ACTION OF ACIDS AND ALKALIES. 177 



gramme of SO 2 added to two thousand of bouillon prevents the de- 

 velopment of putrefactive bacteria and after a time destroys the 

 vitality of these bacteria. The writer found that pus cocci failed to 

 grow in a culture solution containing one part of SO 2 in five thousand 

 of water. 



Nitric Acid, HNO 3 . In the writer's experiments an eight-per- 

 cent solution which contained 0.819 gramme of HNO 3 in each cubic 

 centimetre sterilized broken-down beef tea containing spores, and 

 five per cent failed to do so. Kitasato, in experiments upon the chol- 

 era spirillum and typhoid bacillus, obtained results corresponding 

 with those obtained with hydrochloric acid 0. 2 per cent destroyed 

 vitality at the end of four or five hours. In these experiments the 

 acid used contained 0.35 gramme HNO 3 in one cubic centimetre. 



Nitrous Acid. In the writer's experiments on vaccine virus (1880) 

 exposure for six hours in an atmosphere containing one per cent of 

 nitrous acid destroyed the virulence of dried virus upon ivory points. 



Hydrochloric Acid, HC1. Anthrax spores are destroyed in ten 

 days by a two-per-cent solution, but not in five days (Koch). Tested 

 upon broken-down beef tea containing spores of Bacillus subtilis, it 

 was effective in two hours in the proportion of fifteen per cent, but 

 failed in ten per cent (Sternberg). In the experiments of Kitasato this 

 acid destroyed the typhoid bacillus in five hours in the proportion of 

 0.2 per cent, and the cholera spirillum in 0.132 per cent the acid 

 used contained 0. 26 gramme HC1 in one cubic centimetre. We give 

 the more recent determinations of Boer in tabular form. Its germi- 

 cidal power was tested upon bouillon cultures which had been kept 

 for twenty-four hours in an incubating oven ; time of exposure to 

 the action of the acid solution, two hours. 



Chromic Acid. In Koch's experiments a one-per-cent solution 

 destroyed anthrax spores in from one to two days. In the propor- 

 tion of 1 : 5,000 it prevents the development of putrefactive bacteria 

 (Miquel). 



Osmic Acid. A solution of one per cent kills anthrax spores in 

 twenty-four hours (Koch). It is an antiseptic in the proportion of 

 1 :6,666 (Miquel). 



Phosphoric Acid. Exposure for four or five hours to a solution 

 12 



