Tabun

CAS RN:77-81-6

Volatilization

The Henry's Law constant for tabun is estimated as 1.5X10-7 atm-cu m/mole(SRC), derived from its vapor pressure, 0.07 mm Hg(1), and water solubility, 9.8X10+4 mg/L(2). This Henry's Law constant indicates that tabun is expected to be essentially nonvolatile from water surfaces(3). Tabun's estimated Henry's Law constant indicates that volatilization from moist soil surfaces is not expected to occur(SRC). In addition, any volatilization from moist soil would be attenuated by hydrolysis(SRC) since tabun hydrolyzes in water(1). Liquid tabun may persist for 1 to 2 days under average weather conditions and evaporates about 20 times more slowly than water(1). In a Norwegian study, tabun was found to volatilize from snow slowly; tabun was present 2 weeks after being sprayed on snow, but was not measurable after 4 weeks(1). Field studies measuring the evaporation rate of tabun from soil found that 50% of applied tabun evaporated in 1.71 hr and that 90% evaporated in 4.66 hr(4).
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