Effect of Acids on Typhoid and Colon Bacilli 261 



oxidizing agents, and less with acids and bases. Disinfectants them- 

 selves of organic nature were least afifccted. 



The particular phase of the subject with which we are especially 

 concerned, the disinfectant action of the acids, was not exhaus- 

 tively treated in this investigation. One series of experiments was 

 made with normal and half-normal solutions, in which it was found 

 that hydrofluoric, nitric, and trichloracetic acids in normal strength 

 killed all the anthrax spores in 120 minutes. Normal chloric, hydro- 

 bromic, and hydrochloric acids and half-normal oxalic acid left a few 

 spores alive after eight hours. Normal sulphuric acid was a little 

 less effective, and normal phosphoric, formic, and acetic acids kft 

 large numbers of organisms alive after eight hours. Hydrocyanic 

 acid in normal strength showed little action even after 30 hours. 

 The investigators conclude that there is a general relation between the 

 action of the acids and the amount of dissociated hydrogen present ; 

 but there appear many exceptions to a strict parallelism. The 

 authors attribute these exceptional effects to the anion or the undis- 

 sociated molecule, and point out that in more dilute solutions they 

 tend to disappear. Thus, 0.06 normal solutions of hydrochloric, 

 chloric, nitric, and trichloracetic acids showed about the same 

 disinfectant action, apparently due to the presence of an approxi- 

 mately equal amount of dissociated hydrogen. 



At a still earlier period a somewhat similar series of investigations 

 to those of Paul and Kronig had been carried out in another field. 

 This was a study of the relation between toxicity and dissociation 

 as measured by the effect of various salts and bases, and a long 

 series of organic and inorganic acids, on the higher plants, by 

 Kahlenberg and True (1896). Their method consisted in determin- 

 ing the maximum strength of solution in which seedlings of Lupinus 

 alhus could grow. The seedlings were exposed for 15 to 24 hours, 

 and their condition determined by their general appearance and by 

 the growth which had taken place. These plants proved very 

 sensitive to the action of dilute acid, a strength of from 0.00008 to 

 0.00064 normal killing them in almost ever)' case. It is interesting 

 to note that boric acid was endured in 10 times this strength. In 

 general, the poisonous action ran parallel with tiie degree of dis- 

 sociation, but certain of the organic acids showed relations of thiir 



