Development of a practical method to reduce evaporation losses from reservoirs and other open water-storage areas is shifting into high gear, with Australia and the U.S. leading the way. The brightest possibilities seem to be those in which pure, solid, longchain fatty alcohols—especially cetyl (hexadecanol) and stearyl alcohols ( octadecanol ) —are spread over water surfaces to form monolayers relatively impervious to water vapor. Evaporation losses from this country's lakes and streams exceed today's total use of water by all the cities and towns in the nation. So said U.S.
Senator James E. Murray in an address at the ACS meeting in New York. His address was read before the Symposium on Transport Processes Through Monolayers, held jointly by the Division of Colloid Chemistry and the Division of Water and Waste Chemistry, by Eugene D. Eaton, consultant to the Senate Committee on Interior and Insular Affairs. "The United States is entering a period of enormous growth," the Senator forecasts, which will more than double our need for water. By 1980, he expects a continental population of at least 250 million, compared with
about 180 million now, with industrial production tripled, and the gross national product in excess of $1 trillion per year. This means, he declares, our need for "good water" will climb from the present level of 250 billion gallons a day to some 600 billion gallons. To satisfy this need, the U.S. will have to boost reservoir capacity from 275 million acre-feet to 600 million or more, the Senator says. He figures this increase would include at least 14 million acre-feet of additional capacity on the Colorado River (to conserve flood Rows now only partially used) and anSEPT.
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POWDER EQUIPMENT. Dr. Robert G. Vines of Australia's Commonwealth Scientific and Industrial Research Organisation feeds block of hexadecanol into a motor-driven grinder which blows out powdered material. Fine particles settle on water surface, spread quickly to form monolayer
other 30 million acre-feet of storage on the upper Missouri River. Evaporation from existing reservoirs on each of these two river systems already exceeds a million acre-feet a year, he estimates. Australians Pioneered. Many foreign countries, too, face the same type of problem. About eight years ago Australia launched a concerted practical effort to solve this growing world-wide dilemma. Four or five years ago the U.S. Department of Interior began a similar but much larger program. Now, work is being carried on also in such arid areas as Israel and East Africa. Finding cetyl alcohol best for its work, the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO) developed a process for spreading the waxy material cheaply and easily over lakes and reservoirs. Dr. Robert G. Vines told the symposium of a mechanical grinder— essentially a fast-spinning wire brush— his group developed. Installed aboard a small motor boat, it reduces solid chunks of the alcohol to a fine dust and blows the dry powder out over the water surface. The small particles (0.01 to 0.001 inch in diameter) spread spontaneously to give a monomolecular film. Highly efficient in calm weather, the monolayers cut evaporation losses by as much as half, says Dr. Vines. It doesn't work as well in high winds because the alcohol layer is then broken up and blown downwind across the surface. This leaves large expanses of uncoated water. The film 24
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re-forms readily when the wind dies down, he finds. Much of the Australian work on control of evaporation has been directed toward acquiring knowledge about rates and mechanisms of spreading and applying this knowledge in the field, William W. Mansfield told the symposium. He says that the CSIRO method can economically reduce evaporation losses by about 30% on the average for large or small reservoirs.
Dry Powder Thought Best.
Mr.
Mansfield, who pioneered this work, prefers to use pure, dry, powdered cetyl alcohol or mixtures of cetyl and stearyl alcohols. The tiny particles spread rapidly and form a monomolecular layer on the surface. Dissolving the alcohol in a solvent generally reduces its ability to cut down evaporation, perhaps because the solvent leaves "holes" when it evaporates from the film. He does admit that cetyl alcohol dissolved in petroleum ether seems to give an even better film than does the powder itself. But he sticks to the dry-powder technique, however, because he feels that solutions are not as practicable for large bodies of water. So far as other techniques are concerned, molten octadecanol is inconvenient and hard to handle, he points out. It requires heated, insulated spray equipment, which adds weight and bulk to the system. He doesn't favor emulsions or dispersions for large-area use because surface-active agents are needed to stabilize them. And these, he emphasizes,
drastically deteriorate surface-spreading properties of the suspended particles. Other workers, though, have successfully used dispersions, mostly on smaller bodies of water. W. J. Roberts of Illinois' State Water Survey Division, for one, has over the past four years cut evaporation by as much as 437c in small, shallow artificial ponds, during dry summer conditions, by applying hexadecanol in slurry form. During one relatively wet summer, the saving averaged only 22%. He did note biological attack on the film, but countered it with such algaecides as copper citrate. And Russell G. Dressier, a San Antonio, Tex., consultant, told of his patented "suspension process" which he uses to apply a commercial grade of stearyl alcohol (containing some cetyl). He pumps an aqueous slurry through plastic piping along the shore of a lake or reservoir (C&EN, June 30, 1958, page 4 4 ) . Automatic pumps continuously meter 1 ounce per hour of active material through each of a series of orifices spaced 50 feet apart. Dressier relies on prevailing winds to spread the film from his stationary sources. Film Must Re-form. A basic major difficulty in practical use of the film method for reducing water evaporation involves the monolayer's ability to re-form after it's disrupted by wind, rain, actinic radiation, or other cause. Cetyl alcohol seems to be the best self-healer of the materials field-tested. But even in this case it is generally acknowledged that some "repair work" should be carried out every day by applying additional amounts of the powdered alcohol to uncovered water areas. Somewhat unexpectedly, winds and biological attrition both seem to present considerably greater problems to U.S. field-testing than they do to that of Australia. Winds of less than 5 miles per hour give best results with hexadecanol films. At 5 to 15 miles per hour, efficiency is moderate; above 15 miles per hour, advantages are lost. Breezes above 5 miles per hour are more common in this country than in the regions of Australia where CSIRO's field-testing takes place. And film-decomposing bacteria (chiefly Pseudomonas) are more prevalent here, too. Food for Bacteria. According to Dr. Shih L. Chang of U.S. Public
