Lasers analyze air - C&EN Global Enterprise (ACS Publications)

Inside the cell is a sensitive microphone that converts changes in air pressure into electrical signals. To measure quantity of pollutants, the laser ...
1 downloads 0 Views 204KB Size
Chemical world This week a rate approaching the traditional 7 or 8% could quickly kick this capacity utilization comfortably past 80%. This, in turn, could set the industry up for an upsurge in capital spending starting in 1973 and possibly peaking in 1975 at about $4.5 billion to $5 billion per year. Expectations of no growth in basic chemical industry capital spending this year or next are in line with the findings of other surveys. For instance, the latest quarterly Securities and Exchange CommissionDepartment of Commerce review estimates that the chemical and allied products industry will spend $3.36 billion on new plants and equipment in the U.S. in 1971, a 2% drop from $3.44 billion spent last year. (The chemical and allied products industry is a grouping that includes drug, fertilizer, paint, soap, and specialty chemical makers as well as basic chemical makers.) The latest quarterly Conference Board survey of capital appropriations also indicates no growth in store for chemical spending. New appropriations by chemical makers of $719 million in the first quarter of this year were down 8% from the year-earlier level. At the end of the first quarter, the industry's unCAPITAL SPENDING: spent appropriations were lingering Tight rein in 1972 at $2.74 billion—the lowest level in Basic chemical makers are keeping two years. a tight rein on capital spending this year. And it's apparent that POLLUTION: they intend to do the same next year, according to the latest survey Lasers analyze air by C&EN's senior editor Michael A tunable infrared laser system for Heylin of capital investment com- measuring nitrogen oxide gases in mitments and plans of major do- air in concentrations as low as 10 mestic chemical companies. p.p.b. has been developed by Bell Total worldwide spending of U.S.- Laboratories scientists. The sysbased basic chemical makers will tem could lead to rapid on-the-spot likely total about $3.1 billion both identification of pollutant gases in this year and next—equaling the air and could replace time-consumspending level of 1970. If the in- ing, less sensitive tests currently dustry sticks to these plans, used in analyzing air samples. it means that 1972 will be the sixth Bell Labs' system, designed by year in a row in which spending Dr. C. Kumar N. Patel and Dr. will have been at, or below, the Lloyd B. Kreuzer, use a carbon record $3.15 billion that C&EN esti- monoxide infrared laser whose mates the industry spent in 1966. beam frequency can be controlled Continued spending restraint by an electromagnet and indium both this year and next may finally antimonide semiconductors. The laser beam, interrupted at allow the excess plant capacity built during the industry's spending regular intervals by a rotating shutsurge in the late 1960's to be ter causing a pulsing action, is directed into an optoacoustic abbrought into full use. Today the basic chemical indus- sorption cell containing the air try is using its plants at an average sample. Inside the cell is a sensiof about 77% of capacity. A re- tive microphone that converts covery in growth of chemical pro- changes in air pressure into elecduction from the 2 or 3% annual trical signals. To measure quantity of polrate of the past couple of years to

up 6337 scientists who are out of work and looking for jobs. About 1500 listed education as their last job field; 1000, industrial products and processes; 700, defense; and 300, space activities. Of the unemployed scientists, 42°/o were in California, New York, Massachusetts, New Jersey, and Pennsylvania. The majority of the unemployed scientists are less than 40 years old, NSF says, adding that scientists under 30 have the highest unemployment rate (5.3%) of any age group. The rate for women is 5.2%, compared to 2.3% for men, and for doctorates it's 1.4%, compared to 3.7% for master's and 3.5% for bachelor's degree holders. NSF figures are based on responses from 253,078 scientists to whom queries were mailed on April 1, and the findings "represent minimum absolute numbers of unemployed." The Office of Science and Technology, which requested NSF to conduct the survey, will probably use the numbers in formulating ways to cope with the unemployment problem. A similar survey of engineers is under way by the Engineering Manpower Commission.

12 C&EN JULY 12, 1971

lutants, the laser is tuned to a frequency at which the known pollutant absorbs light and then is directed at the sample. Light energy absorbed by the gas increases the temperature and pressure of the sample in direct proportion to the amount of pollutant present. The pressure increase is picked up by the microphone, and the strength of the resulting electrical signal can be recorded on a meter, oscilloscope, or graph paper. Bell Labs' experimental system is not portable; thus, air samples are collected in flasks and returned to the laboratory for testing. Dr. Patel and Dr. Kreuzer believe that present technology will permit design of portable equipment for onthe-spot air pollution tests. Other laser systems are being developed for measuring air pollutants. For example, the Environmental Protection Agency is evaluating an IR laser system developed by Harvey Tannenbaum, of Edgewood Arsenal, Md. This system involves placing a laser and detector in open air, using a distant reflector to bounce the laser beam back to the detector. Other candidates for routine laser analysis of air pollutants include a system based on ultraviolet lasers and Raman scattering, developed by Mr. Tannenbaum, and systems based on tunable dye and diode lasers.

Kreuzer and Patel collect air sample