72 



Soil Analysis 



[292 



vessel in which it is contained, and vigorously stirred, the 

 ammonium chloride will crystallise out in minute crystals. 

 These may be filtered off and dried. The result will be a fine 

 powder just suitable for our purpose. 



292. The Operation. — Weigh out about a gram of the 

 dry substance, as described in paragraph 285, and introduce 



it into a deep platinum 

 crucible, together with 

 a gram of dry NH 4 C1 

 and 6 grams of pure 

 dry CaC0 3 . Mix tho- 

 roughly with a stout 

 wire, brushing back all 

 adherent matter from 

 the wire to the crucible. 

 Cover the crucible, and 

 raise it to a red heat 

 over a Bunsen for an 

 hour. The heating is 

 best started by plac- 

 ing the crucible in an 

 inclined position (see 

 fig. 45) and heating the top of the crucible first, moving the 

 burner from time to time until the whole is at a red heat. At 

 the end of an hour place the crucible in a Fletcher muffle 

 furnace (fig. 17), and keep at a bright red heat for forty 

 minutes. 



Allow the crucible to cool. Place in a 12-oz. beaker and 

 slake the contents with hot water. They will rapidly break 

 up, and may be detached from the crucible with a wash bottle. 

 Remove the crucible with a glass rod and wash well, adding 

 the washings to the liquid in the beaker. Boil the liquid for 

 a few minutes. Decant through a filter. Wash three times 



Fig. 45. 



