arted. (See NIGERIA and BUSSA.)

BORIC ACID, or BORACIC ACID, H3BO3, an acid obtained by dissolving boron
trioxide in water. It was first prepared by Wilhelm Homberg (1652-1715)
from borax, by the action of mineral acids, and was given the name _sal
sedativum Hombergi_. The presence of boric acid or its salts has been
noted in sea-water, whilst it is also said to exist in plants and
especially in almost all fruits (A.H. Allen, _Analyst_, 1904, 301). The
free acid is found native in certain volcanic districts such as Tuscany,
the Lipari Islands and Nevada, issuing mixed with steam from fissures
in the ground; it is also found as a constituent of many minerals
(borax, boracite, boronatrocalcite and colemanite).

The chief source of boric acid for commercial purposes is the Maremma of
Tuscany, an extensive and desolate tract of country over which jets of
vapour and heated gases (_soffioni_) and springs of boiling water spurt
out from chasms and fissures. In some places the fissures open directly
into the air, but in other parts of the district they are covered by
small muddy lakes (_lagoni_). The soffioni contain a small quantity of
boric acid (usually less than 0.1%), together with a certain amount of
ammoniacal vapours. In order to obtain the acid, a series of basins is
constructed over the vents, and so arranged as to permit of the passage
of water through them by gravitation. Water is led into the highest
basin and by the action of the heated gases is soon brought into a state
of ebullition; after remaining in this basin for about a day, it is run
off into the second one and is treated there in a similar manner. The
operation is carried on through the entire series, until the liquor in
the last basin contains about 2% of boric acid. It is then run into
settling tanks, from which it next passes into the evaporating pans,
which are shallow lead-lined pans heated by the gases of the soffioni.
These pans are worked on a continuous system, the liquor in the first
being concentrated and run off into a second, and so on, until it is
sufficiently concentrated to crystallize. The crystals are purified by
recrystallization from water. Artificial soffioni are sometimes prepared
by boring through the rock until the fissures are reached, and the water
so obtained is occasionally sufficiently impregnated with boric acid to
be evaporated directly. Boric acid is also obtained from
boronatrocalcite by treatment with sulphuric aci