96 OUTLINES OF BACTERIOLOGY 



means are discovered to furnish more concentrated solutions of this 

 antiseptic, and other means to prevent its decomposition, which takes 

 place very easily, its use as a practical disinfectant cannot be regarded 

 as satisfactory. Later experiments have shown that Miquel's estimate 

 of 1 : 20,000 is too high, as Altehofer's experiments proved that the 

 ordinary water-bacteria and several of the pathogenic bacteria experi 

 mented upon, required for their destruction an exposure of twenty- 

 four hours in a solution containing hydrogen peroxide, in the pro- 

 portion 1 : 1000. This considerably lowers the value of hydrogen 

 dioxide as a disinfectant. 



Carbonic Acid Gas or Carbon Dioxide. Several experiments have 

 been made to test the value of this gas in preventing the growth of 

 bacteria. In many of them it is impossible to say whether the absence 

 of growth was due to the absence of oxygen, or to the presence of 

 carbon dioxide, but, according to Frankel, a number of anaerobic 

 bacteria were hindered in their growth by the presence of this gas. 

 Again, two species of spirillum failed to develop under the same 

 conditions, and after eight days, when air was again introduced, the 

 two species were no longer capable of growth. In this last experiment 

 the deprival of oxygen for eight days might have been the cause of 

 death. For practical purposes, carbon dioxide is not strong enough to 

 be regarded as an efficient disinfectant. 



Potassium Permanganate. According to Miquel, 1 : 285 is the 

 proportion in which this substance begins to be effective. 



The following results indicate its efficiency : 



1. Pus cocci were killed in two hours by immersion in a 



1 : 833 solution. 



2. Anthrax spores were killed after 24 hours' immersion in 



a five per cent, solution, but a one per cent, solution 

 failed even after two days. 



3. A five per cent, solution was ineffective for the tubercle 



bacillus. 



The disinfecting quality of this chemical depends on its property of 

 liberating a part of its oxygen very readily. When oxygen is in the 

 nascent condition, that is, immediately after its liberation, it possesses 

 powerful germicidal properties. Condy's fluid is largely made up of 

 this disinfectant. 



Sodium Chloride or Common Salt. Common salt, in the proportion 

 1 : 6, was formerly supposed to be an active germicide. Later, more 

 accurate experiments have not borne out this supposition. For 

 example, a saturated solution of common salt failed to destroy anthrax 



