Five points 

 deduced from 

 the mean re- 

 sults of expe- 

 Vol of Mercury! ^^X. riments 15 to 



24 having 

 been laid 



Volumes. down in rela- 



tion to rectangular axes, the curve (1) which passed through 

 them is represented in the diagram, which shows also the 

 curve (2) through five points representing the calculated 

 volumes, and a line (3) representing volumes corresponding 

 to the pressures which were applied to the top of the 

 columns of amalgam. 



The diagram and figures sufiiciently show that the com- 

 pressibility of the amalgam agrees nearly with the supposi- 

 tion of its being a mixture of gas and mercury, but that it 

 is, however, somewhat less compressible. This no doubt is 

 owing chiefly if not entirely to its want of fluidity. 



I think that from these experiments I am warranted in 

 drawing the two following conclusions, viz. : — 



1. 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 en- 

 larged volume or swelling up is due mainly, if not entirely, 

 to free gases entangled in it. 



In connection with the first of these conclusions arises 

 the further question whether the NH4 is combined with the 

 mercury. That it is so combined appears in the highest 

 degree probable from the apparently uniform difi'usion of 

 the NH4 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. 

 Seeley says, that if the radical NH4 be contained in the 

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



