ABSTRACT
I CH3 CASRN: 74-88-4; DOT: 2644; DOT label: Poison; molecular formula: CH3I; FW: 141.94; RTECS: PA9450000; Merck Index: 12, 6161 Physical state and color: Clear, colorless liquid which may become yellow, red, or brown on exposure to light and moisture Melting point (°C): -64.4 (Stull, 1947) Boiling point (°C): 42.4 (Weast, 1986) Density (g/cm3): 2.279 at 20 °C (Weast, 1986) Diffusivity in water (x 10-5 cm2/sec): 1.17 at 20 °C using method of Hayduk and Laudie (1974) Flash point (°C): Noncombustible liquid (NIOSH, 1997). Henry’s law constant (x 10-3 atm⋅m3/mol): 5.87 at 25 °C (quoted, Liss and Slater, 1974) 5.26 at 25 °C (Hunter-Smith et al., 1983) 5.08 at 25 °C (Glowa and Wren, 2003) In seawater (salinity 30.4‰): 1.71 at 0 °C, 3.16 at 10 °C, 5.40 at 20 °C (Moore et al., 1995) 5.06 at 21 °C (Gan and Yates, 1996) Ionization potential (eV): 9.54 (Franklin et al., 1969) 9.86 (Gibson et al., 1977) Soil organic carbon/water partition coefficient, log Koc: 1.23 (Greenfield sandy loam), 1.04 (Carsetas loamy sand), 0.94 (Linne clay loam) (Gan and Yates, 1996) Octanol/water partition coefficient, log Kow: 1.69 at 19 °C (shake flask-titration, Collander, 1951) 1.51 (Hansch et al., 1975; Hansch and Leo, 1979) Solubility in organics: Soluble in acetone and benzene (Weast, 1986). Miscible with alcohol and ether (Windholz et al., 1983). Solubility in water: In g/kg H2O: 15.65 at 0 °C, 14.46 at 10 °C, 14.19 at 20 °C, 14.29 at 30 °C (Rex, 1906)
95.9 mM at 22 °C (shake flask-turbidimetric, Fühner, 1924) Vapor density: 5.80 g/L at 25 °C, 4.90 (air = 1) Vapor pressure (mmHg): 331 at 20 °C, 483 at 30 °C (Rex, 1906) 405 at 25 °C (calculated, Kudchadker et al., 1979) Environmental fate: Chemical/Physical. Anticipated products from the reaction of methyl iodide with ozone or OH radicals in the atmosphere are formaldehyde, iodoformaldehyde, carbon monoxide, and iodine radicals (Cupitt, 1980). With OH radicals, CH2, methyl radical, HOI and water are possible reaction products (Brown et al., 1990). The estimated half-life of methyl iodide in the atmosphere, based on a measured rate constant for the vapor phase reaction with OH radicals, ranges from 535 h to 32 wk (Garraway and Donovan, 1979). Hydrolyzes in water forming methyl alcohol and hydriodic acid. The estimated half-life in water at 25 °C and pH 7 is 110 d (Mabey and Mill, 1978). At 70 °C, the hydrolysis rate was determined to be 3.2 x 10-5/sec which is equivalent to a half-life of 6 h. (Glows and Wren, 2003). May react with chlorides in seawater to form methyl chloride (Zafiriou, 1975). Exposure limits: Potential occupational carcinogen. NIOSH REL: TWA 2 ppm (10 mg/m3), IDLH 100 ppm; OSHA PEL: TWA 5 ppm (28 mg/m3); ACGIH TLV: TWA 2 ppm (adopted). Symptoms of exposure: An irritation concentration of 21.50 g/m3 in air was reported by Ruth (1986). Toxicity: LD50 (intraperitoneal) for guinea pigs 51 mg/kg, mice 172 mg/kg, rats 101 mg/kg (quoted, RTECS, 1985). LD50 (subcutaneous) for mice 110 mg/kg (quoted, RTECS, 1985). Uses: Microscopy; medicine; testing for pyridine; methylating agent.
