BROMINE.
Bromine is an elementary substance, which was first recognized as such
in the year 1826. It was detected by Antoine Jerome Balard, a French
chemist, who, at the age of twenty-four, was so fortunate and skillful
as to discover this interesting substance. He lived at Montpellier,
not far from Marseilles and but a few miles from the Mediterranean.
The waters of this great inland sea contain about one-tenth more
mineral salts than those of the larger oceans, and so it has long
been the custom along the southern coasts of France to evaporate
these waters for the production of common salt. After this principal
constituent is removed, there remains a strong brine called bittern.
While experimenting upon this bittern, Balard was struck by a peculiar
orange-red coloration of great intensity which appeared at certain
stages of his work. Upon further study, he was able to demonstrate that
this color was due to an elementary substance hitherto unrecognized.
Thus he had the felicity of securing for his name permanent renown as
one of the few philosophers who have been able to detect a new member
of that family of prime and fundamental materials from which is built
the structure of the universe.
It has already been stated that the elements at present acknowledged
are less than seventy in number, and some of these were known to
the ancients. In some cases, a single individual has been able to
recognize several new ones: thus Scheele has already been mentioned
as the discoverer of manganese, barium, and chlorine. So it appears
that of all the eminent men, whose conscientious labors contribute to
the building of the science of chemistry as a noble and harmonious
edifice, necessarily but few can possibly hope to attain the specially
conspicuous honor of having their names forever associated with the
first discovery of any of the primary elements. An interesting story is
told of the eminent German chemist, Justus von Liebig, in connection
with this particular subject. Some years before Balard’s discovery
there was sent to Liebig, from a German establishment where salt brines
were employed, a flask—whose contents were afterwards found to contain
bromine, or at least to be very rich in bromine—with the request that
he examine the contents. The general appearance of the substance
seemed to be that of chloride of iodine, and this circumstance led
Liebig to neglect making a more searching investigation. After Balard
had published his discovery, Liebig perceived his own unfortunate
oversight, and occasionally, of course not without some bitter regret,
he displayed to his friends this interesting flask, to show them how
one might fail to make a discovery of the first importance by reason of
some trifling oversight.[4]
[4] SCHUTZENBERGER, PAUL: _Traité de Chimie Générale_. Paris, 1880. i,
375.
Distribution of Bromine.
The name bromine is derived from a Greek word (βρῶμσς, _bromos_, a bad
smell) which suggests the very pungent odor of its vapor. The substance
occurs in the brine of the ocean and in that of mineral springs. But of
course it does not exist there in the uncombined form; instead it is
united with certain metals in the form of bromides. In sea-water the
principal bromide is bromide of magnesium (MgBr₂).
Experimental Preparation of Bromine.
Bromine may be prepared by anyone who is willing to take a little
trouble.
Place in any suitable glass vessel a small amount of manganese dioxide,
some potassic bromide (commonly known as bromide of potassium), then
some water, and finally a small quantity of chlorohydric acid. Bromine
is almost instantly liberated, and shows its presence by imparting
to the liquid an orange hue. If the vessel is covered lightly, and
then gentle heat is applied to it, the bromine will be expelled
from the liquid and will appear above it as a heavy vapor of a rich
reddish-brown color. Some care must be exercised however in conducting
this experiment, since the vapor is very irritating to the eyes and
also to the throat, and it has a general corrosive effect upon most
substances with which it comes in contact.
Chemical Properties of Bromine.
In its chemical relations bromine shows very decided resemblances to
chlorine, having affinities for the same substances, only less in
intensity. Since its discovery it has found a considerable number
of uses. Thus it is an important substance in the processes of
photography; and the enormous expansion and growth of this art within
a very few years has required in the aggregate large quantities of
bromine. The considerable demand for bromine, which at first increased
its price, has produced, as might have been anticipated, a stimulating
influence upon the manufacture of it. This has led to greatly increased
production of the substance, not only in Europe but also in the
United States. In Pennsylvania, Ohio, and West Virginia it has become
an important article of manufacture; in fact, the United States now
furnishes the largest proportion of the entire amount of the material
produced in the world.
One of the most important compounds of bromine is that produced by
its union with silver. We refer to argentic bromide (commonly called
bromide of silver, AgBr). This substance may be easily produced by the
following simple experiment.
[Illustration: FIG. 24.—Louis Jacques Mandé Daguerre, from whom the
daguerreotype was named: born at Cormeilles, (France,) 1789; died,
1851.]
To a solution of potassic bromide in water add a water solution of
argentic nitrate; a white, or yellowish-white precipitate immediately
appears.
The chemical change is represented by the following equation:
=KBr= + =AgNO₃=
One molecule of One molecule of
Potassic bromide, Argentic nitrate,
119 169½
parts by weight. parts by weight.
\____________________________________/
|
288½
= =AgBr= + =KNO₃=
One molecule of One molecule of
Argentic bromide, Potassic nitrate,
187½ 101
parts by weight. parts by weight.
\____________________________________/
|
288½
This argentic bromide produced, at first nearly white in color, has
the power of becoming black upon exposure to light, and it is this
important property which makes the substance suitable for use in the
processes of photography.
Again in the form of potassic bromide, bromine has had a very wide and
beneficent use as a remedial agent; it is still largely used in the
manufacture of the salt mentioned.
READING REFERENCE.
Liebig, His Life-Work in Chemistry. =Hofman=, A. W.—Jour. of Chem. Soc.
of London. xxviii, 1065.
[Illustration: FIG. 25.—Photographer at work in a room lighted through
a window of red glass. (Red glass cuts off the chief actinic, or
chemical, rays of sunlight.)]