128 METALS AND THEIR COMBINATIONS. 



Both substances, the ammonium hydrogen sulphide and am- 

 monium sulphide, are valuable reagents, frequently used for the 

 precipitation of certain heavy metals, or for dissolving certain 

 metallic sulphides. 



Analytical reactions. 



1. All compounds of ammonium are volatilized by heating 

 upon platinum foil. 



2. All compounds of ammonium evolve, when heated with 

 the hydrates of calcium, potassium, or sodium, ammonia gas, 

 which may be recognized by its odor, or by its action on paper 

 moistened with solution of cupric sulphate, which is thereby 

 colored dark blue. 



3. Add to solution of ammonium salt some platinum chloride 

 and a few drops of hydrochloric acid; a yellow precipitate of 

 ammonium platinum chloride, (NH 4 Cl) 2 PtCl 4 , is produced. 



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

 water. 



QUESTIONS. 



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



202. Is ammonium known Jn the separate state ? 



203. What is ammonium-amalgam, how is it obtained, and what are 

 its properties ? 



204. What is the source of ammonium compounds ? 



205. State the composition, mode of preparation, and properties of 

 sal-ammoniac. 



206. How is ammonium carbonate manufactured, and what difference 

 exists between the solid article and its solution ? 



207. State the composition of ammonium sulphide and of ammonium 

 hydrogen sulphide ; how are they made, and what are they used for? 



208. By what processes may ammonium sulphate, nitrate, and phos- 

 phate be obtained from ammonium hydrate or ammonium carbonate, 

 and what chemical change takes place ? 



209. How does heat act upon ammonium compounds ? 



210. Give analytical reactions for ammonium salts. 



