MICROCHEMICAL REACTIONS OF THE COMMON ACIDS 425 
of Benzidine Hydrochloride'^ by Method I, 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. 
h. 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 422. 
h. 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. 
lODATES. 
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^ Sulphate in Acetic Acid Solution. Apply the 
reagent by Method I, page 299. 
There is immediately formed a heavy precipitate, consisting 
of masses of exceedingly minute needles. In a few seconds 
^ Behrens, Z. anal. Chem., 43 , 423. 
* “ Nitron ” is the usual name given to Diphenyl-endanilodihydrotriazol 
: N-N-CeHs. Nitron Sulphate = C1.0H16N4 • H2SO4. 
j \N(C6H6)/ I 
