412 ELEMENTARY CHEMICAL MICROSCOPY 



salts, such as (NH^SC^-FeSCU or 2 NH 4 Cl-FeCl 2 . Non- 

 volatile organic acids prevent the precipitation of ferric hydroxide 

 and the ferric salts thus remaining in solution will react with 

 the glyoxime. 



B. Other Tests for Nickel. 



1. Triple nitrite of lead nickel and potassium K 2 PbNi(NO2)6. 

 See Lead, Method C, page 373; Copper, Method B, page 386. 



2. Ammonium nickelous phosphate NH4N1PO4 6 H^O. See 

 Magnesium, Method B, page 350. This salt is isomorphous 

 with the magnesium salt. 



Note. The addition of hydrogen peroxide causes no change 

 in the color of the crystals of ammonium nickel phosphate, but 

 will turn those of cobalt brown. 



EXPERIMENTS. 



a. Try the glyoxime reaction on salts of Ni in NH 4 OH and in acid solution; and 

 in different concentrations. 



b. Try test upon Co compounds. 



c. Make a mixture of Ni and Co and test. 



d. Test for Ni in the presence of much Cu. 



Remove the Cu from a drop by means of metallic Zn and test again. Then try 

 the detection of Ni in the presence of much Fe. 



e. Apply the phosphate test to a Ni (ous) salt and as soon as the crystals are well 

 formed, allow a drop of H 2 O 2 to flow into the drop. Repeat the process with a 

 Co salt. 



COBALT. 



Crystal Forms and Optical Properties of Common Salts of 

 Cobalt. 



A. ISOTROPIC. 



B. ANISOTROPIC. 



Hexagonal. 

 Tetragonal. 

 Orthorhombic. - - Ammonium-cobalt phosphate; 



purpureo-chloride (pseudo tetragonal) . 

 Monoclinic. Acetate; chloride; luteo-chloride; 



nitrate; potassium-cobalt sulphate; roseo- 



chloride ; sulphate. 

 Triclinic. 



