66 



MISCELLANEOUS PAPEKS. 



Table XXV. — Toxicity of copper sulfate to Bacillus coli in tap irater free of carbon dioxid. ' 



1 part copper sulfate to — 



Duration of exposure to action of copper j Qj^g„^ I jq qqq 

 ■^^^^^^^' j ■ I parts of 



water. 



hour. . 

 2 hours. 

 6 hours. 

 24 hours 



Colonies. 



4,600 



1,450 



1,500 



250 



Colonies. 



1,SOO 















50,0C0 1 100,000 

 parts of ^ parts of 



water. 



Colonies. 



4,800 















water. 



Colonies. 



3,700 



20 











500,000 



parts of 



water. 



Colonies. 



4,. 500 



80 



5 







1,000,000 

 I)arts of 

 water. 



Colonies. 



4,000 

 100 



2 







1 Experiment conducted in Weber resistance glass test tubes, each containing 10 c. c. of Potomac tap 

 water, portions of Miiich had been treated previously with the desired amount of copper sulfate. 

 All tubes inoculated with a 2 mm. loop of culture of Baei/lim eoli. received from Prof. Theobald Smith. 

 The temperature during this experiment varied from 18"^ to 22° C. 



Table XXVI. — Effect of carbon dioxid upon toxicity of copper sulfate to Bacillus coli.^ 



Duration of exposure to action of copper 

 sulfate. 1 



Check. 



1 part copper sulfate to- 



1 Colonies. 



hour 4, 200 



2 hours ' 2. 800 



6 hours ] , 460 



24 hours 1 , 540 



10,000 

 parts of 

 water. 



50,000 



parts of 



water. 



Colonies. 



"4,000 



10 



15 







Colonies. 



9,800 







15 







100,000 

 parts of 

 water. 



Colonies. 



1,270 







20 







500,000 



parts of 



water. 



Colonies. 



5,100 



110 



10 







1.000,000 



parts of 



water. 



Colonies. 



1,100 



260 



35 







Table XXVII. — Effect of carbon dioxid upon toxicity of copper sulfate to Bacillus coli.'^ 



1 Experiment conducted in Weber resistance glass te.st tubes, each containing 10 c. c. of Potomac tap 

 water, portions of which had been treated previously with the de.sired amount of copper sulfate. 

 All tubes inoculated with a 2 mm. loop of culture of Bacillus coli received from Prof. Theobald Smith. 

 The temperature during this experiment varied from 18° to 22° C. 



An examination of the foregoing tables shows that with the three 

 types of water the presence of carbon dioxid increases the resistance of 

 the bacilli in question. In the solution containing monocarbonate of 

 lime and copper sulfate the bacteria are extremely sensitive, even the 

 bacteria in the check solutions dA^ng rapidly, while in the solutions 

 charged with carbon dioxid the bacteria were able to persist in con- 

 siderable numbers in the dilute copper solutions in spite of the fact 

 that most of the copper must have remained in solution. This point 

 is interesting in connection with the work of Engels," who reports a 



« Weitere Studien iiber die Sterilization von Trinkwasser auf chemischen Wege. 

 Centralbl. f. Bakt., Parasit., u. Infekt., vol. 32 Orig., 1902, pp. 495-521. 

 100— VII 



