STERILIZATION — ANTISEPSIS — FOOD PRESERVATION 75 



cipitate the mercury salt without themselves injuring the bac- 

 teria, growth takes place even where the corrosive sublimate 

 solutions have been used which are apparently efficacious. Thus 

 anthrax spores will not grow in culture media when they are 

 exposed for even a few minutes on silk threads to the action of 

 corrosive sublimate solution of the strength of Ko per cent and 

 then washed thoroughly in water and rinsed in alcohol; but 

 Geppert showed that the spores so treated were only apparently 

 killed, for it took twenty hours' exposure to corrosive sublimate 

 solution of this strength where the spores were not dried on silk 

 threads, but suspended in water, and where the last trace of 

 corrosive sublimate was removed by treatment with ammonium 

 sulphide. It is claimed that its affinity for albuminous bodies 

 and the readiness with which it combines with such substances 

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

 many observers claim that th« 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 substance that will 

 prevent the precipitation of the mercury salt by albumin. For 

 this purpose 5 parts of any one of the following substances to i 

 part of bichloride of mercury may be used — hydrochloric acid, 

 tartaric acid, sodium chloride, potassium chloride, or ammonium 

 chloride. A very practical stock solution for laboratory purposes 

 has the following composition: 



Hydrochloric acid 100 c.c. 



Bichloride of mercury 20 grams. 



Five c.c. in a liter of water makes a solution of about i-iooo strength. 



Mercuric Iodide. — An extremely high antiseptic value has 

 been placed on this substance by Miquel, who claims that the 

 most resistant spores are prevented from developing in a culture 

 medium containing 1-40,000. In combination, as potassio-mer- 

 curic iodide, it has been used in soaps (McClintock) with very 



