AMMONIUM HYDRATE.
96. Preparation of Bases.--We have seen that many acids are made
by acting on a salt of the acid required, with a stronger acid.
This is the direct way. The following experiments will show that
bases may be prepared in a similar way by acting on salts of the
base required with other bases, which we may regard as stronger
than the ones to be obtained.
97. Preparation of NH4OH and NH3.
Experiment 57.--Powder 10 g. ammonium chloride, NH4Cl, in a mortar
and mix with 10 g. calcium hydrate, Ca(OH)2; recently slaked lime
is the best. Cover with water in a flask, and connect with Woulff
bottles, as for making HCl (Fig. 22); heat the flask for fifteen
minutes or more. The experiment may be tried on a smaller scale
with a t.t. if desired.
The reaction is: 2NH4Cl + Ca(OH)2 = CaCl2 + 2NH4OH. NH4OH is
broken up into NH3, ammonia gas, and water. NH4OH = NH3 + H2O.
These pass over into the first bottle, where the water takes up
the NH3, for which it has great affinity. One volume of water at
0° will absorb more than 1000 volumes of NH3. Thus NH4OH may be
called a solution of NH3, in H2O. Write the reaction.
Experiment 58.--Powder and mix 2 or 3 g. each of ammonium
nitrate, NH4NO3, and Ca(OH)2; put them into a t.t., and heat
slowly. Note the odor. 2NH4NO3 + Ca(OH)2 = ?
98. Tests.
Experiment 59.--(1) Generate a little of the gas in a t.t., and
note the odor. (2) Test the gas with wet red litmus paper. (3)
Put a little HCl into an e.d., and pass over it the fumes of NH3
from a d.t. Note the result, and write the equation. (4) Fill a
small t.t. with the gas by upward displacement; then, while still
inverted, put the mouth of the t.t. into water. Explain the rise
of the water. (5) How might NH4Cl be obtained from the NH4OH in
the Woulff bottles? (6) Test the liquid in each bottle with red
litmus paper. (7) Add some from the first bottle to 5 or 10 cc.
of a solution of FeSO4 or FeCl2, and look for a ppt. State the
reaction.
99. Formation.--Ammonia, hartshorn, exists in animal and
vegetable compounds, in salts, and, in small quantities, in the
atmosphere. Rain washes it from the atmosphere into the soil;
plants take it from the soil; animals extract it from plants.
Coal, bones, horns, etc., are the chief sources of it, and from
them it is obtained by distillation. It results also from
decomposing animal matter. NH3 can be produced by the direct
union of N and H, only by an electric discharge or by ozone. It
may be collected over Hg like other gases that are very soluble
in water.
100. Uses. --Ammonium hydrate, NH4OH, and ammonia, NH3, are used
in chemical operations, in making artificial ice, and to some
extent in medicine; from them also may be obtained ammonium
salts. State what you would put with NH4OH to obtain (NH4)2SO4.
To obtain NH4NO3. The use of NH4OH in the laboratory may be
illustrated by the following experiment:--
Experiment 60.--Into a t.t. put 10 cc. of a solution of ferrous
sulphate, FeSO4. Into another put 10 cc. of sodium sulphate
solution, Na2SO4. Add a little NH4OH to each. Notice a ppt. in
the one case but none in the other. If solutions of these two
compounds were mixed, the metals Fe and Na could be separated by
the addition of NH4OH, similar to the separation of Ag and Cu by
HCl. Try the experiment.