The presence of ammonic chloride in such cases must be avoided.
~Detection.~--Compounds of ammonium are detected by their evolving
ammonia when mixed or heated with any of the stronger bases. The ammonia
is recognised by its odour, by its alkaline reaction with litmus paper,
and by yielding white fumes, when brought in contact with fuming acid.
In consequence of the use of ammonium salts and ammonia as reagents, it
is necessary to make a special test for and determination of
ammonium.[94] In the ordinary course of work it will be "lost on
ignition." The determination presents little difficulty, and is based on
the method used for its detection.
[Illustration: FIG. 61.]
~Solution and Separation.~--Although ammonium salts are soluble in
water, there is no necessity for dissolving them. The compound
containing the ammonia is boiled with an alkaline solution; and the
liberated ammonia condensed and collected. The substance is weighed out
into a flask of about 200 c.c. capacity. The flask is closed with a
rubber cork perforated to carry a 20 c.c. pipette and a bulb exit tube.
The latter is connected with a receiver, which is a small flask
containing dilute hydrochloric acid (fig. 61). The flask containing the
substance is corked, and the greater part of the soda solution is run in
from the pipette.
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