92 MANUFACTURE OF FERTILIZING MATERIALS 



three to four days. The steam given off contains 

 an important amount of iodine which can be 

 avoided by an addition of soda. 



3 Vessels Heated by a Closed Tubular Bundle 

 or Steam Coil. This method has been introduced 

 by British and German companies. These vessels 

 measure 36 ft. long, 6 ft. wide by 6 ft. high, into 

 which the mother liquor and the wash water are 

 run and heated to boiling. Then six trucks of 

 perforated wrought iron containing about four tons 

 of caliche are run in. The nitrate dissolves in 

 the water while the residue remains in the trucks. 

 To hasten solution the liquid is agitated by in- 

 jection of steam and of hot air under the truck 

 by means of a Koerting's injector. This plan 

 works more economically than the preceding 

 one. At the same time the solutions so obtained 

 are purer and more concentrated. To get a 

 ton of nitrate requires three tons of caliche. 

 The crystallized nitrate is left to drain, then it 

 is dried in the open air. Nevertheless it always 

 remains slightly moist owing to the presence 

 of chlorides of calcium, of magnesium, and pos- 

 sibly also of nitrates of calcium and magnesium, 

 It crystallizes in rhombohedra, and has a dirty 

 reddish gray appearance, due to its oxide of iron 

 content and to bituminous substances. The 

 residue left by the solution still contains from 

 15 to 35 per cent of NaNOs. It is boiled with 

 water and a weak solution of 43 to 45 B. ob- 

 tained, which is utilized to dissolve a fresh 



