636 A MANUAL OF BACTERIOLOGY 



therefore very variable. The reduction in germicidal 

 power by addition of sodium chloride is well seen from the 

 following results (Finlay, loc. cit.) : 



Number of colonies 



16 litres of solution contained developing after treat- 



ment for 6 minutes. 



1 mole HgCl 2 8 



1 HgCl 2 + 1 mole NaCl . . 32 



1 HgCl 2 + 2 moles NaCl . . 124 



1 HgCl 2 + 4 Nad . . 382 



1 HgCl 2 + 10 NaCl . . 1087 



Extremely high values were at one time given for the 

 germicidal efficiency of corrosive sublimate. This is now 

 known to have been due to its powerful inhibitory action, 

 traces of the substance carried over into the subcultures 

 preventing growth (see p. 643). 



The Local Government Board recommended the fol- 

 lowing solution of corrosive sublimate for disinfecting 

 purposes : 



Corrosive sublimate J oz. 



Hydrochloric acid . . . 1 oz. fl. 



Anilin blue . . . . . 5 gr. 



Water 3 gals. 



This forms a solution of 1-900 nearly ; it would be pre- 

 ferable to use 1 oz. of corrosive sublimate. 



The biniodide is also a powerful disinfectant when 

 dissolved in potassium iodide. It is not affected by 

 albuminoids nearly as much as is per chloride, and may 

 be incorporated with soap. 



Soluble silver salts are powerful disinfectants, weaker 

 than mercuric chloride, but far less sensitive to albumi- 

 noids ; in blood-serum, for instance, silver nitrate is 

 several times as powerful as corrosive sublimate. They 

 are incompatible with chlorides, except in certain organic 



