THE INHIBITING EFFECT OF CERTAIN ORGANIC SUB- 

 STANCES UPON THE GERMICIDAL ACTION 

 OF COPPER SULPHATE.* 



EARLE B. PHELPS. 



(From the Sanitary Research Laboratory and Sewage Experiment Station of the Massachusetts Institute 



of Technology.) 



INTRODUCTION. 



THE germicidal action of copper salts dissolved in water has fre- 

 quently been found to depend largely upon the character of the water 

 itself. Ellms (1905) has pointed out the influence of the hardness and 

 turbidity of the water. Johnson and Copeland (1905) found that in 

 a sewage effluent, to which a large number of typhoid organisms had 

 been added, an amount of copper sulphate equal to a concentration of 

 20 parts of copper per million reduced the number of bacteria from 

 1,300,000 to 600 per cubic centimeter in 15 hours. In distilled water, 

 other conditions being the same, the reduction was from 1,300,000 to 

 ii. Kraemer (1905) and Basset-Smith (1905) have both shown that 

 the toxic action of copper on the typhoid organism is much greater in 

 distilled water than in tap water. 



It is not difficult to determine the nature of the influence exerted 

 by mineral impurities in the water. Dissolved carbonates bring about 

 a direct precipitation of the copper. Even such insoluble material as 

 kaolin has been shown by Sullivan (1905) to possess the power of 

 reacting with copper salts, in some cases completely removing the 

 copper from solution. True and Oglevee (1905) have confirmed the 

 earlier results of Nageli showing that adsorption often plays an impor- 

 tant role, and that powdered glass or sand may destroy in large meas- 

 ure the toxic action of dilute metallic solutions. 



In case of organic impurities the nature of the influence is not 

 quite so clear. Direct precipitation of the copper may occur, especially 

 in sewages. On the other hand, the presence of certain classes of 

 organic matter, such as leaf infusion, has been shown to prevent the 

 precipitation of copper by alkaline carbonates (Ellms, 1905). In such 



*Received for publication March 28, 1006. 



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