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.

CHAPTER XXI.

SODIUM HYDRATE.

101. Preparation.