EFFECT OF COPPER UPOInT WATER BACTERIA. 



69 



To determine whether the peculiar variation in the germicidal power 

 of sohitious or metals is due to the use of ordinary laboratory glassware 

 made of a rather soluble glass instead of carefull}" selected highly 

 insoluble glass, a parallel series in good and poor glass was carried on. 

 The following tables show the slight difference in results: 



Table XXX. — Efect of glass upon toxicity of metals to Bacillus coli.^ 



i;uration of exposure to action of metals. I Check. Copper. Iron. 



Zinc. 



Lead. 



Tin. 









Colonies. 



Colonies. 



Colonies. 



1,925 



1,850 



2,450 



775 



2,100 



715 



525 



2,350 



70 



15 



4.350 



1 



i Colonies. 



hour ! 2, 600 



2 hours I 2, 650 



6 hours j 2, 700 



24 hours 28, 000 



Colonies. 



2,600 



2,800 



2,450 



13,750 



Colonies. 

 8,100 

 2,300 

 4. 200 

 12. 000 



^ Experiment conducted in ordinary glass test tubes each containing 10 c. c. of Avater triple distilled 

 from glass, to portions of which were added sterile blocks of the proper metals, each having approxi- 

 inately 2 sq. cm. surface area. 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. 



Table XXXI. — Effect of glass upon toxicity of metals to Bacillus coli.^ 



Duration of exposure to action of metals. Check. Copper. Iron. Zinc. Lead. Tin. 



Colonies. Colonies. 



hour ' 2, 300 4, 825 



2 hours 1,572 975 



6 hours 1,400 190 



24 hours 10,825 1 



Colonies. 

 4,750 

 2,400 

 3,050 

 6,700 



Colonies. 



2,400 



200 



20 



1 



Colonies. 

 2,800 

 1,800 

 2,000 

 19. 000 



Colonies. 



3,000 



3,600 



3, 8.50 



14.000 



1 Experiment conducted in Weber resistance glass test tubes each containing 10 c. c. of water triple 

 distilled from glass, to portions of which were added sterile blocks of the proper metals, each having 

 approximately 2 sq. cm. surface area. 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. 



COPPER SULFATE AND FILTRATION. 



The use of copper sulfate in connection with filtration has been 

 mentioned in previous bulletins. Further experiments in this field 

 show that in mechanical filtration with alum it is necessary to limit 

 the use of copper sulfate to treatment some hours before coagula- 

 tion. When solutions of aluminum sulfate and copper sulfate are 

 mixed and alkali or hard water is added in quantities sufiicient to 

 cause precipitation the copper is coagulated at once, while the alu- 

 minum is deposited on the copper and incloses it, with the result that 

 the copper-alum coagulum is no more toxic than is the pure alum coag- 

 ulum. When copper and iron salts are precipitated together the 

 reverse of this seems to take place and the precipitate retains its toxic 

 properties." 



« See also H. AY. Clark, Sulphate of Aluaiina as a Germicide. Thirty-sixth Annual 

 Keport of State Board of Health of Massachusetts, 1904, p. 288. 



100— vu 



