PRODUCTION AND AGRICULTURAL USE OF SODIUM NITRATE 3 



then evaporated, to crystallize out the nitrate. Additional sodium 

 carbonate may also be treated directly with nitric acid, to increase the 

 output if desired. 



Sodium nitrate is also produced at some plants that employ the 

 synthetic ammonia process for fixing atmospheric nitrogen. At such 

 plants, one of which is located in the United States, the ammonia is 

 oxidized to form oxides of nitrogen which are then used to produce 

 sodium nitrate in the manner just described. The nitrite solution 

 formed by absorption of the oxides of nitrogen in the alkali towers may 

 be treated with higher oxides of nitrogen, instead of with nitric acid, 

 to convert the sodium nitrite to sodium nitrate. The production of 

 synthetic sodium nitrate on a commercial scale by this method com- 

 menced in this country in 1929. The sodium carbonate employed in 

 the process is manufactured from sodium chloride (common salt). 



A procedure has been very recently introduced in Norway in which 

 limestone is first treated with nitric acid to form a solution of calcium 

 nitrate which is then passed through a sodium zeolite to obtain a 

 sodium nitrate solution, the sodium zeolite being simultaneously con- 

 verted into calcium zeolite. The calcium zeolite is reconverted into 

 the sodium zeolite for reuse by passing sea water through it. In this 

 process, the comparatively cheap naturally occurring materials, 

 limestone and sea water, are used instead of the manufactured sodium 

 carbonate required in the above-mentioned procedures. Another 

 method that avoids the use of sodium carbonate was introduced in 

 this country during 1936. In this process, sodium chloride is treated 

 directly with nitric acid obtained from the oxidation of ammonia for 

 the production of sodium nitrate. 



Sodium nitrate is used for the manufacture of potassium nitrate, 

 explosives, glass, sodium nitrite, nitric acid, and other chemical prod- 

 ucts and for curing meat, but its principal use is as a fertilizer material. 



Although statistics on the total domestic production of synthetic 

 sodium nitrate are unavailable, exports (none prior to 1930) amounted 

 to 28,630 tons in 1930, 73,700 tons in 1931, 185,000 tons in 1932, 

 102,000 tons in 1933, 177,000 tons in 1934, and 153,000 tons in 1935. 

 Imports of sodium nitrate into this country, from 1916 to 1935 

 inclusive, are given in the following tabulation: 



Year 

 1916____ 



Short tons 

 1, 364, 463 



1917 __. 



_ 1, 728, 399 



1918 



______ 2, 066, 615 



1919 



456, 354 



1920 



1,480, 519 



1921 



413, 474 



1922 



607, 560 



1923 



998, 680 



1924 



_ 1, 105, 001 



1925 



1,245,693 



Year Short tons 



1926 1, 024, 014 



1927 838, 636 



1928 1, 156,860 



1929 1, 042, 113 



1930 636, 825 



1931 616, 687 



1932 56,482 



1933 137, 610 



1934 328, 750 



1935 437, 635 



COMPOSITION 



The composition of commercial sodium nitrate varies somewhat 

 according to whether it is of natural or synthetic origin. The composi- 

 tion of the natural, or Chilean, nitrate is also dependent upon whether 

 the Shanks or Guggenheim process -was used in its recovery. Chilean 

 nitrate produced by the Shanks process usually contains about 1 per- 

 cent of moisture and 0.2 percent of water-insoluble matter. The 



