10 



figures furnished by niy fifth experiment show, that if this 

 supposed NH4 gas had the normal molecukr vohime, 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 NH4 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 impait to it that remarkable turgescence, which 

 is not however a property of the original cojnpound (or 

 ammonium amalgam), 1 nit 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 Dr. 

 Roscoe for the use of the appliances of the laboratory at 

 Owens College, where the experiments were carried out, 

 and I am also indebted to him for valuable suggestions. 



