/ 



i 



,J 



anti 



Chemical Powers of Ammoniacal Salts. 259 



In all these examples (and no doubt many other similar ones exist) 

 it is easy to perceive that the nitric acid, of the ammoniacal salt, takes 

 possession of the fixed base, potassa, while the different acids, ferro- 

 cyanic, chromic and liydryodic, incapable of resisting the further 

 power of the acid salt, speedily suffer decomposition. Hence the 

 effects are extremely analogous to those of strong nitric acid, but 

 other examples are not always as satisfactory. Thus, with respect 

 to the metals, it is not easy to explain why the fused nitrate should 

 have no action whatever upon pure tin and iron, when we consider 

 how very rapidly these bodies are oxidated in the free acid. Per- 

 haps the difference is owing to the absence of water from the fused 

 salt. Mercury and arsenic also appear capable of resisting the ac- 

 tion of tlie ammoniacal nitrate. Upon silver, copper, bismuth, 

 mony and nickel, if heat be constantly applied, it readily effects ox- 

 idation, but the metals which best illustrate its oxidating and solvent 

 powers, are zinc and lead. The zinc disappears with as much ra- 

 pidity as when exposed to the strongest mineral acids and, at the same 

 time, so completely sustains tlie requisite temperature, tliat it becomes 

 unnecessary to continue the application of heat; after the action com- 

 mences. 



During this very turbulent operation, nitrogen gas, ammonia and 

 water, are given off in abundance. A mercurial thermometer indi- 

 cated that the nitrate is decomposed by zinc at 280^ or 300° Fah. 

 (temperatures a little above its point of fusion,) but the heat liberated, 

 even By small pieces of the metal, was so great as to indicate 540^ 

 in a very short time. The most remarkable circumstance attending 

 this decomposition, and which appears inconsistent with the usual pro- 

 ducts of nitrate of ammonia when exposed to an elevated tempera- 

 ture, is, that no protoxide of nitrogen, or nitric oxide, could be detect- 

 ed in the gas collected over water. Indeed I am convinced, from 

 several experiments, that this decomposition furnishes pure nitrogen 

 as conveniently as that of any other process known to chemists, and 

 as such I will here venture to recommend it. 



The following method was found most convenlent. 



A tubulated retort is to be partly filled with the nitrate of ammonia, 

 and a cork fitted to the tubulature. Through this cork is to pass, 

 fi'eely, either a knitting needle or an iron wire, holding, by means of 

 I a hook, the coil of zinc. As soon as the salt has entered into fusion, 



the knitdng needle must be pushed down .far enough to place the 

 zmc in contact with the nitrate. This arrangement is not only con- 

 venient but necessary, for, If the zinc be thrown at once into the fu- 



C-ii I 





