72 PUBLIC HEALTH CHEMISTRY 



Ground Water Is divided into (i) Moisture, which is 

 the water present along with ground air, simply moistening 

 the particles ; and (2) Subsoil water, which is the condition 

 when the particles and their interstices are full of water. 



The amount of moisture in a soil is estimated by drying 

 a weighed portion of it ; the loss of weight being calculated 

 as moisture. 



The level of the subsoil water is studied by digging a pit 

 or well, and observing from time to time the varying levels. 



Soil Temperature Is taken at the depth of 4 feet by a 

 specially sluggish thermometer, enclosed in a protecting 

 case. The soil temperature attains its maximum in July 

 and August. 



Soil is also examined chemically for total nitrogen, 

 phosphates, sulphates, nitrates, and peaty acids. An 

 aqueous extract of a weighed quantity of it may be 

 examined for chlorides, ammonias, etc. It is also separated 

 mechanically into particles of different sizes, and into clay, 

 sand, etc. 