Health Service's Robert A. Taft Sanitary Engineering Center in Cincinnati Ohio, Pseudomonas and Flavobacterium species can grow on hexadecanol, using it as their only carbon source. In a large-scale study, he recounted, 10% average surface coverage on Oklahoma City's Lake Hefner gave evaporation savings of at least 9%. But concentrations of bacteria normally present in the lake increased "markedly," though still remaining below PHS limits. Both these bacteria seem to grow faster on a hexadecanol film than on an octadecanol film, says Dr. Chang. In the laboratory, films on pure distilled water retain their ability to suppress evaporation for three or four days. But he finds that by the seventh day film effectiveness is completely by the fifth day, the film is useless. When these bacterial species are added to the water before a film is laid down, the H E W researcher notes a reduction in film efficiency after one day; by the fifth day, the film is entirely useless. Pure Materials Vital. Columbia University professor Victor K. LaMer, who organized the symposium, stresses the need for higher purity in commercially produced alcohols. Presence of lower-chain or branched-chain alcohols is deleterious, he states. And although stearyl alcohol films do not reform very well after being disrupted, he finds that mixtures of this and cetyl alcohol work much better in the laboratory in reducing evaporation from clean water surfaces than does hexadecanol alone. And they re-form nearly as easily as straight cetyl alcohol. Surface pressures up to 30 to 40 dynes per centimeter give effective "liquid condensed" films. This range of pressures can result from light winds under field conditions, he points out. Temperature of a liquid surface varies inversely with rate of evaporation. Dr. N. Lynn Jar vis and coworkers Carter O. Timmons and Dr. William A. Zisman at Naval Research Laboratory use thermistor elements to evaluate film-forming compounds. They find that a film of an n-alkyl alcohol such as hexadecanol reduces temperature drop by as much as 6° C. at the surface, under the influence of a stream of dry nitrogen. This NRL work confirms that changes in configuration—unsaturation or halogen substitution, for example—make fattyacid compounds less effective in retarding water evaporation.
Honored at ACS Meeting In New York City The ACS meeting in New York was a time for honoring chemists' accomplishments. Among such events, the Divisions of Colloid Chemistry and Physical Chemistry sponsored a Symposium in Commemoration of David C. Grahame; the Division of Medicinal Chemistry held a Frederick F. Blicke Symposium; the Division of Physical Chemistry sponsored a symposium on theoretical chemistry influenced by the late John G. Kirkwood of Yale. Another award at the meeting was the Hudson Award of the Division of Carbohydrate Chemistry.
TRIBUTE TO GRAHAME. Following a symposium commemorating the late Dr. David C. Grahame, Colloid Division's retiring chairman Dr. Stephen Brunauer (right) introduces Mrs. Grahame
HONORS TO BLICKE AND WHISTLER. University of Michigan professor Frederick F. Blicke (above, right) receives a bound volume of symposium manuscripts from Dr. George Webster of the University of Illinois following the symposium in his honor. Dr. Roy L. Whistler (below, right), Purdue University, receives the 14th Claude S. Hudson Award from Dr. John L. Hickson, chairman of the Carbohydrate Division; in center is Dr. Nelson K. Richtmyer, chairman of the award committee
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MANY CHEMISTS. During the exposition's three days, droves of chemists strolled through the exhibits. One focal point: Enjay (lower left), where lucky winners got a model tank car
LAST MINUTE CHECK. Just to make sure, Walter Coulter, president of Coulter Co., with a company engineer, goes over the electronics of Coulter Counter particle size analyzer
BIG BLOW. Hurricane Donna, which blew into town with most of the chemists, played havoc with some exhibitors' plans. Hardest hit: Dow, which could only put out what the salesmen had in their suitcases
FREE TEA. Lipton Tea set up a "rest and recuperat i o n " area on the balcony overlooking the showBeverage: "chemist's delight," a mixture of tea and fruit punch
Vendors Display Wares to Chemists by the Thousands
GLASS MAZE. Scientific Glass Apparatus provides more proof of trend toward easier operation of everything 26
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Exhibitors from the chemical industry and its suppliers had a good chance to reach chemists and chemical engineers at the ACS meeting in New York. The medium: Chemical Exposition—U.S.A.—1960, sponsored by the ACS New York Section and held during the middle of meeting week. Visitors to the exposition—and from the looks of the crowds gathered around the most popular booths, they included most of the 13,000 or so meeting attendees—had a good chance to correlate the number of new products that has been bombarding them from instrument makers, chemicals producers, lab equipment suppliers, and specialties makers. One obvious conclusion: The high cost of people is leading to time- and labor-saving de-
vices of all sorts. Automatic devices of all sorts are now available for such things as pH, polarographic, and chromatographic measurements. And even that mundane stand-byweighing—is becoming automatic, as electronics takes over more and more of the repetitive operations involved. But the same trend is evident in other phases of the chemical industry. Process units are "packaged," components of instrument systems are now put together into full systems by the vendors, containers are more streamlined to save time and effort. J. T. Baker, for example, had on hand its new aluminum, screw cap container for ether and other relatively expensive reagents sensitive to contaminants from the atmosphere.
