It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Some features of ATS will be disabled while you continue to use an ad-blocker.
3.1 NATURE OF POLLUTANT Benzene is a clear, colorless, aromatic hydrocarbon that has a characteristic sickly sweet odor. It is both volatile and flammable. Chemical identification information for benzene is found in Table-3-1. Selected physical and chemical properties of benzene are presented in Table 3-2 .4-7 Benzene contains 92.3 percent carbon and 7.7 percent hydrogen (by mass). The benzene molecule is represented by a hexagon formed by six sets of carbon and hydrogen atoms bonded together with alternating single and double bonds. 3-2 TABLE 3-1. CHEMICAL IDENTIFICATION OF BENZENE Chemical Name Benzene Synonyms Benzol, phenyl hydride, coal naphtha, phene, benxole, cyclohexatriene Molecular formula C H 6 6 Identification numbersa CAS Registry 71-43-2 NIOSH RTECS CY 1400000 DOT/UN/NA UN 1114; Benzene (Benzol) DOT Designation Flammable liquid Source: References 4 and 5. a Chemical Abstract Services (CAS); National Institute of Occupational Safety and Health (NIOSH); Registry of Toxic Effects of Chemical Substances (RTECS); Department of Transportation/United Nations/North American (DOT/UN/NA). The chemical behavior of benzene indicates that the benzene molecule is more realistically represented as a resonance-stabilized structure: in which the carbon-to-carbon bonds are identical. The benzene molecule is the cornerstone for aromatic compounds, all of which contain one or more benzene rings.8 Because of its resonance properties, benzene is highly stable for an unsaturated hydrocarbon. However, it does react with other compounds, primarily by substitution and, to a lesser degree, by addition. Some reactions can rupture the molecule or result in other groups cleaving to the molecule. Through all these types of reactions, many commercial chemicals are produced from benzene.8 The most common commercial grade of benzene contains 50 to 3-3 TABLE 3-2. PHYSICAL AND CHEMICAL PROPERTIES OF BENZENE Property Value Molecular weight 0.17 lbs (78.12 g) Melting point 41.9(F (5.5(C) Boiling point at 1 atmosphere (760 mm Hg) 176.18(F (80.1(C) Density, at 68(F (20(C) 0.0141 lb/ft3 (0.8794 g/cm3) Physical state (ambient conditions) Liquid Color Clear Odor Characteristic Viscosity (absolute) at 68(F (20(C) 0.6468 cP Surface tension at 77(F (25(C) 0.033 g/cm3 (28.18 dynes/cm3) Heat of vaporization at 176.18(F (80.100(C) 33.871 KJ/Kg·mol (8095 Kcal/Kg·mol) Heat of combustion at constant pressure and 41.836 KJ/g (9.999 Kcal/g) 77(F (25(C) (liquid C H to liquid H O and 6 6 2 gaseous CO ) 2 Odor threshold 0.875 ppm Solubility: Water at 77(F (25(C) Very slightly soluble (0.180 g/100 mL, 1800 ppm) Organic Solvents Soluble in alcohol, ether, acetone, carbon tetrachloride, carbon disulfide, and acetic acid Vapor pressure at 77(F (25(C) 95.2 mm Hg (12.7 kPa) Auto ignition temperature 1044(F (562(C) Flashpoint 12(F (-11.1(C) (closed cup) Conversion factors (Vapor weight to volume) 1 ppm = 319 mg/m3 at 77(F (25(C); 1 mg/L = 313 ppm Source: References 4, 5, 6, and 7. 3-4 100 percent benzene, the remainder consisting of toluene, xylene, and other constituents that distill below 248(F (120(C).4 Laboratory evaluations indicate that benzene is minimally photochemically reactive in the atmosphere compared to the reactivity of other hydrocarbons. Reactivity can be determined by comparing the influence that different hydrocarbons have on the oxidation rate of nitric oxide (NO) to nitrogen dioxide (NO ), or the relative degradation rate of various 2 hydrocarbons when reacted with hydroxyl radicals (OH), atomic oxygen or ozone. For example, based on the NO oxidation test, the photochemical reactivity rate of benzene was determined to be one-tenth that of propylene and one-third that of n-hexane.9 Benzene shows long-term stability in the atmosphere.8 Oxidation of benzene will occur only under extreme conditions involving a catalyst or elevated temperature or pressure. Photolysis is possible only in the presence of sensitizers and is dependent on wavelength absorption. Benzene does not absorb wavelengths longer than 1.1x10-5 inches (in) (275 nanometers [nm]).8 In laboratory evaluation, benzene is predicted to form phenols and ring cleavage products when reacted with OH, and to form quinone and ring cleavage products when reacted with aromatic hydrogen.6 Other products that are predicted to form from indirect reactions with benzene in the atmosphere include aldehydes, peroxides, and epoxides. Photodegradation of NO produces atomic oxygen, which can react with atmospheric benzene to form phenols.