Radiocarbon Traces Air Mass Movement
how to
Carbon-14 from nuclear weapons testing used to follow atmospheric mixing
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Filters, fabrics and containers do double duty when coated with ac tivated charcoal paint. Sprayed or brushed on it adsorbs odors in stead of producing them. Can be washed off after saturation. Try a quart or a tank car.
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We supply a complete line of acti vated carbons for every purpose; design and prefabricate complete purification, separation, and re covery systems to meet your par ticular needs. Write for Bulletin J-120 and recommendations on your specific application. Barnebey-Cheney, Columbus 19, Ohio.
Barnebey Cheney 44
C&EN
NOV.
2 0,
1961
Residence time of radioactive materials released into the stratosphere by nu clear weapons testing is about seven and one-half years, according to stud ies by Dr. G. J. Fergusson, associate professor of geophysics at University of California, Los Angeles. Dr. Fergusson told the National Academy of Science's meeting at UCLA early this month that radio carbon can be a better tracer of at mospheric air mass movements than particulate fission products are. The latter are rapidly removed by precipi tation, particularly from the lower troposphere, whereas radiocarbon in its gaseous form as carbon dioxide will stay in the atmosphere for several years. Dr. Fergusson estimates that the total energy release from nuclear weapons testing during the period 1954-58 was 180 megatons, TNT equivalent. This testing produced about 19 Χ 10 27 atoms of C 14 , distrib uted 52 r'( in the stratosphere, 35% in the troposphere, 1 1 % in the ocean, and 2% in the biosphere. Earlier Tests. Dr. Fergusson points out that during the period 1960-61 the C 1 1 content of the atmosphere would be mainlv that due to earlier
tests at low latitudes in the Pacific; the lapse of several years since injec tion means that this radiocarbon has attained a rather uniform distribution. He calculates the transfer of radio carbon from the troposphere to ocean and biosphere during 1960 to be 1.3 X 10-" atoms. Since the measured C H content of the troposphere was relatively constant during this period, input from the stratosphere must have been a similar amount. The residence time in the stratosphere of seven and one-half years is then obtained by di viding the estimated number of radio carbon atoms in the stratosphere by the annual transfer rate to the tropo sphere. The data for the period 1959-61 also support the theory that most of the transfer of material from the strat osphere to the troposphere takes place during the spring in polar regions. In the summer of 1959 the high northern latitudes showed a higher C 14 con tent, but this difference declined rap idly, presumably due to mixing. Weapons Testing. Since the ma jority of nuclear weapon tests have been in the Northern Hemisphere, it is not surprising that C 14 levels have been higher in the Northern Hemi-
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45
sphere's troposphere. The Southern Hemisphere has only lagged about one year behind the Northern Hemisphere in troposphere C 1 4 level, so there must be transfer across the equator in about that same period of time. Finding suitable ground level at mosphere sampling sites has been diffi cult because of the large amount of nonradioactive carbon dioxide from fossil fuels that is injected into the atmosphere by large cities and in dustrial centers. High altitude sam pling from jet aircraft would overcome this problem, but this has not been practical until now. The conventional method has been to collect a sample on the exposed surface of sodium hydroxide solution in an open tray. But this requires a minimum of three days of continuous sampling to collect enough sample for C 14 analysis. Recently designed sam plers based on a molecular sieve have been used very successfully in jet air craft at 30,000 feet, Dr. Fergusson says. These samplers will collect as much as 15 liters of atmospheric car bon dioxide in two hours.
Cellulose Cross-Linked at High Temperature when Swollen Nonvolatile, nonreactive watersoluble compound swells cotton, keeps it swollen when hot and dry Cellulose has been cross-linked in the swollen state, but in the absence of water and at a high temperature, by Dr. Emery I. Valko and Kunjvihari M. Limdi of Lowell Technological In stitute, Lowell, Mass. This is a com bination of conditions that until now hasn't been used in cross-linking cellu lose in cotton—now done on a large scale commercially to make wrinkleresistant wash and wear fabrics. Normally, cotton becomes swollen only by being wet. So if it is crosslinked in this condition, the reaction must take place at a relatively low tem perature—below the boiling point of water. It can be cross-linked at higher temperatures, but then the water is driven off and the cotton fibers are not swollen, but are collapsed. The type of wrinkle resistance a fabric has depends upon whether its fibers are cross-linked in the swollen or in the collapsed state. The cross-linking agent used in the experiments. Dr. Valko told the 10th 46
C&EN
N O V . 2 0, 1 9 5 1
Chemical Finishing Conference of the National Cotton Council of America in Washington, D.C., was 1,3 bis(hyusually droxymethyl ) -2-imidazolene, called dimethylol ethylene urea or DMEU, and widely used in the tex tile industry. To get the cotton into the swollen state and keep it there at temperatures high enough to drive the water out of the fiber, a nonvolatile, nonreactive water-soluble compound was added to the reaction mixture. Some of the compounds used were 2,5,8,11,14-pentaoxapentadecane, triethylene glycol monomethyl ether, and monomethyl ether of polyethylene glycol. The temperature during curing— that is, cross-linking—was 150° C. Best results came when the cotton was first mercerized and saturated with the solvent-reaction mixture without any intermediate drying step. Properties of the high temperature cured fabric were no better than those of fabrics treated in the ordinary way. But Dr. Valko points out that high temperature curing, involving crosslinking in the swollen state without any water, has a potential use. It is a possible means of making the in terior of the fiber accessible to watersoluble compounds at a high tempera ture. In addition, it might make the interior of the fiber accessible to waterinsoluble but solvent-soluble reactants applied, for example, in the form of an aqueous emulsion. This opens up new7 possibilities for many chemicals not presently used in textile finishing.
Interested personal service— always— when you buy from Eastman
For the Protective Coatings Industry Solvents acetone ethyl acetate 2-ethylhexyl acetate isopropyl acetate isobutyl acetate η-butyl acetate η-butyl alcohol isobutyl alcohol 2-ethylhexyl alcohol methyl isoamyl ketone (MIAK) Tecsol® (95%
proprietary ethyl alcohol)
Film Formers cellulose acetate cellulose acetate butyrate
Modifier sucrose acetate isobutyrate (SAIB)
Plasticizers dimethyl phthalate diethyl phthalate di-(methoxyethyl) phthalate dibutyl phthalate di-isobutyl phthalate plasticizer 84 —an octyl butyl phthalate
BRIEFS Fluorescence is being used to meas ure pesticide residues in plant and animal tissue, according to Dr. D. MacDougall, Chemagro Corp., Kansas City, Mo. Using modern instruments equipped with xenon arc lamps, radia tion of different wave lengths can be isolated. Thus the scientist can se lect any desired wave length for ex citation purposes, or any particular fluorescent band required. Principal advantage of fluorescence is its high sensitivity. Besides carrying out pro cedures on fluorescent substances or those which can convert to highly fluorescent materials, the residue to be measured may be used as the limit ing factor in a reaction producing a fluorescent material, he adds.
dioctyl phthalate (DOP) dioctyl isophthalate (DOIP) Texanol isobutyrate Texanol glycolate Texanol benzoate polymeric plasticizer NP-10
For properties and shipping information on these and other Eastman p r o d u c t s , see Chemical Materials C a t a l o g , p a g e 2 2 5 , or Chemical Week Buyers' Guide, page 113.
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