AMMONIUM. 



149 



Analytical reactions. 

 (Ammonium chloride, NH 4 C1, may be used.) 



1. All compounds of ammonium are volatilized by heating to a low 

 red heat. 



2. All compounds of ammonium evolve ammonia gas when heated 

 with hydroxide of calcium, potassium, or sodium. The ammonia may 

 be recognized by its odor, or by its action on paper moistened with 

 solution of cupric sulphate, which is thereby colored dark-blue, or by 

 causing the appearance of dense white fumes of ammonium chloride, 

 upon holding a glass rod, moistened with hydrochloric acid, in the 

 gas. 



3. Add to solution of ammonium salt some platinic chloride, a few 

 drops of hydrochloric acid, and some alcohol ; a yellow precipitate 

 of ammonium platinic chloride, (NH 4 Cl) 2 PtCl 4 , is produced. See 

 explanation of the corresponding potassium reaction on page 140. 



4. The addition of sodium cobaltic nitrite causes in neutral or 

 acid solutions a yellow precipitate of ammonium cobaltic nitrite, 

 (NH 1 N0 2 ) 6 .Co 2 .(N0 2 ) 6 . 



5. Ammonium salts are colorless, and (almost all) soluble in water. 

 Traces of ammonium compounds may be detected by alkaline mer- 

 curic-potassium iodide (Nessler's solution), which causes a reddish- 

 brown precipitate or coloration. 



Summary of analytical characters of the alkali-metals. 



QUESTIONS. 201. What is ammonium, and why is it classed with the alkali- 

 metals? 202. Is ammonium known in a separate state? 203. What is ammo- 

 nium-amalgam, how is it obtained, and what are its properties ? 204 What is 



