WATER 



IE WATER _-_ 





CHARCOAL 





-RESERVOIR. 



such waters except by distillation. Different kinds of 

 mineral matter, if present in excessive amounts, may im- 

 part medicinal properties ; magnesium sulfate (Epsom 

 salts) acts as a purgative, 

 while calcium sulfate causes 

 costiveness. Strong alkaline 

 waters can generally be de- 

 tected by their salty taste. 



The presence of a large 

 amount of limestone in waters 

 is not so serious as the pres- 

 ence of other minerals . Waters 

 sometimes contain limestone 

 to such an extent that when 

 boiled they become cloudy, 

 which is because of the re- 

 moval Of the Carbonic acid Fig 33-Charcoal water filter. 



gas ; this caused the limestone to remain in solution. 



Waters that contain limestone are not generally consid- 

 ered injurious to health although they 

 are not so satisfactory for cleaning pur- 

 poses on account of the lime acting upon 

 the soap and forming a scum of insoluble 

 lime soap. A large amount of lime- 

 stone, gypsum, etc., is what causes waters 

 to be hard. Some waters contain iron 

 compounds, as carbonate of iron which, 

 upon contact with the air, forms hydrate 



of iron, and is deposited as a brownish red sediment. 



Some waters contain so much mineral matter that when 



ig- 34. Unglazed 



porcelain filter. 



