68 



MISCELLANEOUS PAPEKS. 



drinking water b}^ exposing it tb the action of clean metallic copper." 

 Perhaps this opinion should be qualilied by adding that the action i.s 

 more rapid if the water contains no free carbon dioxid, although the 

 following tables show onlj^ slight differences between the toxicit}^ of 

 metals because of the presence or absence of carbon dioxid. 



Table XXVIII. — Effect of carbon dioxid upon toxicity of metals to Bacillus coli.^ 



1 Experiment conducted in Weber resistance glass test tubes, cacli 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 Bacillm 

 coli received from Prof. Theobald Smith. The temperature during this experiment varied from 18° 

 to 22° C 



'Iron impure and presumably more toxic than pure iron. (See Table No. XXII.) 



Table XXIX. — Toxicitxj of metals to Bacilhis coli in the absence of carbon dioxid.^ 



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 



2 Iron impure and presumably moie toxic than pure iron. (See Table No. XXII.) 



« There is a seeming discrepancy in this statement due to the fact that Mr. Earle 

 B. Phelps, assistant hydrographer, U. S. Geological Survey, has carried on experi- 

 ments on the storage of typhoid infected water in copper canteens, some results of 

 which, with conclusions of a nature unfavorable to the use of metallic copper in 

 practically sterilizing water, were issued in a press circular of the Geological Survey. 

 A quotation from Mr. Phelps's paper paralleled with a quotation from Bureau of 

 Plant Industry Bulletin No. 76 shows clearly that Mr. Phelps's work is a corrobora- 

 tion instead of a contradiction of the fact reported in Bulletin No. 76 that metallic 

 copper has a high germicidal value. Mr. Phelps has stated: ' ' The fact that organisms 

 do survive the copper treatment even in small numbers [Per cent reduction usually 

 over 99.999.— K. F. K.] seems, in the writer's view, to lessen considerably the value 

 of the canteen as a safeguard against typhoid infection. A second point of interest 

 is the fact that the efficiency of the canteen decreases as time goes on, probably 

 . owing to the accumulation on the surface of the copper of a film of basic carbonate 

 or other insoluble copper compound." A paragraph from Bureau of Plant Industry 

 Bulletin No. 76 reads as follows: "Complete sterilization is a standard to which even 

 the best filters seldom attain, and under the most unfavorable conditions the reduc- 

 tion in the number of bacteria in water exposed to the action of metallic copper for 

 twelve hours will be approximately as great as filtered water. The copper must be 

 kept clean, not, as is popularly supposed, to i^rotect the consumer from copper 

 poisoning, but because it is. possible for the metal to become so coated with foreign 

 substances that there is no longer any contact of copper and water, and hence no 

 antiseptic action." 

 100— vn 



