NITROGEN FIXATION LOF 207 



pose, but, first, a brief reference will be made to the other two 

 sources of inorganic nitrogen, viz, Chile saltpeter and by-product 

 ammonium sulphate. 



CHILE SALTPETER 



Chile saltpeter is chemically known as sodium nitrate (NaN0 3 ), 

 the commercial product containing about 95 per cent nitrate, of 

 which 15y 2 per cent is nitrogen. Like the potash deposits in Ger- 

 many, there are few natural deposits like the saltpeter deposits in 

 Chile on the west coast of South America. These deposits were 

 discovered by Indians about 1809, who, when lighting a fire, noticed 

 that the ground began to ignite in various directions. They at- 

 tributed this to evil spirits and consulted a priest, who caused the 

 earth to be examined, thus revealing the presence of nitrate of soda. 



The nitrate deposits are located, at altitudes ranging from 2,000 

 to 6,000 feet, in the desert regions between the 12° and 26° latitudes, 

 a distance of about 500 miles, and perhaps the driest country in 

 the world, with no vegetation whatever. 



The nitrate beds generally form horizontal layers covered by 

 three distinct layers or strata of silica, calcium sulphate, and other 

 minerals, the thickness of these layers ranging from 2 to several 

 feet. The nitrate as mined goes under the name " caliche," and the 

 deposits vary in thickness from a few inches to 4 or 5 feet or more. 

 It is like a cemented gravel, the cementing material being the so- 

 dium nitrate and sodium chloride and other salts which accompany 

 it. The caliche treated runs from 14 per cent nitrate up to as high 

 as 30 per cent or more, and it does not as yet pay to mine materials 

 with less than 13 to 14 per cent nitrate. 



There are many theories advanced regarding the origin of these 

 natural nitrate deposits. Some think that they are original guano 

 deposits; others ascribe their origin to seaweed, because the caliche 

 contains considerable amounts of iodine, and fish skeletons are often 

 found embedded in the strata. Recent theories are that it has its 

 origin in volcanic actions. 



PREPARATION OF THE NITRATE 



The production of Chile saltpeter comes under two divisions — 

 the mining of the caliche and the refining. The caliche is extracted 

 from the ground by blasting and hand picking, after which it is 

 loaded in carts or light railroad cars and hauled to the refining 

 plants, called " oficinas," by mules or small locomotives. At the plant 

 it is crushed and leached with boiling water, when, due to the dif- 

 ferent solubility of the nitrate and chloride salts, practically all the 



