IMPI chairman Voss Electrical engineer from Edmonton
surface becomes hot and heat moves inward. Microwaves, on the other hand, produce rapid and uniform heat ing throughout the entire substance. And microwaves do not give up their energy until they come into contact with the particles. The Federal Communications Com mission has set aside four frequencies for microwave use in industrial, sci entific, and medical applications. Commercial cooking is now by far the biggest market for industrial micro wave equipment. Microwaves are used for making potato chips, dried foods, and precooked meals. Micro wave ovens are widely used in restau rants and institutions for heating pre cooked meals rapidly. But other industries are also study ing microwaves. The wood products industry, for example, is interested in them as a means of curing adhesive layers as well as epoxy and polyester surface coatings. The chemical indus try might use them to initiate chemi cal reactions. The pharmaceutical in dustry is installing equipment to dry heat-sensitive compounds. IMPI will serve as a forum for the exchange of information on micro waves. Membership in the new in stitute, already exceeding 200, should increase rapidly. The next IMPI sym posium will be at Stanford next March.
Ν analysis widely applicable A new method for determining nitro gen content in fertilizers was disclosed last week by Dr. Charles W. Gehrke, University of Missouri professor of ag ricultural chemistry, at the 80th an nual meeting of the Association of Official Analytical Chemists (AOAC), in Washington, D.C. (AOAC, repre 38 C&EN OCT. 17, 1966
senting chemists from federal, state, and city agencies, as well as from drug companies, chooses official "standard" methods of analysis for determining the composition of a wide variety of substances—for example, fertiliz ers. ) Until now, variations of the classic Kjeldahl method have resulted in five separate methods required for deter mining nitrogen in different types of fertilizer. But the new method is ap plicable to all fertilizers and to all forms of nitrogen, Dr. Gehrke says. The method utilizes untreated chro mium metal powder in an acid me dium to reduce nitrates to ammonia, which is then distilled and measured. Work is being completed on making the technique automatic. In association with Dr. Gehrke in developing the analysis were James P. Ussary, Paul R. Rexroad, and William L. Spangler, all of Missouri, and Car rol H. Perrin of Canada Packers, Ltd., Toronto, Ont. According to Dr. Gehrke, the com prehensive method for analyzing total nitrogen can be applied to solid and liquid fertilizers, including those with high Cl/NOg ratios. The method also has broad applications to organic, in organic, organic-inorganic combina tions, and biological samples, he adds. The new method compares favor ably with older methods in accuracy and precision, and it holds a distinct advantage in its rapidity. It's about 40% faster in analysis time than pre vious methods, according to Dr. Gehrke. He and Mr. Ussary, along with James H. Baumgartner, have also de veloped an automatic photometric method for analyzing all forms of fer tilizer phosphorus. This method uses a Technicon AutoAnalyzer to deter mine phosphorus, complexed as phosphomolybdovanadate, in concentra tions of 2.0 to 4.5 mg. P 2 0 5 per 100 ml. at a sampling rate of 40 analyses per hour. An AOAC automatic flame photo metric method for analyzing potassium has also been developed by Dr. Gehrke and his coworkers. Automatic analy sis has decreased both the time and manpower needed for phosphorus and potassium determinations. "Under analysis methods we used iive years ago," Dr. Gehrke says, "we would handle 100 samples a week and results would not be available for sev eral weeks. With our new methods we can make 150 analyses in two days and results are available in less than a week." Should AOAC accept the compre hensive nitrogen method, Missouri will have supplied "standard" methods for the three major constituents in fertiliz ers—nitrogen, phosphorus, and potash.
GE has transparent ceramic A transparent ceramic material that can withstand temperatures more than twice as high as glass can has been de veloped at General Electric. The ce ramic has a melting point in excess of 4000° F., while glass softens be tween about 2000° and 2600° F., GE's Dr. Richard C. Anderson, inventor of the material, and Dr. Paul J. Jorgensen told last week's American Ceramic Society meeting, at University Park, Pa. Dr. Anderson and Dr. Jorgensen de scribed the new material, dubbed Yttralox ceramic, as a solid solution of about 90% yttrium oxide and 10% thorium oxide. In making the mate rial, the oxide powders are pressed into the desired shape and then sintered at about 4000° F. This heat treat ment removes the microscopically small pores from between the powder particles. Such pores scatter light, causing opacity in conventional ceram ics. The end result of this treatment, the GE scientists say, is a single-phase, polycrystalline material with a grain size normally between 10 and 50 mi crons in diameter. Yttrium oxide has a cubic crystal structure, thus light is not scattered at grain boundaries in the Yttralox ceramic. This property, they note, combined with the absence of second phase and pores, imparts an "exceptional transparency" (with pol ishing) to visible and infrared light. The transmission cutoff in the ul traviolet range occurs at 0.24 micron and in the infrared range at about 9 microns. Its spectra show no marked absorption bands; throughout the visi ble range, light absorption is as low as 3% for a 2-mm.-thick sample. Inci dent light not absorbed or reflected from the surface is transmitted with minimum distortion. Although the index of refraction of the ceramic is high, about 1.91 at the sodium D line wave length (589.3 m/x), the material's optical dispersion is very low. "No other known material offers the spectrum of properties found in Yttra lox ceramic," Dr. Arthur M. Bueche, vice president in charge of GE's re search and development center, Sche nectady, N.Y., commented at the ce ramic meeting. It can be fabricated inexpensively, he adds. Several possible applications for Yt tralox ceramic include scientific, indus trial, and military fields. One applica tion may come in improved high-inten sity incandescent and discharge lamps. The ceramic may also find uses as an IR window for heat-seeking rockets, as a window into high-temperature fur naces, and in lenses for microscopes used in the study of molten samples.
