112 The Philippine Journal of Science ms 



ably to affect the alkalinity or total solid content of the water 

 (Tables V to VII). 



It might be well to note parenthetically that although the last- 

 mentioned concentration is far in excess of that generally em- 

 ployed for purification, there was no complaint from users of 

 the pool, except in one case, where a few people complained of 

 irritations of the eyes and of the mucosae of nose and throat. 

 In this instance it was shown that the trouble was due to careless 

 and improper administration of the disinfectant, which allowed 

 undissolved lumps to get into the tank. The odor was strong 

 and persisted for days, but was not sufficiently disagreeable to be 

 a real drawback to the use of hypochlorite. 



The chlorination having failed to give the desired results, an 

 attempt was made to study in detail the causes of the failure 

 and to overcome the difficulties involved. 



It was noticed that in general the city water showed no trace 

 of "free chlorine" when it left the mains, as determined chemi- 

 cally by acidifying 200 cubic .centimeter samples of water and 

 adding a drop of methyl orange,^ the presence of chlorine being 

 indicated by the bleaching of the indicator. This result was 

 rather surprising, since the water arrived at the swimming pools 

 probably within three, almost certainly within five, hours after 

 chlorination had taken place. Moreover, in spite of the relatively 

 large additions of chloride of lime to the swimming pools, all trace 

 of "free chlorine" was lost, usually within twenty-four hours. 



A laboratory study of the decomposition of a clear (filtered) 

 solution of chloride of lime added to (unchlorinated) city water 

 gave the results indicated in Table VIII (fig. 1). 



Table VIII. — Decomposition of chloride of lime in water. 



,,. . Available chlorine in 



*^'""t«- parts per miUion. 



0.8 



2 0.6 



30 0.3 



120 0.1 (?) 



From the foregoing it is apparent that the chloride of lime 

 lost its effective strength very rapidly and that in two hours 

 its concentration had fallen below 0.1 per million. Just what 

 is the minimum concentration of chlorine that will keep water 

 free from dangerous organisms is not known ; certainly it cannot 

 be much less than the concentration mentioned above. 



"Winkler, Zeitschr. f. angew. Chem. (1915), 28, I, 22. 



