WATER 59 



sorb moisture from the air. Such substances are called 

 deliquescent. Water takes an important part in chem- 

 ical reactions ; in fact, many of the reactions expressed 

 in the form of equations could not take place without the 

 presence of water. 



62. Natural Waters. Rain, spring, lake, river, and 

 sea waters are some of the principal forms in which water 

 is found in nature. Some waters contain a sufficient 

 amount of dissolved salts to give them 



definite characteristics. Such are 

 known as mineral waters. The most 

 common impurities in water are lime, 

 magnesia, potash, soda, and iron com- 

 pounds. These substances give prop- 

 erties to the water which cause them 

 to be characterized as hard or soft, Typhoid'b 3 aciiius. 

 according to the nature and amount of minerals dis- 

 solved. All natural waters are liable to contamination, 

 and the organic impurities of water serve as food for dis- 

 ease-producing organisms. The sanitary condition of 

 the water supply has an important bearing upon health. 

 Typhoid fever, cholera, and other bacterial diseases are 

 frequently caused by poor drinking water. The spores 

 of the organisms present in the water are taken into the 

 body where they rapidly multiply. Surface wells, par- 

 ticularly when near barns and dwellings, and in thickly 

 settled regions, are frequently in an unsanitary condition. 



63. Impurities in Water. The nature of the impuri- 

 ties in the soil through which water flows determines the 

 kinds of impurities in the water. If a soil is polluted 



