Phenol coefficient

Phenol coefficient is a measure of the bactericidal activity of a chemical compound in relation to phenol. When listed numerically, the figure expressing the disinfecting power of a substance by relating it to the disinfecting power of phenol may be a function of the standardized test performed. For example, the Rideal-Walker method gives a Rideal-Walker coefficient and the U.S. Department of Agriculture method gives a U.S. Department of Agriculture coefficient.

To calculate phenol coefficient, the concentration of the test compound at which the compound kills the test organism in 10 minutes, but not in 5 minutes, is divided by the concentration of phenol that kills the organism under the same conditions. The phenol coefficient may be determined in the presence of a standard amount of added organic matter or in the absence of organic matter.