INORGANIC ELEMENTS. I I 



ash ; carbonates and chlorides of the alkali metals make up the 

 remainder largely. 



In view of this composition of the body, it is important to 

 learn how its waste is replenished, and what substances must 

 be or may be consumed to repair the constant losses and 

 enable the body to do its proper work. This leads to the 

 question of foods or nutritives in the broad sense. Beginning 

 with the inorganic materials used by the body, we have first : 



Water. As it appears on the surface of the earth water 

 is classed conveniently as hard and soft. The descending 

 rain, after the dust is washed from the air, consists of nearly 

 chemically pure water. It holds no mineral matters dissolved, 

 and is contaminated mainly with a small amount of dissolved 

 carbon dioxide. Such water on reaching the earth is soft and 

 can replace distilled water for most purposes. The changes 

 which follow after contact with the soil depend on the compo- 

 sition of the latter. If the strata over which the water flows 

 or through which it percolates consist of sand, quartz or 

 silicate rocks or other insoluble materials the water is left 

 in practically pure condition, and is the water usually spoken 

 of as soft water. But, on the other hand, if the rain water 

 comes in contact with limestone, gypsum, or other slightly 

 soluble substances, something goes into solution and the 

 product is now known as hard water, the degree of " hard- 

 ness " depending on the amount of dissolved solids. Waters 

 containing the carbonates of calcium and magnesium are de- 

 scribed as temporarily hard, since the carbonic acid which 

 holds these carbonates in solution may be removed by boiling, 

 which causes precipitation. Calcium sulphate or chloride in 

 water can not be precipitated by boiling and the presence of 

 these and a few other substances produces permanent hardness. 



Moderate amounts of these mineral matters in water are not 

 objectionable; in fact waters with some lime and magnesia 

 are preferable to absolutely soft water for drinking purposes. 

 But along with the inorganic substances the water may take 

 other things from the soils with which it comes in contact that 



