144 MANUFACTURE OF FERTILIZING MATERIALS 



water), heat on water-bath with beaker covered 

 until in solution, then determine iron with po- 

 tassium permanganate by volumetric method, 

 and from these results and total, iron and alu- 

 minium phosphate estimate the amount of iron 

 and alumina. 



Manganese. The filtrate above is concentrated 

 to about 100 cc., ammonia added to alkalinity, 

 bromine water added and the solution heated 

 to boiling. Allow the solution to cool and 

 add more bromine water and ammonia, and 

 heat as before to precipitate all the mangan- 

 ese; acidify with acetic acid, and filter while 

 still boiling, wash with hot water and ignite 

 as manganous manganic ioxide, Mn 3 O 4 . 



Calcium. Evaporate above filtrate to about 

 50 cc., add ammonia to slight alkalinity, and to 

 the hot solution add ammonium oxalate and 

 allow to stand twelve hours, filter, and wash with 

 hot water containing a little ammonia; dry, 

 and transfer precipitate to tared platinum cru- 

 cible; burn filter-paper, add ash to the crucible, 

 and ignite, at first slowly and finally with full 

 blast; cool, and weight as calcium oxide. 



Magnesia. If necessary concentrate the fil- 

 trate above, make alkaline with ammonia, 

 add Na2HPO4 until no further precipitate occurs, 

 stir carefully without touching sides of beaker, 

 and allow to stand until solution above precipi- 

 tate is perfectly clear. Filter and wash out 

 beaker with portions of the filtrate, and then 



