INORGANIC NITROGEN FERTILIZERS 95 



contains fresh caliche. In this last tank the fresh caliche 

 is boiled for two or three hours, the temperature rising to 

 112 C. (234 F.). In all, the caliche receives four or five 

 washes. The strong liquor from the fresh caliche then 

 flows into settling tanks, where mud deposits, the deposition 

 of which may be hastened by the addition of some precipi- 

 tating agent. The liquor then flows into crystallizing 

 tanks, which are about 15 ft. by 15 ft. by 2 ft. or 3 ft. 

 deep, with the bottom somewhat sloping. The liquors are 

 left to cool and crystallize for ten or fourteen days. The 

 nitrate, after draining, contains from about 8 to 10% of liquor. 

 The crystals, with their adhering mother liquor, are left 

 to dry in the air, whilst the mother liquor is returned to the 

 cistern for further working up. By exposure to air the 

 crystals dry until the moisture is reduced to 2-3 %, 

 when they are broken up with wooden mallets. 



The details of the process of heating and boiling caliche 

 depend on the facts that sodium nitrate is much more 

 soluble in hot water than in cold, and that sodium chloride 

 is equally soluble in either. A considerable amount of heat 

 is needed to bring the water up to boiling point. At first 

 cold water dissolves a large quantity of common salt as well 

 as other salts, but as more nitrate is added and goes into 

 solution the common salt is precipitated. This fine salt 

 coats the large pieces of caliche, and interferes with the 

 leaching out of the nitrate. The resulting nitrate of soda 

 has the composition shown in Table n. 



TABLE ii. 

 COMPOSITION OF NITRATE OF SODA. 



Several details need consideration before designing any 

 improvement in the method. The size of the lumps of the 



