156 BACTERIOLOGY. 



A BRIEF DESCRIPTION OF SOME OF THE MORE 

 COMMONLY USED DISINFECTANTS. 



Bichloride of Mercury. This substance, when present 

 in 1 part in 1,000,000 in nutrient gelatin or bouillon, 

 prevents the development of parasitic bacteria. In 

 water 1 part in 500,000 will kill many varieties in a 

 few minutes, but in bouillon twenty-four hours may 

 be needed. With organic substances its power is less- 

 ened, so that 1 part to 1000 may be required. Spores 

 are killed in 1 to 1000 watery solution within one hour. 

 Corrosive sublimate, as seen in the figures given above, 

 is less effective as a germicide in alkaline fluids con- 

 taining much albuminous substance than in watery 

 solution. In such fluids, beside loss in other ways, 

 precipitates of albuminate of mercury are formed 

 which are at first insoluble, so that a part of the mer- 

 curic salt does not really exert any action. In alkaline 

 solutions, such as blood, blood- serum, pus, tissue-fluids, 

 etc., the soluble compounds of mercury are converted 

 into oxides or hydroxides. The soluble compounds 

 can, of course, remain in solution only when there are 

 present sufficient quantities of certain bodies which 

 render solution possible. Bodies of this sort are espe- 

 cially the alkaline chlorides and iodides, and, above all, 

 sodium chloride and ammonium chloride. A very 

 simple way of preventing precipitation of the mer- 

 cury, then, is to add a suitable quantity of common 

 salt to the corrosive sublimate. Those compounds of 

 mercury which, like the cyanides, are not precipitated 

 with alkalies, because they at once form double salts, 

 require no addition of salt. 



For ordinary use, where corrosive sublimate is em- 



