Pressures. 
9 
Five points 
deduced from 
the mean re- 
sults of expe- 
riments 15 to 
24 having * 1 2 
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 sufficiently 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, somewlmtr 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 
th£ 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. 
Seeley says, that if the radical NH 4 be contained in the 
amalgam at all, it must be in the state of gas. But the 
