REPORTS in the construction of industrial water-cooling towers and the corre sponding allowable design stress values for these grades in framework design. And it has spent 5 years studying wood maintenance (Bul letin WMS-104). One result of the latter is that, to date, four chem ical preservatives seem definitely to protect redwood, fir, cedar, and pine against biological attack in cooling towers. They are: creo sote, Chemonite (J. H. Baxter & Co.), and Erdalith and Celcure (both Koppers). Because of price and availability of redwood, plus changing plant operating practices (which change the chemistry of recirculating water), we may one day see treated fir, cedar, and per haps other materials competing with redwood in cooling towers. CTI's next standards push will be on large, propeller-type fans and their speed reducer gears. Fans must move large volumes of air at low pressures and velocities, and there is little basic technology in the field. Right-angle gears must make about a 10 to 1 reduction, working in a hot, saturated, corrosive vapor. Lubrication is one of several prob lems here, but a good deal of per tinent technology exists and CTI expects to develop its standards as modifications of present industrial gear .standards.
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Paul Bunyan Chemistry Researchers are trying to find out what makes chemical debarking work
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ARK, the "fabulous waste," has now found its way into chemical markets (I&EC, January 1956, pp. 75 A—76 A). And wood chemistry, generally, is becoming more im portant (I&EC, March 1956, pp. 7A-10A). But chemical mysteries in the field still await additional detective work. Chemical debarking is a good ex ample—researchers are puzzled over the mechanism that causes arsenites
and sulfamic acid to loosen bark from trees. Chemical debarking, practiced on a commercial basis for more than 8 years, is still hardly more than an established empirical process. Pulp and paper companies in the United States annually treat more than 50,000 cords of pulpwood in this way, without really knowing why or how their process works. How It's Done
In its simplest form chemical de barking works this way: A band of bark is removed from the tree early in spring and the exposed sapwood is painted with a solution of sodium arsenite. The woodsman's tools may be simple or elaborate, but so far the only chemicals that give satisfactory results are soluble ar senic compounds. Within 10 days after a chemical application, the tree dies. It is almost impossible to peel a living tree during the period in which chemical debarking takes place (from September until the following sum mer). (Six months or a year later, bark may be peeled from the tree with minimum effort.) Although not much is known about the process, chemical debarking has one big advantage: It extends the time of easy peeling from a 2-month period in the spring to almost a year-round basis. Almost all trees commonly used for pulpwood respond to this treat ment. (Ash is an exception, as results are erratic and only occa sionally will this species peel well.) But other natural conditions pro hibit chemical debarking of certain tree species. For example, decay and insect attack are unusually severe after treatment of white pine in the
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North and pulpwood trees in the South. Cost of treatment will vary with the volume of pulpwood handled and tree diameter. Most foresters say it is economical to work with a large volume of trees bigger than 10 inches in diameter. On this basis, one would expect to consume an average of 0.05 gallon of sodium arsenite and 0.6 man-hour per cord. This year foresters in the United States will probably use 10,000 gallons of 40% sodium arsenite solution; their Canadian brothers about 4000 gallons. Where We Stand
At New York State University, foresters recently completed a 4-, year cooperative project, trying to learn the whys and wherefores of chemical debarking. They not only found out a great deal about funda mental physiological aspects of the process; researchers developed some improved application techniques. In the past other researchers have tested hundreds of chemicals, hoping to find a compound which is nontoxic to animals. But they couldn't turn up a suitable substitute for sodium arsenite. The Syracuse group, in looking at organic arsenicals (such as monoethanolamine arsenite), found a few compounds that may actually be more effective than sodium arsenite. Because of their odor and probable lack of "saltiness," these compounds might be less attractive to wildlife. When the door opens to this new possibility, more research can be expected in this field, with the hope of providing protection to forest wildlife. H.W.Hr
I/EC VOL. 48, NO. 12
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DECEMBER 1956
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