THE NITRATE DEPOSITS OF CHILE 31 



different purposes, but by far the largest consumption is its use as an 

 agricultural fertilizer, in supplying nitrogen to the soil. One of its 

 earliest uses, and still a source of large consumption, is in the manu- 

 facture of niter, or potassium nitrate, for gunpowder. This is done 

 by treating sodium nitrate with a salt of potassium. The nitrate 

 of Chile is also used in the manufacture of nitric acid, and as nitric 

 acid is an important factor in the manufacture of nitro-glycerine, 

 dynamite, and other explosives, the consumption of Chile nitrate 

 for such purposes is large. It is also used for many other chemical 

 purposes on a smaller scale. 



The value of sodium nitrate as a source of nitrogen in fertilizers 

 has been known for a long time, but it has been only in comparatively 

 recent years that it has been used on a very large scale. Formerly 

 the nitrogen in fertilizers was supplied mostly from guano, fish scrap, 

 leather scrap, and various other organic materials. The consump- 

 tion of sodium nitrate in fertilizers now exceeds by many times its 

 use for other purposes, and is rapidly increasing. The exhausted 

 soils of Europe and of some parts of the United States, as well as of 

 other countries, require year by year more fertilizing materials to 

 make up for what is taken away by excessive cultivation, and some 

 available compound containing nitrogen is one of the most important 

 of such materials. Sometimes nitrate is used alone in cases where a 

 nitrogenous compound is all that is needed, but more commonly it 

 is used in admixture with phosphates, potassium salts, and other 

 materials usually needed by depleted soils. 



NITRATE DEPOSITS ELSEWHERE THAN CHILE 



In parts of the world other than Chile, deposits of nitrates, espe- 

 cially potassium nitrate, and in smaller amounts calcium nitrate, have 

 been found in many places, but nowhere in quantities in any way 

 comparable with the sodium nitrate deposits of Chile, which today 

 supply most of the world's demand. In old times, however, before 

 this source became of commercial importance, potassium nitrate 

 was obtained in considerable quantities in India and other tropical 

 countries, where it occurs, often in association with calcium nitrate, 

 in the soil and the grounds surrounding dwellings. Nitrate was also 

 obtained in many parts of the world in caves, where it is found in 



