165-173] TESTS FOR THE METALS 57 



165. Potassium Ferricyanide, K 3 Fe(CN) 6 , gives 

 a dark-blue precipitate, soluble in HC1. 



166. Potassium Sulphocyanide (KCNS) produces 

 no change in ferrous solutions if free from ferric salts. 



FERRIC SALTS.— Use ferric chloride (FeCl) 3 . 



167. Ammonium Hydrate (NH 4 OH) or Potas- 

 sium Hydrate (KHO) gives a reddish-brown flocculent 

 precipitate of ferric hydrate, Fe(OH) 3 , soluble in hydro- 

 chloric acid (HC1), insoluble in excess of AmHO and KHO. 



168. Ammonium Sulphide, (NH 4 ) 2 S, gives a black 

 precipitate of ferrous sulphide (FeS), which contains white 

 sulphur (S). The black FeS hides the white S from view. 



169. Potassium Ferrocyanide, K 4 Fe(CN) 6 , gives 

 a dark-blue precipitate of Prussian blue, soluble in oxalic 

 acid, turned brown by potassium hydrate (KHO). 



170. Potassium Ferricyanide, K 3 Fe(CN) 6 , gives 

 no precipitate, but the liquid darkens in colour. 



171. Potassium Sulphocyanide (KCNS) gives a 

 blood-red coloration, which may be destroyed by the addi- 

 tion of mercuric chloride (HgCl 2 ). 



172. By heating a small portion of solid ferric or 

 ferrous salt on the borax bead (27) in the outer blowpipe 

 flame a reddish-brown colour is obtained whilst the bead is 

 hot, which fades on cooling. The inner flame gives an 

 olive-green bead both hot and cold. 



MANGANESE (Mn).— Use manganous sulphate 

 (MnS0 4 ) solution. 



173. Ammonium Hydrate (NH 4 OH) gives a white 

 precipitate of manganous hydrate, Mn(OH) 2 , which quickly 



