STERILISATION 93 



throat, and causes the eyes to .smart. But its penetrating power is 

 greater than that of most disinfectants. Delepine proved that formalin 

 was fatal to Bac. tuberculosis, Bac. pyocyaneus, and Staphylococcus 

 pyogenes aureus, even when these organisms were protected by three 

 layers of filter paper. 



Mercuric Chloride (corrosive sublimate). This antiseptic is so efficient 

 that 1 in 14,300 is sufficient to sterilise most substances. In the fer- 

 mentation industries its use is out of the question owing to its 

 intensely poisonous properties, but in the laboratory it is invaluable 

 for washing wounds, disinfecting bandages, etc. Glass ware and 

 cultures of bacteria that have been put aside may also be treated with 

 this powerful germicide ; but care should be taken that glass utensils 

 thus treated are thoroughly cleansed from the chloride ; especially is 

 this necessary with tubes that may again be required for bacterial 

 cultures. The strength which is recommended is 1 gram per 1 litre 

 of water. The water must not contain any calcareous matter, and it 

 is also advisable to add 5 grams of common salt per 1 litre of disin- 

 fectant to prevent the corrosive sublimate from forming insoluble 

 compounds with albuminoids, and so prevent its action as a disinfectant. 

 Many experiments have been made to demonstrate the efficiency of 

 this compound. Bac. typhosus and the cholera spirillum, growing in 

 flesh-peptone-gelatine are destroyed in 2 hours by a solution of 1 : 10,000. 

 The anthrax bacillus can be killed by a 1 : 100,000 solution at 36 C., 

 but if the temperature be lowered to 3 C., a 1 : 25,000 solution is 

 required. In experiments upon tuberculous sputum, when fresh, a 

 solution of 1 : 2000 acting for 24 hours, failed to kill the contained 

 bacteria, but a 1 : 1000 solution succeeded after 1 minute. 



Sulphurous Acid. The practice of burning sulphur as a means of 

 disinfection has been known probably as long as the art of making 

 wine. The burning of sulphur produces sulphur dioxide, and when 

 the latter is dissolved in water, sulphurous acid is produced. The 

 cheapness of this method, and the ease with which it can be carried 

 out, has made it very popular for purposes of disinfecting utensils, 

 clothing, etc. ; but, according to the most recent investigations, its 

 disinfecting power is not very great. Sulphur fumes have little or 

 no effect on most bacteria when in a dried state, but when in a 

 moist condition, if they have not formed spores, they can be destroyed 

 by such means. There is one exception, however, viz., the tubercle 

 bacillus ; this organism, though it does not form spores, is very 

 resistant, and, if its presence is suspected, sulphur fumes should not be 

 used. Three to six pounds of sulphur are generally used for every 



