1SS9] 



On Chemical Tests. 



297 



27. AMMONIA, detects copper, turning the solution blue. Am- 

 monia acts on a great number of the metals. See table of re-agents. It 

 is defected by muriatic acid, see 11, d. Pure liquid ammonia is liable to 

 attract carbonic acid from the atmosphere, bnt this acid may be detected 

 by baryta, see 40, or lime water, see ~5. 



a. Ammonia is acted on by a spirituous solution of chloride of pla- 

 tinum, and by suiphafe of alumina in the same manner as potash is, 

 namely, the former produces a bright yellow precipitate, and the latter 

 produces crystals of alum, if the solution be acid, and concentrated. 

 Tartaric acid produces in concentrated solutions of ammonia a crystal- 

 line precipitate of <l)i tartrate of ammonia. Hydrofluosilicic acid preci- 

 pitates its own silica in solutions of ammonia, but it must not be add" 

 ed to saturation, the ammonia must be in excess,otherwise no precipitate 

 is produced. 



b. When dry ammoniacal salts or concentrated solutions of them ; and 

 caustic or carbonated alkalies, or earths are triturated together, an imme- 

 diate odour of ammonia escapes ; and the presence of ammonia is infaMi* 

 bly detected by presenting to the mass, or the liquid, a rod dipped in rather 

 strong, bid not fuming muriatic acid. 



c. it is of the greatest importance to be aware of the remarkable pi 

 perty possessed by ammonia of forming triple salts with earths and 

 metallic oxides, as is the case when the sulphates of magnesia, lime, 

 and iron, occur together. 



d. If a mineral water contain free carbonic acid, or carbonate of mag. 

 nesia, and carbonate of lime, the addition of ammonia will take up part 

 of the carbonic acid, and the carbonate of ammonia thus formed will 

 throw down carbonate of lime. 



e. ' Liquid ammonia dissolves several of the metallic oxides, and with 

 some of them forms crystallizable compounds. It dissolves the oxides 

 of silver, copper, zinc, arsenic, antimony and tellurium: the protoxides 

 of iron, cobalt, and nickel ; and the peroxides of tin, mercury, gold, and 

 palladium. These compounds are all decomposed by heat. The com- 

 pounds of ammonia with the oxides of gold, silver, and platinum deto- 

 nate when heated, and the oxide and ammonia are both decomposed. 



28. AMMONIA, salts of, are detected, (a) by corrosive subli- 

 mate; (6), by heat; (c), by caustic potash, and some other tests. 



a. To a neutral solution of an ammoniacal salt, add a drop of any alka- 

 li; the solution of corrosive sublimate or perchloride of mercury then 

 added, becomes a delicate test for ammonia by producing a while pre- 

 cipitate. 



b. Heat liberates the ammonia in an ammoniacal salt, and the ammo- 



