66 The Philippine Journal of Science wis 



practical. In practice one of the first substances to be used 

 was quicklime. However, a large amount must be added in order 

 to obtain efficient disinfection, and it often happens that sufficient 

 precipitate is formed greatly to increase the turbidity of the 

 water. Copper sulphate has had various advocates,* but while 

 it is very useful when used against plant contaminations such 

 as algse, it cannot take front rank so far as its bactericidal re- 

 sults are concerned. It, too, has the disadvantage of greatly 

 increasing the turbidity of certain waters. 



Chlorine and compounds like hypochlorites, from which chlo- 

 rine is readily liberated, are comparatively cheap and are much 

 used. They are thought to owe their germicidal action to the 

 liberation of oxygen, thus acting like ozone. They seldom pro- 

 duce undesirable precipitates and have little toxicity. Anti- 

 formin has been recommended as a disinfectant by Uhlenhuth 

 and Xylander.* Phelps ^^ found that the chlorine was not liber- 

 ated as rapidly from it as from hypochlorite of calcium, but 

 that its use was not more efficient in reducing bacterial content. 



Hypochlorite of calcium still seems to be, according to many 

 investigators, the most generally useful disinfectant for sewage 

 and for potable and bath water. Manheimer ^' recommends its 

 use, testing the water from time to time in order to determine 

 that a trace of chlorine is kept constantly present. Bunker " 

 found that the addition of bleaching powder in quantities suffi- 

 cient to give one part available chlorine in 2,000,000 parts of 

 water kept the water sterile for four days with constant use of 

 the pool. He recommended the application of the disinfectant 

 twice a week for the average pool, to insure practically sterile 

 water. 



At the University of Wisconsin tank, which has a capacity 

 of 97,000 gallons, Ravenel " found that there was a gradual 

 increase in the number of bacteria to the middle of the week, 

 then a decrease, but another increase on Saturday. Treating 

 250 cubic centimeter samples of water with calcium hypochlorite 

 for thirty minutes, it was found that about 0.5 part of available 

 chlorine per million parts of water materially reduced the bac- 

 terial content and usually destroyed the colon bacilli. One 



'Stokes, Am. Med. (1905), 10, 1075; Burrage, Proc. Ind. Assoc. Set. 

 (1909); Rettger and Markey, Eng. News (1911), 66, 699. 

 'Berl. klin. Wochenschr. (1908), 46, 1346. 



"Phelps, E. B., Gesundheits-Ingenieur. Anklam, Munich (1910), 407. 

 ''Pub. Health Rep. (1915), 30, 2796. 

 "Science (1910), n. s. 31, 556. 

 "Am. Phy. Ed. Rev. (1912), 17, 684. 



