IRON. 



173 



Analytical reactions. 



1. Ammonium sul- 

 phide. 



2. HydrosulpTiuric 

 acid. 



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. 



. Potassium sul- 

 phocyanate. 

 KCNS. 



Ferrous salts. 



(Use FeSO 4 .) 



Black precipitate of ferrous 

 sulphide (Plate I., 1). 

 FeS0 4 +(NH 4 ) 2 S = 



(NH 4 ) 2 S0 4 



No change. 



White precipitate of ferrous 

 hydroxide soon turning 

 green, black, and brown. 

 Precipitation not complete 

 (Plate I., 2). 



FeCl 2 4- 2NaOH = 

 2NaCl+ Fe(OH) 2 . 



White precipitate of ferrous 

 carbonate, soon turning 

 darker. 



2NaCl + FeCO 3 . 



Almost white precipitate, soon 

 turning darker. 



Almost white precipitate, soon 

 turning blue by absorption 

 of oxygen (Plate I., 4). 



Blue precipitate of ferrous ferri 



cyanide, or TurnbulFs blue. 



3FeCl 2 4- K 6 Fe 2 (CN) 12 = 



6KC1 4- Fe 3 Fe 2 (CN) 12 . 



No change, provided oxidation 

 of the ferrous salt has not 

 taken place. 



As above. 



Ferric salts. 



(Use Fe 2 Cl 6 .) 



Black precipitate of ferrous sul- 

 phide mixed with sulphur. 

 Fe 2 Cl 6 + 3[(NH 4 ) 2 S] = 

 6NH 4 C1 4- 2FeS 4 S. 



Ferric salts are converted into 

 ferrous salts with precipita- 

 tion of sulphur. 



Fe 2 Cl 6 4- H 2 S = 

 2FeCl 2 + 2HC1 + S. 



Reddish-brown precipitate of 

 ferric hydroxide Precipita- 

 tion is complete (Plate 1 , 3). 

 Fe 2 Cl 6 4- 6(NH 4 OH) = 

 6NH 4 Cl4-Fe 2 (OH) 6 . 



Reddish-brown precipitate of 

 ferric hydroxide, with libera- 

 tion of carbon dioxide (Plate 

 I, 3). 

 Fe 2 Cl 6 + SNa^COg + 3H 2 O = 



6NaCl 4 Fe 2 (OH) 6 + 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). 



2Fe 2 Cl 6 + 3[K 4 Fe(CNj 6 ] = 

 12KC1 4- Fe 4 3[Fe(CN) 6 ]. 



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 (Plate VII., 3). 



Deep blood-red precipitate of 

 ferric sulphocyanate (Plate I., 

 6.) 



