118 



The Philippine Journal of Science 

 Table XII. — Effect of adding antiformin. 



[Results expressed as parts per million.] 



1916 



Age of water in days. 



Turbid- 

 ity. 



Qualitative test for free chlorine. 



Chlorine 

 consump- 

 tion." 



1 



8.5 

 <7 

 <7 

 <7 

 <7 

 <7 







2 



, . do - 





3 



do — 



1.0 

 2.4 

 2.8 

 4.2 



4 



, 



5 



do 



6 



do 







* Two hundred cubic centimeter samples digested two hours at 30° C. with 3.5 milligrams 

 available chlorine. 



In order to ascertain whether the quantity of disinfectant 

 could be appreciably diminished without destroying the steriliz- 

 ing efficiency of the hypochlorite, a final series was attempted, 

 using daily additions of 0.25 part of available chlorine per million 

 parts of water. It developed that, although tank I was kept 

 sterile by this treatment, the bacteria count in tank III showed 

 a rather alarming increase after about three days, in spite of the 

 fact that tank I is used by more bathers than tank III. The 

 building operations at tank III introduced disturbing factors; 

 however, there can be little question that in this case light was 

 the chief cause of the discrepancies noted. Tank III is built 

 practically out of doors, and during the last week's run was open 

 to the sky. The sunlight had sufficient accelerating effect on 

 the decomposition of the hypochlorite to bring the available 

 chlorine below the effective sterilizing strength in a short time. 



The effect of additions of 0.25 part of available chlorine per 

 million parts of water is shown in Table XIII. Chlorine con- 

 sumption was determined by digestion both in the dark and in 

 the diffused daylight of the laboratory. The differences noted 

 in the two determinations give some indication of the marked 

 effect of light. 



It is doubtful if such high concentrations of hypochlorite as 

 those used in Manila would be necessary under average condi- 

 tions. In addition to the poor quality of the water, the added 

 effects of excessive temperature (almost 30 °C.) and of light 

 must be taken into account. Even in the tanks under obser- 

 vation, where conditions were fairly uniform, each case required 

 special treatment. Tank III, the best lighted, requires greater 

 additions of chlorine to maintain an excess of disinfectant than 

 does tank I, while in tank II, the most poorly lighted, the decom- 



