151 



in some too expensive to change the water once or twice a week. At the 

 Central Baths, Bradford, England, the water is Altered. The expense of 

 pumping the water and caring for the filter does not make the filtration 

 process a particularly economical one. 



It occurred to the writer that some chemical, as copper sulphate or 

 chloride of lime, both of which are being used extensively in the purifica- 

 tion of sewage and sewage polluted waters, might be used in the treatment 

 of swimming pool waters with but small expense. Inquiries in many di- 

 rections and a careful search in available literature resulted in but scant 

 information. A single reference 1 reported the use of a chemical, an "elec- 

 trolytic fluid," by the medical officer of health of the metropolitan borough 



- 



I I- 1 * i; fiPiiiii -jpl 



Fig. 5. Plunge, East 23d St. Public Bath, New York City. (A fairly well lighted 

 indoor pool.) By courtesy of "Modern Sanitation." 



of Poplar, Mr. F. W. Alexander. This fluid is obtained by the electrolysis 

 of a solution containing magnesium chloride, the result being a solution 

 of magnesium hypochlorite. Treatment of water in swimming baths by 

 this fluid was thought to be simple, economical and efficient, bacteriological 

 tests on water so treated giving sterile results. 



Before finding this reference the writer had conducted a series of 

 tests on the water of the swimming pool at the Purdue gymnasium, using 

 chloride of lime. 



Commercial chloride of lime (bleaching powder) is usually manufac- 

 tured by passing dry chlorine gas over freshly slaked lime, the chlorine 



Scientific American Suppl. No. ] 7G5, Oct. .°.0. 1009. 



