COLLOIDAL SOLUTIONS. 



39 



Effect upon jxirati/phoiil of expoxurr t<> colloidal solution of copper til room temperature. » 



[DeteriiiiiiHti..ii iniuU- in tubes i.f bouillon. + indicates Krowth after is hours' inoeuliition; indi- 

 cates no growth.] 



Duration of exposure to iielion of eopiier. 



10 hours. 

 10 hours. 

 20 hours. 

 50 hours. 



Cheek. 



15 s<i. mm. 100 s<i. mm. 22r> scj. mm. 

 eopper toil copper foil copper foil 

 in U) < c. of in 10 cc. of ' in 10 (•<■. of 



water. 



+ 



+ 

 + 

 + 



+ 



+ 

 + 



+ 



water. 



+ 

 + 



water. 



«E.xperiment coiKlucted in test tuh.-s coniainiuff 10 cc. each of sterilized water. Tlie co[.per foil 

 was sterilized ami added immediately before inoculating the tubes with the usual 3 mm. loop ot a 

 24-honr culture of paratyphoid. 



Effect upon Microspira comma of colloidal xohition of copper at rariouK temperatnrett. " 



<( Experiments conducted in test tubes, eaeh containing 5 cc. of sterilized water, portions of which 

 had been previously treated with the desired amo\nits of copper sulphate. .\11 tuljes inoculated with 

 a 3 mm. loop of a l-i-hour cidtnre of ^f. coniiiia. 



It is evident that the amount of surface exposed in an}' ordinaiy 

 copper tank would far- exceed the amount demanded for the above 

 results, and it is likewise certain that after standing from 6 to 8 hours 

 at room temperature in a e/ea/t copper vessel water becomes safe to 

 drink even though it may have contained cholera and typhoid germs. 

 It remains to be seen whether or not the application of these facts to 

 conditions in the Tropics, where cholera is abundant, will be of any 

 value. It would .seem that the con.struction of canteens and other 

 water vessels from copper might serve as an additional safeguard, if 

 not an actual preventive of this disease, and would prove of consider- 

 able value where distillation or efficient filtration apparatus is not at 

 hand. 



