151 
in some too expensive to change the water once or twice a week. At the 
Central Baths, Bradford, England, the water is filtered. The expense or 
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’ reported the use of a chemical, an “elec- 
trolytic fluid,” by the medical officer of health of the metropolitan borough 
LEE a ee 
Bom! - 
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. 
3efore finding this reference the writer had conducted a series of 
tests on the water of the swimming peol 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 
1 Scientific American Suppl. No. 1765, Oct. 30, 1909. 
