74 DISINFECTANTS 



There is still more inconsistency with disinfectants 

 which combine readily with various kinds of organic 

 matter. A typical example is that of the concentration 

 exponent of mercuric chloride which was found to have 

 the following values in various cases : 



0.25 Alfred Miiller, 1920, with anthrax spores; 

 0.5 Gegenbauer, 1921, with Staph, aureus; 



3.8 Chick, 1908, with Bact. typhosum; 



4.9 Chick, 1908, with anthrax spores. 



It seems c( rtain that, with this compound, different 

 amounts of organic matter in the test solution are re- 

 sponsible for different values of n. If in one case the 

 proteins of the medium precipitate 90% of the HgCL 

 present, while in another they precipitate 10%, the values 

 of the concentration coefficient must necessarily be very 

 different. 



Another unsettled point is the degree of specificity of 

 the organisms. Different bacteria might give different 

 concentration exponents with the same disinfectant. The 

 only systematic research known to the author on this 

 subject is that cited in the middle section of Table 15. 

 There are differences between the exponents obtained with 

 Bact. typhosum and Staph, aureus, but they are not con- 

 sistent. 



III. TEMPERATURE AND DISINFECTION 



The preceding chapter bears out the general assump- 

 tion that disinfection is the result of a chemical reaction 

 of measurable velocity. Such reactions are usually af- 

 fected by changes in temperature. The rate of most 

 chemical reactions increases when the temperature rises, 

 and so does the death rate. The increase in rate differs 

 with, the type of chemical reaction, and a quantitative de- 

 termination of the effect of temperature on disinfection 

 is therefore important in the search for the "lethal 



