Rideal–Walker coefficient

Rideal–Walker coefficient is a numerical value that represents the disinfecting power of a chemical agent in comparison to phenol. It was developed by English chemists Samuel Rideal and J.T.A. Walker in 1903. The coefficient is determined by comparing the dilution of the test disinfectant that kills a specific test organism in a specified time with the dilution of phenol that kills the same organism under the same conditions.

History

The Rideal–Walker test was developed in the early 20th century as a method for comparing the effectiveness of disinfectants. The test was named after its creators, Samuel Rideal and J.T.A. Walker, who were both prominent chemists in England at the time. The test was widely used in the field of microbiology and public health for many years, although it has since been largely replaced by more modern methods.

Calculation

The Rideal–Walker coefficient is calculated by dividing the dilution of the test disinfectant that kills a specific test organism in a specified time by the dilution of phenol that kills the same organism under the same conditions. The resulting number is the Rideal–Walker coefficient. A coefficient of 1 indicates that the disinfectant is as effective as phenol, while a coefficient greater than 1 indicates that the disinfectant is more effective than phenol.

Limitations

While the Rideal–Walker coefficient provides a useful measure of the relative effectiveness of different disinfectants, it has several limitations. The test is highly dependent on the specific test organism and the conditions under which the test is conducted. Furthermore, the test does not take into account the effect of organic matter on the effectiveness of the disinfectant, which can be a significant factor in real-world applications.

See also

• Chick–Martin test
• Phenol coefficient
• Disinfectants
• Antiseptics

External links

• Britannica Online Encyclopedia: Rideal-Walker coefficient