222 



THE POPULAR SCIENCE MONTHLY 



Photograph loaned by Mr. C. E. Atwood, Antofagasta, Chile. 



Nitrate in the cancha, being bagged and put on cars for shipment. 

 In the left background, a big accumulation of ripio. 



tallizing pans. The finished nitrate is shoveled from the bateas into 

 cars, drawn to the deposit, or canclia, and there after drying for several 

 days is bagged ready for shipment. Shipment in bulk is impracticable 

 because the nitrate so readily absorbs water. Even when shipped in 

 sacks it sometimes becomes caked in the holds of ships and has to be 

 taken out with picks. 



From the agua vieja, iodine is extracted by a simple process of pre- 

 cipitation with chemicals (mainly sodium sulphites). It figures only 

 as an important by-product of the industry, for the " iodine trust " 

 makes an annual allotment to each establishment, commonly less than 

 what could be made in a month, if there were no restrictions on 

 production. 



The .only other important step in the refining of nitrate is the clear- 

 ing and recharging of the boiling tanks. First, fresh water is run 

 through to take out what it will of the remaining nitrate, this water 

 being used subsequently, with aqua vieja, in the boiling process, for the 

 more nitrate in solution at the outset the easier it is to get a saturated 

 caldo. After the washing is over, a trap in the bottom of the tank is 

 opened and the waste, or ripio, is removed. This process is the most 

 bothersome in the industtw, because for each charge of 70 tons of caliche, 

 50 tons or more of ripio must be removed. It is very hard on the men 

 who work in the steaming hot tanks, and the disposal of the waste after 

 it is removed, not uncommonly 1,000 to 2,000 tons a day, soon comes 

 to be a problem. None of the operators succeed in getting much more 

 than 75 per cent, of the nitrate originally in the caliche, hence ripio 

 commonly contains 4 to 10 per cent, of nitrate, and the great piles con- 



