298 



On Chemical Tests. 



[Oc 



nia may be detected hy holding a rod dipped in muriatic acid in the va- 

 pour. See 11, d. and 27 b. 



c Caustic potash p o luces, when added to an ammoniacal salt, the 

 odour of ammonia. This distinguishes these salts from other alkaline 

 salts. See 27, b. Chloride of platinum detects salts of ammonia by a 

 yellow precipitate of very small crystals, but as it acts also on salts of 

 potash, the one may be mistaken for the other, if the chloride of 

 platinum test, only, be employed. Ammoniacal salts are not precipita- 

 ted by infusion of nut galls, nor by prussiate of potash. 



d. If to an ammoniacal salt dissolved in water a little of any salt 

 containing magnesia be added, and afterwards phosphate of soda be 

 dropped in, a copious white precipitate falls. 



29- AMMOIIA, benzoate of, is an excellent test for separating iron 

 from manganese when together in one solution, which should be ac- 

 curately rendered neutral. It also liberates iron from all earthy 

 salts, and from nickel, cobalt, zinc and some other metals, 



30. AMMONIA, carbonate of, -detects copper, turning the solution 

 blue, when neutral. This test acts, generally speaking, like am- 

 monia. See table of re-agents. Carbonate of ammonia in its solid 

 state should be entirely volatilized by heat. It may contain impu- 

 rities, and may be examined in the same manner if used as a test 

 as carbonate of potash, see 98, d. 



31. AMMONIA, fluate of, detects lime, but the oxalate of ammo- 

 nia is a more common test, though Dr. Henry says, he finds the 

 fluate of ammonia to be the most delicate. 



32. AMMONIA^ ferrocyanate of, this tes': is of use only in the 

 analysis of saline substances. It may happen, for example, that a fluid 

 contains neutral salts with alkaline bases, together with metallic salts. 

 In this case ferrocyanate of potash cannot be well applied to separate 

 the metallic salts, because it then would be difficult to ascertain whether 

 the alkaline salts were originally present in the solution or not ; but if 

 ferrocyanate of ammonia be employed, no ambiguity can result; for the 

 metallic salts need only be precipitated by this test, and the earths by bi- 

 carbonate of ammonia, in a temperature of 180°, or upwards, in order to 

 ensure the decomposition of magnesian salts, which this carbonate does 

 not effect in the cold. The liquor may then be separated by filtration, 

 and boiled to dryness, and the dry mass exposed to such a heat as is 

 sr fficient to expel the ammoniacal salts. This application of heat will 



