8 4 



CHEMICAL FERTILIZERS 



avoid distillation are completely out of date. Fig. 2 

 shows a typical plant for the preparation of ammonium 

 sulphate from ammonia liquor. The liquor first enters 



FIG. 2. Sulphate of ammonia still. 



L indicates the place where lime is added ; by the side is a grid to 

 prevent large particles of lime blocking the pipes. 



S indicates several steam pipes which admit steam (i) into the lime 

 tank to make milk of lime ; (2) to the two stills to expel ammonia 

 from solution ; (3) to the ejector which blows the finished sulphate 

 of ammonia from the saturator to the storage box. 



P indicates the piston of the pump which forces the milk of lime into the 

 lower portion of the still. The two valves which convert the oscil- 

 latory movement of the piston into a unidirectional flow of fluid 

 are not shown in the diagram. 



A indicates the point at which ammonia liquor enters. 



H is the heater in which the waste heat from the saturator heats the 

 ammonia liquor to near the boiling temperature. After being heated 

 the ammonia liquor flows to the first still where steam drives out 

 the ammonia gas. By flowing over a series of trays a gradual 

 fractionation takes place. _ 



B indicates the lower or lime portion of the main still. 



D indicates the second still for distilling the " fixed ammonia." Between 

 the two stills a wide pipe permits steam to pass one way and liquor 

 in the opposite direction. 



K is the head of the main still and prevents priming. 



C is a lead coil from which the ammonia gas enters the saturator. 



V is the point at which the vitriol is added. In practice a steady stream 

 of acid can be maintained. 



E 



Z 



G is a gutter which returns the mother liquor to the saturator. 



W is the exit for waste iime. 



is the ejector of the sulphate of ammonia, 

 is the store of finished sulphate of ammonia. 



a heat interchanger, by which means the ammonia liquor 

 is heated to somewhere near boiling point, but in small works 



