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Octanol-Water Partition Coefficient (KOW)


Octanol-Water Partition Coefficient (KOW) - "An organic compound's octanol-water partition coefficient, KOW, is defined as the ratio of the compound's concentration in a known volume of n-octanol to its concentration in a known volume of water after the octanol and water have reached equilibrium ... Water solubility was found to be the major factor affecting the partition coefficient." - Smith and others, 1988

Octanol-Water Partition Coefficient (KOW) - "The octanol-water partition coefficient is a dimensionless concentration ratio whose magnitude expresses the distribution of a compound between equal volumes of two partially miscible solvents, n-octanol and water." - Witkowski and others, 1987

Octanol-Water Partition Coefficient (KOW) - "The octanol/water partition coefficient (KOW) is defined as the ratio of a chemical's concentration in the octanol phase to its concentration in the aqueous phase of a two-phase octanol/water system ... Numerous studies showed that KOW was useful for correlating structural changes of drug chemicals with the change observed in some biological, biochemical, or toxic effect ... It has been found to be related to water solubility, soil/sediment adsorption coefficients, and bioconcentration factors for aquatic life." - Lyman and others, 1990

Octanol-Water Partition Coefficient (KOW) - "The octanol-water partition coefficient (KOW) is defined as the ratio of the concentration of a chemical in n-octanol and water at equilibrium at a specified temperature. It is assumed that the molecular speciation of the solute is the same in both solvents and that the solutions are sufficiently dilute." - Pontolillo and Eganhouse, 2001

Octanol-Water Partition Coefficient (KOW) - "A coefficient representing the ratio of the solubility of a compound in octanol (a non-polar solvent) to its solubility in water (a polar solvent). The higher to KOW, the more non-polar the compound. Log KOW is generally used as a relative indicator of the tendency of an organic compound to adsorb to soil. Log KOW values are generally inversely related to aqueous solubility and directly proportional to molecular weight." - U.S. Environmental Protection Agency, 2009

Related Definitions

Water Solubility (SW)


USGS Information on KOW

Related Science Feature Articles

More Information on KOW

  • The Kow Controversy, Renner, Rebecca, 2002, Environmental Science and Technology, v. 36, no. 21, p. 411A-413A.


Leo, A., Hansch, C., and Elkins, D., 1971, Partition coefficients and their uses: Chemical Reviews, v. 71, no. 6, p. 525-616.

Lyman, W.J., Reehl, W.F., and Rosenblatt, D.H., 1990, Handbook of chemical property estimation methods--Environmental behavior of organic compounds: Washington, DC, American Chemical Society, 960 p.

Pontolillo, J., and Eganhouse, R.P., 2001, The search for reliable aqueous solubility (SW) and octanol-water partition coefficient (KOW) data for hydrophobic organic compounds--DDT and DDE as a case study: U.S. Geological Survey Water-Resources Investigations 01-4201, 51 p.

Smith, J.A., Witkowski, P.J., and Fusillo, T.V., 1988, Manmade organic compounds in the surface waters of the United States--A review of current understanding: U.S. Geological Survey Circular 1007, 92 p.

U.S. Environmental Protection Agency, 2009, Glossary of technical terms: U.S. Environmental Protection Agency, access date May 24, 2011.

Witkowski, P.J., Smith, J.A., Fusillo, T.V., and Chiou, C.T., 1987, A review of surface-water sediment fractions and their interactions with persistent manmade organic compounds: U.S. Geological Survey Circular 993, 39 p.


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