XI, A, 3 Heise and Aguilar: Purification of Swimming Pools 113 



0.8 



0.7 



0.3 - 



30 



Time in minutes. 

 SO 60 70 eo 



1 



120 



Fig. 1. Decomposition of calcium hypochlorite in water. 



The destruction of hypochlorite must be due either to sponta- 

 neous decomposition or to interaction with substances dissolved 

 in water. Hypochlorites decompose, even in the dark," with 

 measureable velocity. The reaction is greatly accelerated by 

 light,' especially by the visible and ultra-violet rays, and by heat. 

 The temperature of a bath, therefore, becomes a matter of no 

 small importance in studying purification of water with hypo- 

 chlorite, and the amount of daylight falling on a pool may greatly 

 affect the rate at which hypochlorite disappears. 



The interaction of chlorine with substances dissolved in water 

 has been much studied in recent years.* The phenomenon is 

 generally associated with a high organic content in water. A 

 large amount of "free chlorine" disappears immediately, after 

 which decomposition proceeds more slowly, but does not reach 

 equilibrium for a long time. The amount of chlorine consumed 

 appears to be dependent on the concentration in which it is 

 added ; the more hypochlorite added, the more will be decomposed 

 in a given time. The reaction proceeds more rapidly at high 

 temperature than at low. 



"Bhaduri, Zeitschr. f. anorg. Chem. (1897), 13, 385. 

 ' Lewis, Journ. Chem. Soc. (1912), 101, 2371. 



*Cf. Glaser, Arch. f. Hyg. (1912-13), 77, 165; Hairi, Zeitschr. f. Hyg. 

 (1913), 75, 40. 



