86 BIOLOGY AND TECHNIQUE 



Lbs. Pressure Temperature j Lbs. Pressure Temperature 



1 102.3C. I 13 119.10. 



. 104.2 14 . . 120.2 



3 105.7 



4 107.3 



5 108.8 



6 110.3 



7 111.7 



8 113 



9 114.3 ( 



10 115.6 



11 116.8 



12 . . 118 



15 121.3 



16 122.4 



17 123.3 



18 124.3 



20 126.2 



22 128.1 



24 129.3 



26 131.5 



28 133.1 



30 . . 134.6 



CHEMICAL AGENTS INJURIOUS TO BACTERIA 



Since the time of Koch's 32 fundamental researches upon chemical 

 disinfectants, the known number of these substances has been 

 enormously increased, and now embraces chemical agents of the 

 most varied constitution. It is thus manifestly impossible to refer 

 the injurious influence which these substances exert upon bacteria 

 to any uniform law of action. The efficiency of a disinfecting agent, 

 furthermore, is not alone dependent upon the nature and concen- 

 trations of the substance itself, but depends complexly upon the 

 nature of the solvent in which it is employed, the temperature pre- 

 vailing during its application, the numbers and biological character- 

 istics of the bacteria in question, and the time of exposure. All 

 these factors, therefore, must be considered in testing the efficiency 

 of any given disinfectant. While it is true, furthermore, that all 

 substances which in a given concentration exert bactericidal or 

 disinfecting action upon a microorganism, will in greater dilution 

 act antiseptically or inhibitively, no definite rules of proportion exist 

 between the two values, which in each case must be determined 

 by experiment. 



Disinfectants Used in Solution. The actual processes which take 

 place in the injury of bacteria by disinfectants are to a large extent 

 unknown. In the ease of strong acids, or strongly oxidizing sub- 

 Stances, there may be destruction of the bacterial body as a whole 

 by rapid oxidation. Other substances may act by coagulation of 

 the bacterial protoplasm; others again by diffusion through the 

 cell membrane are able to enter into chemical combination with the 



82 Koch, Arb. a. d. kais. Gesundheitsamt, i, 1881. 



