Synthetic Inorganic Chemistry

CHAPTER VI

ELEMENTS OF GROUP III OF THE

PERIODIC SYSTEM

Boron and aluminum, the first two members of this group, are

the only ones which are classed among the common elements.

On this account, and also because the difference in properties

between Family A and Family B is far less marked than in Groups I

and II, the whole group is taken up under one heading.

The characteristics of this group are that the elements possess

a valence of 3, and that the oxides, M2O3, have but a weakly

developed basic character. Boron, in fact, shows practically

no base-forming properties, but forms rather a weak acid. The

oxide of aluminum displays both basic and acidic properties;

that is, it is amphoteric. The remaining elements are more dis-

tinctly base-forming than aluminum, without, however, approach-

ing in any way the alkaline earth metals in this respect.

PREPARATION 23
BORIC ACID, H3BO3
In this preparation, borax, the sodium salt of tetraboric acid,
is chosen as the source of boron. Although boron is decidedly a
non-metal, still its acid-forming characteristics are not highly
developed and its acids are readily displaced by strong acids from
solutions of their salts. Thus tetraboric acid, H2B4O7, would be
set free from borax by hydrochloric acid, but the acid which
actually crystallizes is the more highly hydrated orthoboric acid,
H3BO3.
Materials: borax, NaaB^-lOHaO, 96 grams = 0.25 F.W.
12.ZVHC1.
methyl orange solution.
Apparatus: 600-cc. beaker.
5-inch funnel.
suction filter and trap bottle.
5-inch watch glass,
iron ring and ring stand.
Bunsen burner,
towel and rubber band.
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