IX. 



ACTION OF ACIDS AND ALKALIES. 



Sulphuric Acid, H 2 SO 4 . The experiments of Koch (1881) 

 showed that anthrax spores were still capable of growing after ex- 

 posure in a one-per-cent solution of sulphuric acid for twenty days. 

 In the writer's experiments (1885) a four-per-cent solution failed to 

 destroy the spores of Bacillus subtilis in four hours, and an eight- 

 per-cent solution was found to be required for the sterilization of 

 culture fluids containing spores ; but the multiplication of the bacte- 

 ria of putrefaction was prevented by the presence of this acid in a 

 culture solution in the proportion of 1 : 800. Pus micrococci were 

 destroyed by exposure for two hours in a solution containing 1 : 200. 



The experiments of Boer show that there is a considerable differ- 

 ence in the resisting power of different pathogenic bacteria. The 

 time of exposure being two hours, cultures in bouillon twenty-four 

 hours old gave the following results : 



Leitz, in his studies relating to the bacillus of typhoid fever, 

 reports the following results : The dejections of typhoid patients, 

 mixed with an equal proportion of the disinfecting solution, were 

 sterilized by a five-per-cent solution of sulphuric acid in three days. 

 A pure culture was sterilized in fifteen minutes by two per cent, and 

 in five minutes by five per cent. 



Sulphurous Acid, H 2 SO 3 . In the writer's experiments (1885) 

 micrococci were destroyed in two hours by 1 : 2,000 by weight of SO, 

 added to water. Kitasato found that solutions of sulphurous acid 

 in the proportion of 0.28 per cent killed the typhoid bacillus, and 

 0. 148 per cent the cholera spirillum. De la Croix found that one 



