Note: Acetic acid is an impurity in refined formic acid (≤ 6 wt %) (Arthur and Struthers, 1949) CASRN: 64-18-6; DOT: 1779; DOT label: Corrosive; molecular formula: CH2O2; FW: 46.03; RTECS: LQ4900000; Merck Index: 12, 4268 Physical state, color, and odor: Clear, colorless, fuming liquid with a pungent, penetrating odor. Odor threshold concentration is 49 ppm (quoted, Amoore and Hautala, 1983). Melting point (°C): 8.1 (Barham and Clark, 1951) Boiling point (°C): 100.7 (Dreisbach and Shrader, 1949) Density (g/cm3): 1.2267 at 15 °C (Sax and Lewis, 1987) 1.2200 at 20 °C (Barham and Clark, 1951) 1.21045 at 25 °C (Huntress and Mulliken, 1941) Diffusivity in water (x 10-5 cm2/sec): 1.57 at 20 °C using method of Hayduk and Laudie (1974) Dissociation constant, pKa: 3.75 at 20 °C (Gordon and Ford, 1972) Flash point (°C): 50 (99% solution, BASF, 1997c) 69 (open cup, Hawley, 1981) Lower explosive limit (%): 18 (90% solution, NIOSH, 1997) Upper explosive limit (%): 57 (90% solution, NIOSH, 1997) Heat of fusion (kcal/mol): 3.035 (Dean, 1987) Henry’s law constant (x 10-7 atm⋅m3/mol): 1.12 at 25 °C (Johnson et al., 1996) 1.81 at the pH range 1.6 to 1.9 (Khan and Brimblecombe, 1992; Khan et al., 1995) 0.77 at 25 °C (value concentration dependent, Servant et al., 1991)
respectively (Hakuta et al., 1977)
Ionization potential (eV): 11.05 ± 0.01 (Franklin et al., 1969) 11.33 (Gibson et al., 1977) Soil organic carbon/water partition coefficient, log Koc: Unavailable because experimental methods for estimation of this parameter for aliphatic carboxylic acids are lacking in the documented literature. However, its high solubility in water suggests its adsorption to soil will be nominal (Lyman et al., 1982). Octanol/water partition coefficient, log Kow: -0.53 at 20.0 °C (shake flask-titrimetry, Collander, 1951) Solubility in organics: Soluble in acetone, benzene (Weast, 1986); miscible with alcohol, ether, and glycerol (Windholz et al., 1983). Solubility in water: Miscible (Price et al., 1974) Vapor density: 1.88 g/L at 25 °C, 1.59 (air = 1) Vapor pressure (mmHg): 35 at 20 °C, 54 at 30 °C (quoted, Verschueren, 1983) 42.6 at 25 °C (Banerjee et al., 1990) Environmental fate: Biological. Near Wilmington, NC, organic wastes containing formic acid (representing 11.4% of total dissolved organic carbon) were injected into an aquifer containing saline water to a depth of about 1,000 feet. The generation of gaseous components (hydrogen, nitrogen, hydrogen sulfide, carbon dioxide, and methane) suggested that formic acid and possibly other waste constituents were anaerobically degraded by microorganisms (Leenheer et al., 1976). Heukelekian and Rand (1955) reported a 5-d BOD value of 0.20 g/g which is 57.1% of the ThOD value of 0.83 g/g. Photolytic. Experimentally determined rate constants for the reaction of formic acid with OH radicals in the atmosphere and aqueous solution were 3.7 x 10-13 and 2.2 x 10-13 cm3/molecule⋅sec, respectively (Dagaut et al., 1988). Chemical/Physical. Slowly decomposes to carbon monoxide and water. At 20 °C, 0.06 g of water would form in 1 yr by 122 g formic acid. At standard temperature and pressure, this amount of formic acid would produce carbon monoxide at a rate of 0.15 mL/h. The rate of decomposition decreases with time because the water produced acts as a negative catalyst (Barham and Clark, 1951). Slowly reacts with alcohols and anhydrides forming formate esters. At an influent concentration of 1.00 g/L, treatment with GAC resulted in an effluent concentration of 765 mg/L. The adsorbability of the GAC used was 47 mg/g carbon (Guisti et al., 1974). Exposure limits: NIOSH REL: TWA 5 ppm (9 mg/m3), IDLH 30 ppm; OSHA PEL: TWA 5 ppm; ACGIH TLA: TWA 5 ppm, STEL 10 ppm (adopted).