Chapter XI: 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.

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.