GENERAL QUESTIONS V 205
The rate of diffusion of gases, according to Graham's law, is
inversely proportioned to the square root of the densities. Thus
the ammonia in the mixture will diffuse —7=^- or 1.5 times as fast
V17
V17
as the hydrogen chloride, and at each end the gas which diffuses
through the plugs contains at first an excess of ammonia. The
residual gas in the middle is left with an excess of HC1, and when
this gas is finally expelled by heat the moist litmus at each end
turns red.
8. Hydrolysis of Ammonium Salts. Boil for some time
a solution of ammonium sulphate to which has been added
a few drops of blue litmus solution. Pass the vapors into a
flask of water containing a few drops of red litmus. The
litmus in the boiling flask slowly turns red. The litmus in
the flask in which the vapors are condensed turns blue.
The neutral salt of a base as strong as ammonium hydroxide is
practically not hydrolyzed at all in cold water, certainly not enough
to show by the litmus test. Water at 100° is ionized about ten
times as much as at ordinary temperature and consequently the
hydrolysis of the ammonium sulphate is increased:
2NH 4 + SO 4 ""
2H+
w
2NH4OH ?± 2NH3 + 2H2O
Even at 100° the hydrolysis is practically negligible except that
one hydrolysis product, NH 4 0H, is volatile, whereas the other,
H2SO4, is non-volatile. Thus, since a minute amount of ammonia
passes over with the steam, before long the accumulation of
NH4OH in the condensing flask turns litmus blue, and the residue
of H2SO4 in the boiling flask likewise shows its presence there.
GENERAL QUESTIONS V
ALKALI AND ALKALINE EARTH METALS
1. Make a table of the elements of Group I, Family A, includ-
ing lithium and sodium, giving in succeeding columns: (1) the
symbol of the element; (2) its valence in its compounds; (3) the
formula of the oxide; (4) the formula of the hydroxide; (5) the
