Reidel walker test measures efficacy of disinfection by using-

Ans. is 'a' i.e., Phenol coefficient o There is no reliable test available to determine the efficacy of a disinfectant,o This is due to the number of parameters which influence disinfectant activity,o Traditionally in such tests phenol is taken as the standard,o Two important tests areRideal-Walker testSuspensions containing equal numbers of typhoid bacilli are submitted to action of varying concentration of phenol and of the disinfectant to be tested.The dilution of test disinfectant which sterilises the suspension in given time, divided by the corresponding dilution of phenol, is stated as the phenol coefficient of disinfectant (phenol-1).In this test disinfectant react directly without any organic matter being present.Chick-Martin testIn this, the disinfectant acts in the presence of organic matter (dried yeast or feces).