MICROCHEMICAL REACTIONS OF THE COMMON ACIDS 425 



of Benzidine Hydrochloride 1 by Method /, page 299. Light blue 

 prisms and stars will soon appear. 



Ferrocyanides do not give this reaction. 



c. Give no color with dilute solutions of pure Ferric Salts. 



FERROCYANIDES. 



a. Give a Blue Precipitate with Salts of Iron and a brown one 

 with salts of copper in acetic acid solution. 



b. With Quinoline Hydrochloride yield upon warming cubical 

 crystals. 



IODIDES. 



a. To a drop of solution add dilute sulphuric acid, a little 

 potato starch and a tiny fragment of ammonium persulphate. 

 The starch is turned blue or violet in the cold. See Bromides, 

 page 42 2. 



b. The silver nitrate precipitate is insoluble in ammonium 

 hydroxide; distinction from chloride and bromide. 



c. Yield characteristic hexagonal plates with lead nitrate. 

 See Lead, page 369. 



IODATES. 



a. Dissolve in water, add a very tiny drop of dilute sulphuric 

 acid, a little potato starch and finally a crystal fragment of 

 morphine sulphate. Iodine is set free and the starch granules 

 turn blue or violet. 



Iodides do not give this reaction; nor will iodates give reaction 

 a under iodides. 



NITRATES. 



a. With Nitron 2 Sulphate in Acetic Acid Solution. Apply the 

 reagent by Method 7, page 299. 



There is immediately formed a heavy precipitate, consisting 

 of masses of exceedingly minute needles. In a few seconds 



1 Behrens, Z. anal. Chem., 43, 423. 



2 " Nitron " is the usual name given to Diphenyl-endanilodihydrotriazol 



: N-N-CeHe. Nitron Sulphate = C^H^ H 2 SO 4 . 



I 



