GENERAL QUESTIONS IV 177From sodium hydroxide, a gas that burns with a colorless
flame (hydrogen) is evolved. From potassium nitrate a
gas that will neither burn nor support combustion (nitrogen)
is evolved.
Iron is more active than either hydrogen or nitrogen and dis-
places them
2KN0-, + 5Fe -> K 2 O-5FeO + 2N
2NaOH + Fe -» Na 2 OFe0 + 2H
The hydrogen and nitrogen are probably in the atomic state at
the moment of liberation. They change at once to ordinary
molecular N 2 and H 2 if they find nothing to combine with, but
in the presence of each other they combine to form ammonia.
- Nitrides. Place half a gram of magnesium ribbon
rolled into a ball, or half a gram of powdered magnesium, in
a small crucible. Heat it until it catches fire, put the cover
on to restrict the admission of air, and let the magnesium
burn slowly. Transfer the ash to a test tube and add a few
drops of water (cautiously). Note the odor of ammonia,
and bring a rod wet with concentrated hydrochloric acid near
the mouth of the tube, noting the white smoke.
When enough oxygen cannot come into contact with burning
magnesium to form the oxide, magnesium combines readily with
nitrogen. Of course, prolonged heating in air will convert all
nitride into oxide, but if the ash is cooled at once it contains
a considerable amount of nitride. Magnesium nitride hydrolyzes
very easily according to the reaction
Mg 3 N 2 + 6H 2 O -» 3Mg(OH) 2 + 2H 3 N
The magnesium nitride may be considered as a salt of the base
Mg(OH) 2 and the acid H 3 N. But since H 3 N is so weak an acid
that it is not usually considered as an acid at all, the hydrolysis of
its salt is correspondingly very complete.GENEEAL QUESTIONS IV- What are the distinctive physical and the distinctive chemi-
cal properties of the non-metallic elements? - Why are the non-metallic elements considered to be the
negative constituents of binary compounds?