344 PHYSIOLOGY OF BACTERIA 



action is fairly alike, and equal that of an n/8 di- 

 chloracetic acid which has the same hydrogen ion 

 concentration. 



This table shows also that the anions of hydrofluoric 

 acid, nitric acid and trichloracetic acid have a specific 

 toxic action, which becomes less conspicuous upon 

 dilution as compared with the hydrogen ion effect. 



Further experiments indicate that the alkalies dis- 

 infect in proportion to their hydroxyl ions. A compari- 

 son of the data shows that the hydroxyl ions do not 

 act as strongly as the hydrogen ions; this is especially 

 true for Micrococci. 



The same authors (Kronig and Paul) studied, further, 

 the effect of oxidants such as chlorine, bromine, iodine, 

 permanganate, chlorate, bichromate, persulfate, and 

 hydrogen peroxide, also of organic disinfectants like 

 phenol and its derivatives. The effect of alcohol upon 

 the disinfectant value has been studied quite extensively. 

 It is not the object of this book to go into these details. 

 Kronig and Paul's paper, now over 30 years old, started 

 a new era in disinfection experiments, and is still a 

 model of carefully planned and executed technique. It 

 was the necessary prerequisite for the discovery of the 

 logarithmic order of death which followed ten years later. 



After this discovery, various disinfectants were tried 

 on a number of microorganisms in a quantitative way, 

 but the test organisms in all these experiments were 

 limited to a few species, and the kinds of disinfectants 

 used also were few. The final outcome of all these 

 investigations, which were very numerous in the years 

 1908-1912, has not fulfilled the expectations; they have 

 had very little influence upon practical disinfection. 



The main reason for this lies in the fact that ordinarily, no result 

 can be duplicated exactly, not even by the same author. While we 



