Disinfectants concentration exponent

Table 11.1 Concentration exponents, 77, for some disinfectant substances...

Mercuric chloride has a concentration exponent of 1 thus, the activity will be reduced by the power of 1 on dilution, and a threefold dilution means the disinfectant activity will be reduced by the value 3 or 3, that is to a third. Put another way the disinfection time will be three times as long. In the case of phenol, however, with a concentration exponent of 6, a threefold dilution will mean a decrease in activity of 3 = 729, a figure 243 times the value for mercuric chloride. This explains why phenols may be rapidly inactivated by dilution and should sound a warning bell regarding claims for diluted phenol solutions based on data obtained at high concentrations. 

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