410 ELEMENTARY CHEMICAL MICROSCOPY 



EXPERIMENTS. 



a. Test for Fe in simple salts. 



b. Test in complex mixtures with other elements which will be precipitated by 

 K 4 Fe(CN) 6 . 



NICKEL. 



Crystal Forms and Optical Properties of Common Salts 

 of Nickel. 



A. ISOTROPIC. 



Ammonia nickel nitrate (I). 



B. ANISOTROPIC. 



Hexagonal. 



Tetragonal. 



Orthorhombic. — Sulphate. 



Monoclinic. — Acetate; chloride; nitrate; sulphate; 

 ammonium-nickel sulphate; potassium- 

 nickel sulphate. 



Triclinic. 



DETECTION. 



CH 3 - C = NOH 

 A. By Means of Dimethyl Glyoxime, I 



CH 3 - C = NOH 



To a drop of the solution to be tested add ammonium hydroxide 

 until in slight excess. Decant the solution of the hydroxides 

 which have been dissolved by the ammonium hydroxide, from 

 those which are insoluble. Close to the clear ammoniacal drop 

 place a large drop of a freshly prepared saturated solution of 

 dimethyl glyoxime. Cause the ammoniacal drop to flow into 

 the reagent. 



Nickel yields an immediate rose-pink or magenta-colored 

 precipitate — at first amorphous in character, later changing into 

 a felt of exceedingly fine acicular crystals. Near the edges of 

 the crystalline mass tiny needles form in star-like and irregular 

 bristling clusters. Often a yellow precipitate is first formed, 

 changing only slowly into pink. 



The nickel salt of dimethyl glyoxime has the formula 



