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Towler, John. The Silver Sunbeam. Joseph H. Ladd, New York: 1864. Electronic edition prepared from facsimile edition of Morgan and Morgan, Inc., Hastings-on-Hudson, New York. Second printing, Feb. 1974. ISBN 871000-005-9

Chapter XI.
BROMINE.

Bromine.---Symbol, Br. Combining Proportion, 80. Specific Gravity, 2.966.

THIS peculiar substance was discovered in 1826 by Balard, of Montpellier. It was originally obtained from the uncrystallizable mother-liquor of sea-water, called bittern. It occurs in sea-water in small quantity as bromide of magnesium, or of an alkali; but in much larger quantities in several mineral springs, as, for instance, at Kreuznach, Cheltenham, etc., and is naturally found in many marine plants and animals.

Preparation of Bromine.

The solution of the bromides obtained by evaporation of sea-water, spring-water, or from the ashes of certain plants and animals, is submitted to a current of chlorine, which takes the place of the bromine in the salts. When the liquid ceases to assume a deeper color from the introduction of chlorine, (and great care must be taken not to add too much, because it combines with the bromine as soon as there is no base present for it to combine with,) it is well shaken with ether, which, taking up the bromine, ascends and swims on the surface. This film is then decanted, or otherwise separated, and mixed with a strong solution of potassa, by which both bromate and bromide of potassium are formed; the ether may now be removed by distillation, and the remaining solution is evaporated to dryness. The residual mass is then fused, whereby the bromate of potassa is converted into bromide of potassium, analogously with the iodate or chlorate under similar circumstances. By distilling the resulting bromide with sulphuric acid and peroxide of manganese, bromine passes off as vapor, and a sulphate of the base remains in the retort together with the manganese in a lower state of oxydation.

Bromine thus obtained contains water and bromide of carbon. The water is removed by a second distillation over recently fused chloride of calcium. Bromine is a brownish-red liquid, which solidifies at--7° 2/10, volatilizes very rapidly when exposed to the air, and boils at about 145°. Its smell is very disagreeable and pungent. A drop on the cuticle destroys it and produces a sore. It is soluble in 33 3/10, parts of water, and this solution is decomposed by exposure to light into hydrobromic acid.

Test: Chlorine liberates bromine from all its soluble compounds. Ether combines with it and collects it; solution of starch produces a yellowish-red color with it; it distills as a liquid.

Hydrobromic Acid.

Symbol, Br H. Combining Proportion, 81. Spec. Grav., 2.73.

This acid is very analogous in its formation and reactions to hydriodic acid. It can be prepared by mixing directly phosphorus, water, and bromine, or from a mixture of six parts of crystallized sulphite of soda, three parts of bromine, and one of water, and by distillation. It can be obtained also by transmitting a current of hydrosulphuric acid through water, holding in solution or suspension a small quantity of bromine; sulphur is deposited; the hydrogen combines with the bromine. By a gentle heat the fumes of hydrosulphuric acid are expelled; and by filtration the hydrobromic acid is obtained in solution.

Bromides.

These binary combinations can be obtained, as a general thing, by manipulating precisely as in the preparation of the iodides, with the single substitution of bromine for iodine. They contain in like manner, and for the same reason, the same impurities which may be manifested by the same tests, with the exception of bromic acid instead of iodic; the former of which is decomposed by chlorine.

Preparation of the Chlorides.

Chlorine.---Symbol, Cl. Combining Proportion, 35.5. Spec. Grav., 2.47.

This substance was discovered in 1774 by Scheele. Its affinity for other elements is very great, so that it does not exist free or uncombined. The great geological formation of rock-salt is a chloride of sodium, to which the ocean owes its saline taste. It combines with most of the metalloids as well as the metals, giving rise to some of the most important and interesting combinations in chemistry. Chlorine, iodine, bromine, and fluorine form analogous binaries with

hydrogen and the metals; but chlorine has greater affinities for bases than any of the others; it is, therefore, employed in separating iodine and bromine from their combinations.

Preparation.

Chlorine may be obtained from any of its binary combinations by double decomposition. Thus hydrochloric acid is a binary consisting of chlorine and hydrogen; now by adding to hydrochloric acid a material in which oxygen is loosely combined, hydrogen and oxygen unite to form water, chlorine is liberated, and a chloride of the base is at the same time formed. Take, for instance, four parts of hydrochloric acid, one part of the binoxide or black oxide of manganese, and the same quantity of water. Mix these ingredients in a flask or retort connecting with a jar filled with warm water and inverted over the pneumatic trough, or by a tube dipping to the bottom of a large tumbler. By applying heat, either from a lamp or sand-bath, an effervescence is produced, being the result of the decomposition just alluded to. The gas as it passes out displaces the water in one case and the air in the latter.

The mode by which it is procured from a chloride consists in first obtaining from the chloride hydrochloric acid, And then proceeding as before. But the two operations are combined in one, that is, they take place consentaneously by mixing all the materials together which are required in their separate formations as follows: take three parts of common salt, five of sulphuric acid, five of water, and four of binoxide of manganese, and apply heat as before; the same result will ensue as in the first case.

Properties.

This substance is a heavy gas of a greenish-yellow color, and exceedingly suffocating odor. Under a pressure of four atmospheres this gas is condensed into a liquid of a bright yellow color, whose specific gravity is 1.33. It is soluble in water, which takes up and dissolves about two volumes of this gas, and receives the taste, odor, and other properties of the gas. With very cold water chlorine enters more abundantly into combination, forming a crystalline hydrate. Chlorine in solution, when exposed to the light, soon decomposes the water, giving rise to hydrochloric acid. Chlorine has an exceedingly great affinity for hydrogen, and removes this latter body from many of its combinations, as, for example, from ammonia; still dry chlorine and hydrogen, when mixed and kept in the dark, do not combine; if brought into the full blaze of the sun, they combine and explode; if exposed to diffused light, they combine silently into hydrochloric acid. Its action upon metals in a state of fine division is in many cases very energetic; if a piece of bronze or gold-leaf be injected into a tumblerful of the moist gas, the combination is so energetic as to produce flame. The moist gas combines with the hydrogen of organic colors and bleaches them; these colors can not be restored, because the hydrogen can not be restored organically; hence we say in such an instance that the color has been destroyed. In like manner moist chlorine removes the hydrogen from putrid and miasmatic substances, as from fish, meat, and offensive localities. It is, therefore, denominated a disinfecting agent. Its combination with the hydrate of lime is the form in which it is used both for bleaching and disinfecting.

Chloride of Lime, Chlorinetted Lime, etc.

This substance is prepared by passing chlorine through sets of chambers or compartments of wicker-work containing layers of hydrate of lime. The lime absorbs a large quantity of the gas, and probably combines with it in the formation of a hypochlorite of lime. Chloride of lime is soluble to some extent in water, giving to it an alkaline reaction; its bleaching powers are more effectual when an acid is added, which liberates the chlorine. This substance is now used in photography in the preparation of the gold-toning bath. When added to chloride of gold, which is slightly acid, it renders it alkaline, and at the same time chlorine is liberated, which assists in producing pure whites on the paper, and in furnishing a chloride of gold which is more effectual in toning.


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