VALENCE 157the contents of the absorption flask and the absorption tube, and,
using litmus as an indicator, add enough more 6iV HC1 to just
neutralize the ammonia in the absorption flask. Evaporate the
solution in a porcelain dish on the hot plate to obtain solid am-
monium chloride, according to Note 6 (6), page 12. Preserve the
product in a 2-ounce cork-stoppered bottle.
QUESTIONS- Burn a little calcium in the air and test the ash for nitride.
How? - Give reasons for regarding the action of magnesium nitride
with water as an example of hydrolysis. Remember that hy-
drolysis is the exact reverse of neutralization and produces an
acid and a base from a salt and water. What is the acid and what
is the base in this case? - Why is it necessary to mix the magnesium nitride with
an inert material such as sand before adding water? - The layer from the top of the crucible will often contain a
black substance as well as a white, particularly so if the gases
from the flame entered under the lid of the crucible. What is this
black substance, and why does it form? - On the basis that air contains 4 volumes of nitrogen to 1
volume of oxygen and that all the oxygen and nitrogen that enter
under the lid of the crucible combine to form solid oxide and
nitride, calculate what fraction of the magnesium would be con-
verted to nitride.
Experiments
VALENCE
The elements are divided into two classes, metals and non-
metals. Chemically the properties of the metals are as different
from those of the non-metals as physically, for the metals form the
electropositive constituents of compounds, whereas the non-metals
form the electronegative constituents.
It must be remembered that an uncombined element is elec-
trically neutral, but every element, with the exception of the rare
gases, has a more or less strong tendency to assume an electrified
condition, the strength of which tendency is indicated by the posi-
tion of the element in the electromotive series. When a metal
and a non-metal combine chemically with each other we can con-