Chlorine

CAS RN: 7782-50-5

Volatilization

The Henry's Law constant for chlorine is 0.0104 atm-cu m/mole(1). This Henry's Law constant indicates that chlorine is expected to volatilize rapidly from water surfaces(2). 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)(2) is estimated as 2.5 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)(2) is estimated as 3.4 days(SRC). However, chlorine hydrolyzes rapidly and almost completely in water to form hydrochloric acid, hypochlorous acid, and hypochlorite with the speciation dependent on pH(3). Free chlorine exists at pHs below 4.5; percent increases as the pH decreases below pH 4.5(3). At environmental pHs of 5-9, the percent of free chlorine is nearly zero(3) which would minimize volatilization from water(SRC). Chlorine's Henry's Law constant indicates that volatilization from moist soil surfaces may occur assuming free chlorine exists(SRC). Chlorine is a gas with a vapor pressure of 5850 mm Hg at 25 deg C and atmospheric pressure(4), and therefore, is expected to volatilize from dry soil surfaces(SRC).
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