58 

 PRACTICE 26. (Con't.) 



tion to be made by the instructor so that i cc. shall be equivalent to 

 2 mg. of iron). 



cc. KMnO 4 used 



Percent Fe 



Average 



(f) Aluminum. 



Heat to boiling 100 cc. of Solution A in a 250 cc. beaker, add ammo- 

 nium hydroxid carefully, until an odor of ammonia is distinguishable after 

 blowing into the beaker, let settle, and decant supernatant liquid through 

 an ii cm. filter. Wash with about 50 cc. of hot water by decantation, dis- 

 solve in hydrochloric acid, dilute to 100 cc., heat to boiling, and again pre- 

 cipitate by adding ammonium hydroxid as above. Decant through the 

 same filter, transfer to the filter, and wash with hot water until free of chlo- 

 rids. Dry and ignite in a weighed crucible over a Bunsen burner. 



Weight of crucible plus A1 2 O 3 , Fe 2 O 3 , P 2 O 5 



Weight of crucible 



Weight of A1 2 O 3 , Fe 2 O 8 , P 2 O 6 



Weight Fe 2 O 3 and P 2 O 5 (computed) 



Weight of A1 2 O 3 



Weight Al 



Percent Al 



Average 



(g) Calcium, 



Concentrate the filtrate from (f) to 50 cc., add a few drops of ammo- 

 nium hydroxid and then ammonium oxalate until all the calcium is pre- 

 cipitated. 



Digest on the water-bath 2 hours, filter through a 9 cm. filter, wash 

 with hot water until free of chlorids, dry, and ignite in a weighed crucible 

 over a Bunsen burner, finishing to constant weight over the blast lamp. 



Weight of crucible plus CaO 



Weight of crucible 



Weight of CaO 



Weight of Ca 



Percent Ca 



Average % 



(h) Magnesium. 



Concentrate the filtrate from (g) to 50 cc., cool, add a few drops of 

 ammonium hydroxid, then add slowly while stirring disodium phosphate 

 solution until the magnesium is all precipitated, add 10 cc. of ammonium 

 hydroxid, cover, and let stand over night. Filter through a 9 cm. filter, 

 wash with dilute ammonium hydroxid (l liter of ammonium hydroxid of 

 .96 sp. gr. diluted to 5 liters), dry, and ignite in a weighed crucible over a 

 Bunsen burner, finishing to constant weight over the blast lamp. 



