AMMONIUM. 271 



ing to a solution of the hydrosulphide, prepared as above, an equiva- 

 lent amount of ammonia water. 



These solutions can easily be freed from the sulphide by boiling. Both sub- 

 stances, the ammonium hydrogen sulphide and ammonium sulphide, are valu- 

 able reagents, frequently used for precipitation of certain heavy metals, or for 

 dissolving certain metallic sulphides. (See under Hydrogen Sulphide.). 



Tests for ammonium compounds. 



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



1. Ammonium salts give the same form of precipitates as potas- 

 sium with solution of platinic chloride, sodium cobaltic nitrite, and 

 tartaric acid (see tests for potassium). 



2. All compounds of ammonium are volatilized below or at a low 

 red heat, either with or without decomposition (see preparation of 

 nitrogen and nitrogen monoxide in chapter on Nitrogen). If the 

 acid constituent of the salt is volatile and not decomposed by heat, 

 the salt volatilizes without decomposition. 



Heat with a small flame a little ammonium chloride in a covered 

 porcelain crucible. The salt sublimes upon the sides and cover of 

 the crucible. 



3. The best test and one which is sufficient for recognition of any 

 ammonium compound is to heat a mixture of it and slaked lime or 

 strong alkali in a tube. Ammonia gas is liberated, which may be 

 recognized by its odor and action on red litmus-paper, and by causing 

 dense white fumes when a rod, moistened with strong hydrochloric 

 acid, is held in the mouth of the tube. 



All commonly occurring ammonium salts are colorless, soluble in 

 water, and odorless, with the exception of the carbonate and sulphide. 

 Traces of ammonium compounds are detected by Nessler's 



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

 metals? Is ammonium known in a separate state? What is ammonium- 

 amalgam, how is it obtained, and what are its properties? What is the source 

 of ammonium compounds? State the composition, mode of preparation, and 

 properties of sal ammoniac. How is ammonium carbonate manufactured, and 

 what difference exists between the solid article and its solution ? State the 

 composition of ammonium sulphide and of ammonium hydrogen sulphide ; 

 how are they made, and what are they used for? By what process may ammo- 

 nium sulphate, nitrate, and phosphate be obtained from ammonium hydroxide 

 or ammonium carbonate, and what chemical change takes place ? How does 

 heat act upon ammonium compounds? Give analytical reactions for ammo- 

 nium salts. 



