152 



being obtained by the electrolysis of salt. This chloride of lime is com- 

 posed largely of calcium hypochlorite. When added to water this hypo- 

 chlorite dissolves, leaving a residue of calcium hydrate and calcium car- 

 bonate. Both of these substances are entirely harmless factors in a bath 

 water. The oxidizing power of the commercial chloride of lime is repre- 

 sented by about 35 per cent of available chlorine. It is nascent oxygen 

 that is the purifying factor, not the chlorine. 



The capacity of the Purdue swimming pool is 85,000 gallons, and 680 

 grams of the chloride of lime were used at each dose. This would be about 

 the equivalent of 20 pounds to the million gallons. Before starting the 

 experiment with the chemical, bacteriological analyses were made of the 

 water for a week, the pool being emptied twice. No attempt was made to 

 keep track of the number of bathers in the pool. 



The following table shows the results of the analyses for the week 

 before using the chemical dosage, compared with the results of the analyses 

 for the week while the dosage was going on. During the latter week, that 

 is. while the tank was being dosed with the chemical, the water was not. 

 changed at all. 



The method of applying the chemical was to sprinkle it on the surface 

 of the water in the pool. This was easily done with one trip around the 

 edge, throwing the powder as one walked. The time occupied in this 

 process was less than two minutes. 



No. of Bacteria 



Date. perc.c. B.ColL- 



Monday, November 1, pool just filled 560 . None 



Evening, after use 6,160 Present 



Tuesday a. in., November 2 20.650 Present 



Evening, after use 37.600 Present 



Wednesday a. m., November 3 27,800 Present 



Evening, after use 60,500 Present 



Tank emptied. 



Thursday a. m., just after filling 930 None 



Evening, after use S.500 Present 



Friday a. m.. temperature of water 85 Pahr 100.200 Present 



Evening, after use 106,400 Present 



Saturday a. m., November 6 118,000 Present 



Evening, after use 140,000 Present 



