Lewisite

CAS RN: 541-25-3

Volatilization

The Henry's Law constant for Lewisite is estimated as 3.2X10-4 atm-cu m/mole(SRC), derived from its vapor pressure, 0.58 mm Hg(1), and water solubility, 500 mg/L(2). This Henry's Law constant indicates that lewisite is expected to volatilize from water surfaces(3). Based on this Henry's Law constant, the volatilization half-life from a model river (1 m deep, flowing 1 m/sec, wind velocity of 3 m/sec)(3) is estimated as 10 hours(SRC). The volatilization half-life from a model lake (1 m deep, flowing 0.05 m/sec, wind velocity of 0.5 m/sec)(3) is estimated as 7 days(SRC). Lewisite's estimated Henry's Law constant indicates that volatilization from moist soil surfaces may occur(SRC). While the Henry's Law constant for Lewisite indicates volatilization from water and moist soil surfaces, the rapid rate of hydrolysis may reduce the importance of this fate pathway(4). Lewisite is rapidly hydrolyzed by soil moisture, and minerals present in the soil would speed the process(5). Lewisite may volatilize slowly from dry soil surfaces(SRC) based upon its vapor pressure(1). When Lewisite was placed on soil at 51 deg C, 20% evaporated in the first hour and none thereafter(6); the cessation of evaporation was thought to be the result of hydrolysis conversion to lewisite oxide which is nonvolatile(6).
Find more information on this substance at: PubChem, PubMed