COLLOIDAL SOLUTIONS. 



37 



electrical method may be perfected for rapidly obtaining a strong 

 colloidal solution, which frill furnish a more convenient means of 

 application than that of the crude salt. 



In regard to the bacteria causing cholera and typhoid, the impor- 

 tance of the specific toxic effect of colloidal copper is probably much 

 greater than with algae. The following tables show the proportions 

 of the area of copper to the quantity of water and to the time and the 

 temperature necessary to produce the complete sterilization of water 

 containing these pathogenic germs: 



Effect upon Bacillus typhi of exposure to colloidal solution of copper at room temperature. 



[Determination made in tubes of bouillon. -f indicates growth after 48 hours' inoculation; indi- 

 cates no growth.] 



a Experiment conducted in test tubes containing 10 cc. each of sterilized water. The copper foil 

 was sterilized and added immediately before inoculating the tubes with the usual 3 mm. loop of a 

 24-hour culture of B. typhi. This experiment was duplicated with three separate strains of typhoid 

 with identical results. 



Effect upon Bacillus typhi of exposure to colloidal solution of copper at room temperature. 

 [Determination made in Petri dishes.] 



Experiment conducted in test tubes, each containing 5 cc. of sterilized water. The copper foil 

 was sterilized, and added immediately before inoculating the tubes with the usual 3 mm. loop of a 

 24-hour culture of B. typhi. 



