6 
about two-thirds of the shorter limb, into which was then 
introduced the amalgam after the latter had been wiped 
with filtering paper. Then into the end of the limb con- 
taining the amalgam, a caoutchouc stopper, perforated with 
a small opening, was immediately thrust so far that its 
upper surface came a little below the rim of the tube. The 
decomposition of the amalgam was then allowed to proceed 
for a few minutes, during which period any moisture ad- 
hering to the amalgam or present in the tube would become 
completely saturated with ammonia, and then the two gases 
would begin to escape through the perforation in the stopper 
in the proportions in which they are really evolved. Mercury 
was now poured into the open end of the longer limb until 
the amalgam just made its appearance at the top of the hole 
in the stopper, which was then closed by pushing in a piece 
of glass rod. The evolved gases being now retained in the 
tube pressed up the mercury in the longer ]imb, and it was 
from time to time drawn off by the outlet tube to prevent 
undue pressure on the stopper. When the decomposition 
was complete, which usually occurred in about hours 
(but in one case more than 2J hours were required) the 
mercury was brought to the same level in both limbs and 
the space occupied by the gases was marked on the tube. A 
little mercury was then let out so as to make the pressure 
on the gas somewhat less than that of the atmosphere, and 
the space above the stopper was filled with hydrochloric 
acid diluted with a little water. The glass rod was then care- 
fully withdrawn for an instant so that a few drops of the 
acid might enter the tube. The ammonia gas present was 
of course immediately absorbed, and the mercury having 
been again brought to the same level in both limbs, the 
space occupied by the residual hydrogen was marked on the 
tube. The volumes occupied by the gases were determined 
by finding the quantity of water required to fill them from 
a burette. 
The following are the results of four experiments : — * 
