Henry's Law

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Henry's Law Constant-The air to water partition coefficient that is expressed as ratio of vapor pressure to water solubility or as a unitless distribution coefficient that can be evaluated as a ratio of the concentration in air to the concentration in water.

Two methods are used to predict Henry's Law constant.

1. The first is an approach based on the bond contribution method. This method uses 59 bond contribution values and 15 correction factors. The contributions were calculated by least squares analysis using a data set of 345 chemicals. This method estimates with a mean error of 0.30 units and a standard deviation of 0.45 units and can handle molecules containing carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus and halogens.

2. In the second method, Henry's Law constant is estimated from an equation found using linear regression. Multifunctional compounds were omitted from this study. This method should not be used for compounds where distant polar interaction is present.