5,5’-hexachlorobiphenyl on (a) 3.18;on (b) 3.21.R , value of peak 6 on (a) 3.19;on (b) 3.22.Ir spectrum: Figure 3A. Nmr spectrum: 2 H (d), 6 = 7.61,J N 0.3 cps; 2H (d), 6 = 7.36, J N 0.3 cps. 2,2‘,3,4,4‘,5’-Hexachlorobiphenyl was prepared from an equimolecular amount of 2,4,5-trichloroiodobenzene and 2,3,4-trichloroiodobenzene. Mp : 78.5-80°C. R t value of 2,2’,3,4,4’,5’-hexachlorobiphenylon (a) 3.75; on (b) 3.88. R,value of peak 8 on (a) 3.77;on (b) 3.90.Ir spectrum: Figure 3B. Nmr spectrum: 1H (d), 6 = 7.62,J 0.3 cps; 1H (d), 6 = 7.50,J= 8.25CPS; 1H (d), 6 = 7.35,J- 0.3 cps; 1H (d), 6 = 7.10,J = 8.25 CPS. By-products: 2,2’,4,4’,5,5’-hexachlorobiphenyland 2,2‘,3,3’,4,4’-hexachlorobiphenyl.Mp: 145.5-146.5”C.R, value: on (a) 4.44; on (b) 4.69. Ir spectrum (KBr): strong 1430, 1353, 1185, 792; medium 1370, 1168, 881, 830, 819, 751. Nmr spectrum: 2 H (d), 6 = 7.50,J = 8.25 cps; 2 H (d), 6 = 7.10,J = 8.25 CPS. 2,2’,3,4,4’,5,5 ’-Heptachlorobiphenyl was prepared from an equimolecular amount of 2,4,5-trichloroiodobenzene and 2,3,4,5-tetrachloroiodobenzene.Mp : 109-1 10°C. R , value of 2,2’,3,4,4’,5,5’-heptachlorobiphenyl on (a) 6.48;on (b) 6.52. R, value of peak 1 1 on (a) 6.49;on (b) 6.53.Ir spectrum: Figure 3C.Nmr spectrum: 1H (d), 6 = 7.64,J - 0.3cps; 1H (d), 6 = 7.35,J- 0.3CPS;1H (s), 6 = 7.30. By-products: 2,2’,4,4’,5,5 ’-hexachlorobiphenyl and 2,2‘,3,3‘,4,4‘,5,5‘-octachlorobiphenyl.Mp: 152-153°C. R , value on (a) 13.18;on (b) of 2,2’,3,3’,4,4’,5,5’-octachlorobiphenyl 13.18. Ir spectrum: strong 1401, 1341; medium 1181, 1097, 880, 848,831, 782,686.Nmr spectrum: 2 H (s), 6 = 7.31. 2,2’,3,3’,4,4’,5-Heptachlorobiphenylwas prepared with an equimolecular amount of 2,3,4-trichloroiodobenzeneand 2,3,4,5-tetrachloroiodobenzene. Mp: 134.5-135.5“C. R 2value of 2,2‘,3,3’,4,4‘,5-heptachlorobiphenyl on (a) 7.73; on (b) 7.92.R 2value of peak 12 on (a) 7.68;on (b) 7.89.Ir spectrum: Figure 30. Nmr spectrum: 1H (d), 6 = 7.51,J = 8.25 cps; 1H (s), 6 = 7.32;1H (d), 6 = 7.09,J= 8.25CPS. By-products: 2,2’,3,3’,4,4’-hexachlorobiphenyl and 2,2’,3,3’,4,4’,5,5 ’-octachlorobiphenyl. N
Results and Discussion
From the obtained nmr, ir, and glc data, it can be concluded that the two hexachlorobiphenyls and two heptachlorobiphenyls are major constituents of the investigated Phenochlor D P 6 chlorinated biphenyl mixture. Moreover, the melting points of the isolated fractions showed no depression when mixed with the corresponding synthetic material. The symcan be metric compound 2,2‘,4,4‘,5,5‘-hexachlorobiphenyl obtained in a pure form by a relatively simple synthesis and will be used for toxicity studies. The identification study has been restricted to the Phenochlor mixture. As far as the gas chromatograms are concerned, comparable products of other manufacturers have been found similar (Koeman et al., 1969; Figure 1). Acknowledgment We thank R. J. Belz and R. J. C. Kleipool for their valuable advice. Literature Cited Acker, L., Schulte, E., Naturwissenschaften 57, 497 (1970). Bagley, G. E., Reichel, W. L., Cromartie, E., J . Ass. Ofic. Anal. Chem. 53, 251 (1970). Bailey, S., Bunyan, P. J., Fishwick, F. B., Chem. Ind., (London) 705 (1970). Gustafson, C. G., ENVIRON. SCI.TECHNOL. 4, 814 (1970). Holden, A. V.,Nature 228, 1220 (1970). Holden, A. V.,Marsden, K., ibid. 216, 1274 (1967). Holmes, D.C., Simmons, J. H., Tatton, J. 0. G., ibid. p 227. Jensen, S., New Sci. 32, 612 (1966). Koeman, J. H., Noever de Brauw, M. C. ten, Vos, R. H. de, Nature 221, 1126 (1969). “Organic Reactions,” Vol 11, p 243,Wiley, New York, N.Y., 1944. Vos, J. G., Koeman, J. H.,Maas, H.L. van der, Noever de Brauw, M. C. ten, Vos, R. H. de, Food. Cosmet. Toxicol. 8, 625 (1970). Vos. R. H. de. Peet. E. W.. Bull. Enciron. Contam. Toxicol. 6 , 164 (1971). ’ Westoo, G., NorCn, K., Anderson, M., Var Foeda 22, 11 (1970). Receicedjor reaiew March 8, 1971. Accepted July 12, 1971.
