~]311] SCIENTIFIC MANUAL. 25 



Kainit is being extensively used, as a source of potash, 

 by manufacturers of commercial fertilizers. 



Nitrate of Potash, or saltpetre, is another form in which 

 it is used for agricultural purposes, but it is more expen- 

 sive, on account of its combination with nitrogen. It is 

 obtained from soils in India, and from "nitre beds" in 

 Europe, where refuse lime and animal manures are thrown 

 -up in loose heaps, exposed to the air, but protected from 

 rain. It is allowed to remain for several years, when water 

 is leached through it, and then collected and evaporated, 

 leaving the crystallized nitre. 



Soda, like potash, is a compound of oxygen, with a soft, 

 white metal, called sodium, which has to be kept under 

 naptha-oil to prevent its catching fire. It also burns on 

 water. 



Soda is caustic in its action, and, when combined with 

 : carbonic acid, is known as carbonate of soda, or sal-soda. 



In nature, soda occurs chiefly in common salt, or chlo- 

 ride of sodium. 



The waters of the ocean contain so much of this salt 

 -as to make them unfit for drinking purposes. 



The chief source of our salt supply is in the evaporation 

 of the sea water, which is carried on extensively along the 

 shores of the Mediterranean Sea. Each gallon of water 

 -contains about four ounces of salt. 



Immense beds of salt occur in some parts of the world, 

 and afford another source of supply. This is called rock 

 Salt, from its massive rock-like appearance. It is quarried 

 and crushed to different degrees of fineness. 



Large quantities of salt are also obtained by evaporating 

 the waters of salt springs, which occur at Syracuse in New 

 York, in Western Pennsylvania, Ohio, West Virginia, 

 Michigan, and some of the Western States and Territories. 



There were produced in the United States, in 1870, 

 17,606,105 bushels of salt, valued at $4,818,229. 



When the evaporation takes place rapidly, the crystals 



