Note: Formaldehyde solutions usually contain methanol as a stabilizer to inhibit polymerization. CASRN: 50-00-0; DOT: 1198, 2209; DOT label: Combustible liquid (aqueous solutions); molecular formula: CH2O; FW: 30.03; RTECS: LP8925000; Merck Index: 12, 4262 Physical state, color, odor, and taste: Clear, colorless liquid with a pungent, suffocating odor. Burning taste. Experimentally determined odor threshold concentrations of 1.0 ppmv and 0.50 ppmv were reported by Leonardos et al. (1969) and Nagata and Takeuchi (1990), respectively. Melting point (°C): -92 (Weast, 1986) Boiling point (°C): -21 (Weast, 1986) Density (g/cm3): 0.815 at -20 °C (Windholz et al., 1983) Flash point (°C): 50 (37% aqueous solution, NFPA, 1984) Lower explosive limit (%): 7.0 (NIOSH, 1997) Upper explosive limit (%): 73 (NIOSH, 1997) Henry’s law constant (x 10-7 atm⋅m3/mol): 1.01 at 10 °C, 2.95 at 25 °C, 5.00 at 30 °C, 6.67 at 35 °C, 9.09 at 40 °C, 12.3 at 45 °C (bubble
column-HPLC, Zhou and Mopper, 1990) 1.37 at 15 °C, 3.37 at 25 °C, 6.67 at 35 °C, 14.9 at 45 °C (bubble column-spectrofluorometry,
Betterton and Hoffmann, 1988) 0.518 at 5 °C, 0.721 at 10 °C, 0.892 at 15 °C, 1.699 at 20 °C, 2.658 at 25 °C (bubble column,
Anthon et al., 1986) 2.08 at 25 °C (flow-type generation system, spectrophometry, Kanda et al., 2005) Ionization potential (eV): 10.88 (Franklin et al., 1969) Soil organic carbon/water partition coefficient, log Koc: 0.56 (calculated, Mercer et al., 1990)
ow 0.35 at 25.0 °C (shake flask-chemical reaction, Johnson and Piret, 1948) Solubility in organics: Soluble in acetone, benzene, ether (Weast, 1986), and ethanol (Worthing and Hance, 1991) Solubility in water: 461.0 g/kg at 27.46 °C (thin-film evaporator-titration, Grützner and Hasse, 2004) Vapor density: 1.067 (air = 1) (Windholz et al., 1983) 1.23 g/L at 25 °C Vapor pressure (mmHg): 3,900 at 25 °C (Lide, 1990) Environmental fate: Biological. Biodegradation products reported include formic acid and ethanol, each of which can degrade to carbon dioxide (quoted, Verschueren, 1983). Heukelekian and Rand (1955) reported a 5-d BOD value of 0.74 g/g which is 69.4% of the ThOD value of 1.07 g/g. Photolytic. Major products reported from the photooxidation of formaldehyde with nitrogen oxides are carbon monoxide, carbon dioxide, and hydrogen peroxide (Altshuller, 1983). In synthetic air, photolysis of formaldehyde yields hydrogen chloride, and carbon monoxide (Su et al., 1979). Calvert et al. (1972) reported, however, that formaldehyde photodecomposed by direct sunlight in the atmosphere yielding hydrogen, formyl radicals, and carbon monoxide. Photooxidation of formaldehyde in nitrogen oxide-free air using radiation between 2900 and 3500 Å yielded hydrogen peroxide, alkylhydroperoxides, carbon monoxide, and lower molecular weight aldehydes. In the presence of NOx, photooxidation products reported include ozone, hydrogen peroxide, and peroxyacyl nitrates (Kopczynski et al., 1974). Rate constants reported for the reaction of formaldehyde and OH radicals in the atmosphere include 9.0 x 10-12 cm3/molecule⋅sec at 300 K (Hendry and Kenley, 1979), 1.4 x 10-11 cm3/molecule⋅sec (Morris and Niki, 1971), 1.5 x 10-11 cm3/molecule⋅sec (Niki et al., 1978), 1.11 x 10-13 cm3/molecule⋅sec at 298 K (Baulch et al., 1984). Irradiation of gaseous formaldehyde containing an excess of nitrogen dioxide over chlorine yielded ozone, carbon monoxide, nitrogen pentoxide, nitryl chloride, nitric and hydrochloric acids. Peroxynitric acid was the major photolysis product when chlorine concentration exceeded the nitrogen dioxide concentration (Hanst and Gay, 1977). Formaldehyde also reacts with NO3 in the atmosphere at a rate of 3.2 x 10-16 cm3/molecule·sec (Atkinson and Lloyd, 1984). Chemical/Physical. Oxidizes in air to formic acid. Trioxymethylene (polymerization product) may precipitate under cold temperatures (Sax, 1984). Polymerizes easily (Windholz et al., 1983) and is a strong reducing agent (Worthing and Hance, 1991). Anticipated products from the reaction of formaldehyde with ozone or OH radicals in the atmosphere are carbon monoxide and carbon dioxide (Cupitt, 1980). Major products reported from the photooxidation of formaldehyde with nitrogen oxides are carbon monoxide, carbon dioxide, and hydrogen peroxide (Altshuller, 1983). Formaldehyde reacted with hydrogen chloride in moist air to form sym-dichloromethyl ether. This compound may also form from an acidic solution containing chloride ions and formaldehyde (Frankel et al., 1974; Travenius, 1982). In an aqueous solution at 25 °C, nearly all the formaldehyde added is hydrated forming a gem-diol (Bell and McDougall, 1960). May polymerize in an aqueous solution to trioxymethylene (Hartley and Kidd, 1987).