THE NITRATE FIELDS OF CHILE 



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The crystallizing tanks. Refined nitrate in the tanks in the foreground : 

 tanks recently filled with caldo in the background. 



tanks, known as cliulladores, where the use of wheat flour, stable manure, 

 or other substances, causes the precipitation of the miscellaneous soluble 

 impurities, except ordinary salt, which have been dissolved out with the 

 nitrate. From this purification process the solution goes to the crys- 

 tallizing tanks, or bateas, which are placed ten or twelve feet above the 

 ground to permit free circulation of air and promote cooling and evapo- 

 ration. Thus dryness which figures in the origin and preservation of 

 the caliche also has an equally great value in the process of manufac- 

 ture. As the solution cools and the water evaporates, the nitrate begins 

 to crystallize on the surface, so a " stirring boy," or rayandero, is 

 employed to break up the film and make it settle. Five or six days are 

 necessary to complete the crystallizing process. A large plant may 

 have 300 or more bateas, capable of holding more than 1,000,000 gallons 

 of caldo, and yielding at each full charge as much as 2,500 tons of 

 nitrate. 



When crystallization has gone as far as it will, a valve in the bottom 

 of the batea is opened and the liquid is drawn off, leaving behind a thick 

 layer of glistening white crystals. This is the nitrate or salitre of 

 commerce, being 95 per cent, or more of pure nitrate of soda; the 

 remainder is largely water and salt. The liquid which is drawn off, 

 known as agua vieja, or mother liquor, still contains a large amount of 

 nitrate in solution, and is used over and over again in the boiling tanks. 

 In fact, no water is ever thrown away, the only loss being that which 

 passes into steam from the boiling tanks and evaporates from the crys- 