A Smog Chamber Study Comparing Blacklight Fluorescent Lamps with Natural Sunlight John L. Laity Emeryville Research Center, Shell Development Co., Emeryville, Calif. 94608
Photochemical smog is commonly studied in irradiation chambers by using blacklight fluorescent lighting, which differs in several respects from natural sunlight. A direct comparison of the effects of artificial and natural sunlight has been obtained in a glass chamber. Since only slight discrepancies are observed in comparable experiments with blacklight or sunlight irradiation, the differences between blacklight lamps and natural sunlight do not dramatically influence photochemical smog formation with the systems investigated. This finding justifies the conventional use of blacklight irradiation in laboratory investigations of photochemical smog.
1218 Environmental Science & Technology
M
uch of the present knowledge about photochemical smog comes from studies conducted in irradiation chambers with either fluorescent lamps (Altshuller, 1966 ; Altshuller and Bufalini, 1965,1971 ; Heuss and Glasson, 1968; Katz, 1970) or actual sunlight (Altshuller et al., 1970). Artificial sunlight obtained from fluorescent lamps differs appreciably from natural sunlight, and these differences in the light source conceivably could affect photochemical smog formation. One comparison of the effects of artificial and natural sunlight was presented by Stephens et al. (1967),who used gas-liquid chromatography (glc) to follow hydrocarbon disappearance with a sample of urban air in two glass vessels. One vessel was exposed to the sun for an entire day, and the
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other was irradiated with blacklight fluorescent lamps for the same period one day later. In these experiments, the olefins (especially propylene) disappeared somewhat more rapidly with actual solar irradiation. Yet, a difference in the light source was not the only disparity between the t y o experiments. The spectral distribution (centered at 3550 A) of blacklight lamps is somewhat different from the uv portion of natural sunlight (Tuesday, 1961). Moreover, unlike sunlight, the fluorescent lamps used in many smog chamber studies have a rapid stroboscopic effect and do not give a constant output of light. An oscillogram (Figure 1) of the light modulation at 120 Hz (with 60 Hz power) of a blacklight fluorescent lamp indicates substantial, repetitive variations in the light intensity. The modulation of the alternating-current lamps is dependent on a number of factors including the ballasts, phasing of the current, and the phosphorescence qualities of the lamps. However, actual solar irradiation does not feature the rapid fluctuations of light intensity that are characteristic of ac fluorescent lamps. As many others have noted, intermittent illumination may influence light-induced reactions, especially chain processes, by affecting the concentrations of reactive intermediates (Calvert and Pitts, 1966). Experimental The vessel used for these studies is a 22-1. borosilicate glass spherical flask fitted with a glass cap (which has three sampling ports) and a magnetically driven, all-glass stirrer. (Grasley et al., 1969). The chamber was cleaned between experiments by overnight evacuation while warming the walls to -50°C. Indoors, the vessel was irradiated at 23 "C with three blacklight lamps (Rayonet 3500 A, with each lamp approximately 12.5 W) in a commercially available Rayonet reactor (Southern New England Ultraviolet Co., Middletown, Conn.). Outdoor studies were conducted in the San Francisco Bay area at Emeryville, Calif., from 11 A.M. to 3 P.M. on several clear, sunny days in September 1970. Since the objective of these experiments was a comparison of the effects of natural and artificial sunlight, all other variables (temperature, chamber dilution rate, etc.) were matched and held as constant as possible. The indoor and average outdoor light intensities gave about the same rate ( K d )of photolytic decomposition of NOZ(2 ppm) in nitrogen. The results of several outdoor Kd
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determinations ranged from 0.15-0.3 min-l, depending on the day and time, but the average value ( = t u ) was 0.22 0.05 min-l ;the indoor Kd was 0.22 f 0.02 min-'. The experiments were followed by conventional experimental techniques (Grasley et al., 1969). Hydrocarbons were analyzed by glc with a flame ionization detector, peroxyacetyl nitrate was monitored by glc with an electron capture detector (Darley et al., 1963; Stephens, 1969), and hourly readings of total oxidant were measured coulometrically with a commercial ozone meter (Mast Development Co., Davenport, Iowa). The response of the meter to nitrogen dioxide was subtracted to give the oxidant values. Nitrogen dioxide was determined colorimetrically with 250-ml grab bottles and Saltzman's reagent (Saltzman, 1954, 1965). The formaldehyde level was determined at the end of each run by the chromotropic acid method (Altshuller et al., 1961 ; Sleva, 1965; West and Sen, 1956). During sampling, pure air was added to maintain constant pressure, and the analytical determinations were corrected for the resultant dilution. High-purity air (Air Products and Chemicals ultrapure air containing
