Phenol coefficient indicates: (A) Efficacy of a disinfectant, (B) Dilution of a disinfectant, (C) Quantity of a disinfectant, (D) Purity of a disinfectant
Answer is A. On exposure to air, the colorless crystals of phenol become pinkish and on longer exposure, the color deepens to dark blue. Pure phenol is not an effective disinfectant. It is used as an effective disinfectant. Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 140