198 MANUAL OF BACTERIOLOGY. 



Chemical Disinfection.* 



Heat properly applied is the simplest and at the same time 

 the surest disinfectant (see Part I., Chapter II.); but for many 

 purposes it cannot be used, and we have recourse to those 

 chemicals that practice and investigation have shown to be 

 of value. The efficiency of chemical disinfectants as ordinarily 

 used is overrated. An immense number of substances possess 

 germicidal properties, but, unfortunately, the majority are objec- 

 tionable in that they are expensive, intensely poisonous, or so 

 corrosive that damage may be done to articles of value with 

 which they may come in contact. 



In the following pages only those substances which are in 

 common use or seem to be of special value will be considered. 



Mercuric Chloride or Corrosive Sublimate. — This substance 

 is probably more commonly used than any other one germicide. 

 In the strength of i-iooo it will sometimes kill the spores of an- 

 thrax within a few minutes (see Bacillus anthracis. Part IV.). 

 It is claimed that its afhnity for albuminous bodies and the 

 readiness with which it combines with such substances de- 

 tract from its value for some purposes. On the other hand, 

 many observers claim that the albuminous combinations 

 formed under such circumstances are soluble in an excess of 

 albuminous fluid, and that its value as a germicide is not affected 

 thereby. To obviate this possible difficulty it is customary in 

 practice to combine the bichloride of mercury with some sub- 

 stance that will prevent the precipitation of the mercury salt 

 by albumin. For this purpose 5 parts of any one of the fol- 

 lowing substances to i part of bichloride of mercury may be 

 used — hydrochloric acid, tartaric acid, sodium chloride, potas- 



* For fuller details on this subject consult Rosenau. Disinfection and Dis- 

 infectants. 1902. 



