Studies in the dynamics of disinfection: III. The reaction between phenol andBact. coli: the effect of temperature and concentration: with a detailed analysis of the reaction velocity

Abstract

1. Details are given of further experiments on the disinfection of Bact. coli cultures by phenol using an improved standardized technique. These were carried out at several temperatures at each of five phenol concentrations.2. An excess of high values of χ2 was again observed at high mortalities. Reasons for the occurrence of this phenomenon are discussed.3. The logarithmic death-rates calculated between successive determinations of the surviving cells have been combined and analysed. Strong evidence was obtained that the death-rate rises to a maximum and then falls, sharply at first and then more slowly. There was some evidence for an initial rush in the death-rate.4. The method hitherto adopted for treating these data, based on the assumption that the death-rate rises to a maximum at which it remains constant, has been shown to be a fair approximation but one which leads to low values for the v.s.t.'s.5. Calculated estimates nearer to the true values for the v.s.t.'s have been obtained by treating the last phase of slow decline as one of constant death-rate. All values except those exceeding 1000 min. are increased by this change in method of calculation.6. The new v.s.t.'s do not alter significantly the value previously obtained for the concentration exponent for phenol at 35°C.