DISINFECTANTS. ANTISEPTICS 179 



Iodoform undergoes a peculiar decomposition when it comes in 

 contact with pus; iodine is set free, and this free iodine is the cause 

 of the antiseptic action of iodoform. 



In the disinfection of stables, many forms of decomposition 

 occur. This is especially the case with corrosive sublimate when 

 it comes in contact with organic or albuminous substances, excre- 

 ment, urine, and water. The disinfection of dried infectious 

 material is particularly difficult; a detailed discussion of this 

 point will be found in a succeeding section. The effective dis- 

 infection of infected dung and liquid manure is very difficult 

 because the organic constituents and' gases (H2S, NH3) decom- 

 pose some antiseptics; e.g., corrosive sublimate. Other disinfec- 

 tants quickly lose their effect because they form ineffective com- 

 binations (change of caustic lime to acid phosphates, silver nitrate 

 to silver chloride, salicylic acid to sodium salicylate). 



Continuance of the Action of Disinfectants. — The rapidity of 

 its disinfectant action is of essential importance in considering 

 the value of any antiseptic. The shorter the action, the stronger 

 usually must be the concentration. It is desirable in practice to 

 continue the action of a quickly acting disinfectant as long as 

 possible upon the object to be disinfected. Antiseptic irrigations 

 of old wounds especially must be continued for a long time (for 

 yi hour and over). Disinfection of stables with autan must 

 continue seven hours. In disinfecting with chlorine and bromine 

 a 24-hour action is necessary. 



In general, a good disinfectant should destroy the bacteria 

 acted upon within a few minutes. This standard cannot be 

 complied with absolutely, particularly not in connection with the 

 spore-containing bacteria, which always require a much longer 

 time for destruction than the spore-free organisms. While carbolic 

 acid, creolin, formaldehyde and corrosive sublimate in suitable 

 concentrations destroy anthrax bacilli at once or at most within 

 a few minutes, they show the following relations to anthrax spores: 



Formaldehyde (2 per cent.) kills anthrax spores after 7 hours. 



Corrosive sublimate (17 per cent.) kills anthrax spores after 

 1 day. 



