IRON. 



301 



Tests for iron. 



1. Ammonium sul- 

 phide. 



2. Hydrogen sul- 

 phide. 



3. Ammonium, so- 

 dium, or potas- 

 sium hydroxide 



4. Ammonium, so- 

 dium, or potas- 

 sium carbonate. 



5. Alkali phosphates 



or arsenates 



6. Potassium ferro- 



cyanide. 



K 4 Fe(CN) 6 . 



7. Potassium ferri- 



cyanide. 



K 6 Fe 2 (CN) 12 . 



8. Tannic acid. 



9 Potassium sul- 

 phocyanate. 

 KCNS. 



Ferrous salts. 



(Use FeSO 4 .) 



Black precipitate of ferrous 

 sulphide (Plate I., 1). 

 FeSO 4 + (NH 4 ) 2 S = 

 (NH 4 ) 2 SO 4 + FeS. 



No change, except sometimes 

 a slight black discoloration, 

 due to the formation of a 

 trace of FeS. . 



White precipitate of ferrous 

 hydroxide soon turning 

 green, black, and brown. 

 Precipitation not complete 

 (Plate I., 2). 



2NaCl+ Fe(OH) 2 . 



White precipitate of ferrous 

 carbonate, soon turning 

 darker. 



FeCl 2 + Na 2 CO 8 = 

 2NaCl 4- FeCO 3 . 



Almost white precipitate, soon 

 turning darker. 



Almost white precipitate, 

 K 2 Fe[Fe(CN) 6 ], soon turning 

 blue by absorption of oxygen 

 (Plate I., 4). 



Blue precipitate of ferrous ferri- 



cyanide, or Turnbull's blue. 



3FeCl 2 + K 6 Fe 2 (CN) 12 = 



6KC1 + Fe 8 Fe a (CN) lr 



No change, provided oxidation 

 of the ferrous salt has not 

 taken place. 



As above. 



Ferric taltt. 



(UseFeCl,.) 



Black precipitate of ferrous sul- 

 phide mixed with sulphur. 

 2FeCl 3 + 3[(NH 4 ) 2 S]= 

 6NH 4 C1 + 2FeS + S. 



Ferric salts are converted into 

 ferrous salts with precipita- 

 tion of sulphur. 



2FeCl. 2 + 2HCl-f S.. 



Keddish-brown precipitate of 

 ferric hydroxide. Precipita- 

 tion is complete (Plate I., 3). 

 3(NH 4 OH) = 

 Fe(OH) 3 : 



Reddish-brown precipitate of 

 ferric hydroxide, with libera- 

 tion of carbon dioxide (Plate 

 I., 3). 



2FeCl 3 -f 3Na 2 CO 3 + 3H,O - 

 GNaCl + 2Fe(OH) 8 + 3CO 2 . 



A yellowish-white precipitate 

 is produced. 



Dark-blue precipitate of ferric 

 ferrocyanide, or Prussian blue. 

 Decomposed by alkalies ; in- 

 soluble in acids (Plate I., 5). 

 3[K 4 Fe(CN) 6 ] = 

 Fe 4 3[Fe(CN) fl ]. 



No precipitate is produced, but 

 the liquid is darkened to a 

 greenish-brown hue. 



A dark greenish-black precipi- 

 tate of ferric tannate is pro- 

 duced. 



Deep blood-red solution of fer- 

 ric sulphocyanate, Fe(CNS) 3 

 (Plate I., 6). 



