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A phenol the coefficient is defined as
A Ratio of concentration of disinfectants to that of concentration of phenol
B. Ratio of concentration of phenol to that of concentration of disinfectants
C. Ratio of concentration of antibiotics to that concentration of disinfectants
D. Ratio of concentration of antibodies to that concentration of disinfectants

Last updated date: 13th Jun 2024
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Hint: Phenol is an aromatic compound and potent disinfectant. phenol is disinfectant which helps in specifying the germicidal strength of another disinfectant. It helps in determining the effectiveness of disinfectant.

Complete Answer:
Option A: Ratio of the concentration of disinfectants to that of concentration of phenol is incorrect.

Option B: Phenol coefficient is a number associated with bactericidal efficiency of a compound to phenol. Phenol coefficient is calculated by dividing the concentration of test disinfectant by dilution of phenol that kills microorganisms in 10 minutes under predetermined conditions.
- A phenol coefficient greater than one indicates that the test disinfectant is stronger than phenol whereas phenol coefficient but one indicates that disinfectant is a smaller amount efficient than phenol.
It is determined by two methods:
1. Rideal Walker method but oftenly high values of coefficient are seen with unrealistic conditions.
2. The Chick Martin test used more realistic conditions but replaced by adequate methods, Staphylococcus aureus and Salmonella typhi are used for testing. Dilution of phenol and rest compounds are inoculated with them and incubated at 20-37°C for 2-3 days.

Hence the correct answer is option B.

Note: Disinfectant is substances used to destroy microorganisms and inert surfaces. Testing of disinfectant is useful in identifying efficacy. Phenol coefficient was a commonly used method but it is no longer used.