G. F. Widhopf, L. Glatt, and R. F. Kramer, Potential Ozone Column Increase Resulting from Subsonic and Supersonic Aircraft NO, Emissions, AZAA J., 15, 1322-1 330, September 1977. A current and quantitative assessment is not available as of this writing (April 5 , 1978). Broderick, however, discusses the situation as of July 1977, noting the effects of the Howard and Evenson measurement. The NAS report (December 1977) discusses briefly (and, for currently projected fleets, largely dismisses) aircraft NO, effects on ozone. Further changes can of course still be expected, as large uncertainties remain. The above list does not include references to the large, important and interrelated body of literature published in recent years on stratospheric chlorine and its effects on ozone. The listed NAS report, however, refers to previous work and indicates recent developments in the area. R. C. Oliver IDA Arlington, Va. 22202
Reply to R. C.Oliver Dear Sir: Oliver is to be congratulated on a succinct presentation of the latest findings with regard to the effects of aircraft pollutants on ozone. I had hoped that ES& T readers would learn from my article not what are the current findings but, as I stated in the section labelled assessment ( E S 6 T, March 1978, p 274), “whether there was a reasoned path from the earliest conclusions of no effect, through a possible 50% reduction of ozone, to the consensus generally reached in the U S . by the end of 1974 of 8-15% global ozone reduction. . .I’
Revnold Greenstone ORI, Inc. Silver Spring, Md. 20910
Liquid waste incinerators Gentlemen: We read with interest your article “The fire next time” (ES&T, February 1978, p 134). Overall, it appeared that your survey of companies building liquid waste incinerators provided a good snapshot of the state of the industry, although excluding the John Zink Company. Zink has been designing and building liquid incineration systems since 1961. We maintain the most complete test facility for incineration of toxic liquid and gaseous wastes in the industry, and have over 500 waste incinerator systems in the field at this time.
If you’re looking for economical weighing, look at the Mettler electronic top-loading balances. The no-frill PB models are best for people who want fast, accurate weighing but do not require digital outputs and other extra features. They’re ideal for routine weight determinations and checkweighing. Just place the sample on the pan and read the 7-seg ment digital result. For non-routine weighings, a Mettler PL model should beyour choice. Some PL balances are available with a Net Total Display feature that gives you a separate display of intermediate net totals when weighing in formulas. Or you can also get a digital output for connection to peripheral equipment, such as a calculating printer. All PL balances can easily adapt to less-than-perfect weighing environments because they have an external switch to adjust integration time. For complete details, circle the reader service number, or contact us directly: Mettler Instrument Corporation, Box 71, Hightstown, NJ 08520.
Electronic balances and weighing systems Thermal analysis instruments Titration instruments Automated laboratory systems
Dan Banks John Zink Company Tulsa, Okla. 74105 CIRCLE 8 ON READER SERVICE CARD
Volume 12, Number 6 , June 1978
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