Phenol test or Reidel walker test is done to determine?

TESTING OF DISINFECTANTS There is no single reliable test available to detrmine the efficacy of a disinfectant. This is due to the number of parameters which influence disinfectant activityy. Traditionally in such tests phenol is taken as standard. In Rideal -Walker test, suspension containig equal number of typhoid bacilli are submitted to the action of varying concentration of phenol and of disinfectant to be tested . REF:Ananthanarayan & Panicker's Textbook of Microbiology 8th Edition pg no : 38