220 CHEMISTBY. 



The alkaline gas ammonia is composed, you remember, of 

 hydrogen and nitrogen, or is NH 3 . Now a solution of this 

 gas in water acts like the hydrate of an alkaline metal, 

 combining with acids to form crystallizable salts. This 

 analogy has caused chemists to conjecture that, since NH 3 -f 

 H 2 O is the same as NH 4 HO, there is a metal NH 4 , of which 

 NH 4 HO is the true hydrate, just as KHO is the hydrate of 

 potassium. This compound metal reminds us of cyanogen, 

 which, you remember, was a compound also, and was called 

 a radical. 



Note that if there be an ammoniacal metal, it is not an element, as all 

 other metals are, but a compound. It is composed of nitrogen and hydro- 

 gen, just as is the ammoniacal gas, and it differs in composition from this 

 gas only in having one third more hydrogen in it. Though no one has 

 ever succeeded in obtaining this metal, all chemists seem to believe in its 

 existence. The evidence on which this belief is based is twofold. First, 

 the salts of ammonia are so much like other salts that have a metallic base 

 that it would be a very strange thing if they did not also have such a base. 

 Thus in sal ammoniac we have a salt so similar to other salts that we 

 should expect to find, as we do in them, that one of the constituents is a metal. 

 But it is composed of three gases chlorine, nitrogen, and hydrogen. It is 

 supposed, therefore, that as common salt is composed of chlorine and the 

 metal sodium, so this salt is composed of chlorine and a metal ammonium, 

 the nitrogen and hydrogen being so combined as to act in this latter capac- 

 ity. But by whatever method the chemist separates the chlorine from this 

 combination, the metal eludes his grasp, and he gets only nitrogen and hy- 

 drogen, each by itself. The evidence, therefore, that there is a metal here 

 is incomplete. But there is, secondly, another proof of a more decided 

 character. If sal ammoniac that is, chloride of ammonium be mixed with 

 an amalgam of mercury and sodium, a change takes place resulting in the 

 formation of common salt, or chloride of sodium, and an amalgam different 

 from that which was put into the mixture. How is this ? The sodium has 

 left the mercury to unite with the chlorine of the sal ammoniac. What has 

 taken its place in the amalgam? Something from the sal ammoniac, and 

 that something must be a metal, for nothing but a metal has ever been 

 known to form an amalgam with mercury. The proof, therefore, is quite 

 decided that sal ammoniac is a chloride of a metal, and therefore its proper 

 name is chloride of ammonium. 



