xii. a, i Heise: Chloride of Lime 19 



in bacterial content of waters in municipal distribution systems 

 at varying periods after chlorination.(i5) 



Much work remains to be done on the substances formed 

 by the interaction of hypochlorites with the organic matter 

 found in water. It is because of these substitution pro- 

 ducts (16, 20) that chlorinated waters used for public supplies 

 often retain a peculiar chlorine odor and taste after all chem- 

 ical trace of free chlorine has disappeared. In such cases — (21) 



these tastes and odours are not occasioned so much by chlorine or hypo- 

 chlorites themselves as by inorganic and organic chloramines, and possibly 

 other chlorine-substituted compounds formed by interaction with the 

 organic matters present in waters. * * * They [the chloramines] are 

 all germicidal, and all possess a more or less disagreeable odour. * * * 

 He [Rideal] proved that chlorine * * * was working by substitution 

 for hydrogen in ammonia and organic compounds, yielding products [chlora- 

 mine and hydrazine] of higher germicidal power than chlorine itself. 



Race (19) found that when ammonia was added to hypo- 

 chlorites, in the proportion of 1 part ammonia to 2 parts of avail- 

 able chlorine, the germicidal action was increased threefold. 



While the addition of alum causes an immediate reduction 

 in available chlorine, it has no apparent effect on the bacte- 

 ricidal properties of the solution for twelve hours, according 

 to the findings of Avery and Lye. (l) 



With waters high in organic matter it is probable that the 

 main chemical change follows the course of a monomolecular re- 

 action as in the case in the decomposition of hypochlorites in 

 distilled water. However, there are, apparently, so many simul- 

 taneous reactions that the accurate determination of the veloc- 

 ity constant is not easy. From the fact that, in general, the 

 amount of chlorine consumed by sewage in a given time is pro- 

 portional to the amount of chlorine added, Glaser(5) concluded 

 that the reaction is monomolecular. Race (18) followed the course 

 of the reaction between hypochlorites and a colored water and 

 came to the same conclusion. 



The effect of light, though a most important factor in the 

 decomposition rate of hypochlorites, has been frequently over- 

 looked or at least insufficiently emphasized, so that some of the 

 work which has been done is not conclusive. The importance of 

 this factor in the sterilization of swimming pools has already 

 been discussed. (10) 



EXPERIMENTAL PART 



Determination of available chlorine. — For the work recorded 

 in this paper, chlorine was quantitatively determined in the 



