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.
Dorland's Illustrated Medical Dictionary. (2004). Phenol c. Obtained Nov. 6, 2006. Salmonella typhosa is used as test orgnism for this test.