Final answer:
The statement is false; efficient disinfectant action typically relies more on the availability of free residual chlorine than combined residual chlorine, as free chlorine is ready to actively disinfect whereas combined chlorine is less effective for this purpose.
Step-by-step explanation:
The assertion that for efficient disinfectant action, a greater concentration of combined residual chlorine than free residual chlorine is required is false. Free chlorine residual comprises chlorine in forms ready for disinfection, like Cl2, HOCl, and OCl−, whereas combined chlorine residual refers to chlorine in its reduced form, like NH2Cl, NHCl2, and NCl3, which are not effective in disinfecting. Effective disinfection typically relies primarily on free residual chlorine because it actively destroys pathogens. Combined chlorine, while present, is less effective as it has reacted with other compounds and is in a form that does not significantly contribute to disinfectant action.
Considering the efficiency of disinfectants also involves evaluating factors such as the susceptibility of the pathogen, the intensity of exposure, and conditions that may limit the contact between the disinfectant and microorganisms. For example, the presence of organic matter can reduce the effectiveness of chlorine. Additionally, experiments have shown that ensuring lethal effects can be achieved with the lowest possible concentration of chlorine to avoid disadvantages like irritation to skin or incompletely eliminating certain organisms, which is always a balance of efficacy and safety.
The Use-Dilution Test is a method that helps to determine the correct usage and effectiveness of disinfectants on surfaces in clinical settings. It involves exposing a stainless steel cylinder coated with the targeted microorganisms to different concentrations of disinfectants to observe whether the bacteria survive or are killed by the treatment.