COMPOSITION OF AMMONIUM AMALGAM. 179 



I think that from these experiments I am warranted in 

 drawing the two following conclusions, viz. : — 



i. In the fact of the gases being evolved in atomic pro- 

 portions, we have the clearest proof that the ammonia and 

 hydrogen are chemically combined. 



2. The compressibility of the mass proves that the 

 enlarged volume or swelling up is due mainly, if not 

 entirely, to free gases entangled in it. 



In connexion with the first of these conclusions arises 

 the further question whether the NH 4 is combined with 

 the mercury. That it is so combined appears in the highest 

 degree probable from the apparently uniform diffusion of 

 the NH 4 throughout the mass, and from the fact that such 

 a union would be only one additional instance of the innu- 

 merable cases in which this radical plays the part of a 

 metal. Seely says that, if the radical NH 4 be contained 

 in the amalgam at all, it must be in the state of gas. But 

 the figures furnished by my fifth experiment show that, if 

 this supposed NH 4 gas had the normal molecular volume, 

 and existed in the amalgam from the beginning, a force of 

 two atmospheres would be required to compress it within 

 the amalgam. The decomposition therefore is progressive, 

 and points to the existence of a real compound of NH 4 

 with the mercury. We may therefore admit that such a 

 compound is originally formed, and decomposes rapidly 

 into mercury, ammonia, and hydrogen, while the gases 

 becoming entangled in the mass impart to it that remark- 

 able turgescence which is not, however, a property of the 

 original compound (or ammonium amalgam), but merely 

 an accidental result of its decomposition. 



As to the cause of the retention of the gases, I am not 

 prepared to offer an opinion, further than that its explana- 

 tion would probably involve physical rather than chemical 

 considerations. 



I have to express my obligation to the kindness of 



n 2 



