The use of bromine in the extraction of gold (q.v.) was proposed by R. Wagner (Dingler’s Journal, 218, p. 253) and others, but its cost has restricted its general application. Bromine is used extensively in organic chemistry as a substituting and oxidizing agent and also for the preparation of addition compounds. Reactions in which it is used in the liquid form, in vapour, in solution, and in the presence of the so-called “bromine carriers,” have been studied. Sunlight affects the action of bromine vapour on organic compounds in various ways, sometimes retarding or accelerating the reaction, while in some cases the products are different (J. Schramm, Monatshefte fur Chemie, 1887, 8, p. 101). Some reactions, which are only possible by the aid of nascent bromine, are carried out by using solutions of sodium bromide and bromate, with the amount of sulphuric acid calculated according to the equation 5NaBr + NaBrO3 + 6H2SO4 = 6NaHSO4 + 3H2O + 6Br. (German Patent, 26642.) The diluents in which bromine is employed are usually ether, chloroform, acetic acid, hydrochloric acid, carbon bisulphide and water, and, less commonly, alcohol, potassium bromide and hydrobromic acid; the excess of bromine being removed by heating, by sulphurous acid or by shaking with mercury. The choice of solvent is important, for the velocity of the reaction and the nature of the product may vary according to the solvent used, thus A. Baeyer and F. Blom found that on brominating orthoacetamido-acetophenone in presence of water or acetic acid, the bromine goes into the benzene nucleus, whilst in chloroform or sulphuric acid or by use of bromine vapour it goes into the side chain as well. The action of bromine is sometimes accelerated by the use of compounds which behave catalytically, the more important of these substances being iodine, iron, ferric chloride, ferric bromide, aluminium bromide and phosphorus. For oxidizing purposes bromine is generally employed in aqueous and in alkaline solutions, one of its most important applications being by Emil Fischer (Berichte, 1889, 22, p. 362) in his researches on the sugars. The atomic weight of bromine has been determined by J. S. Stas and C. Marignac from the analysis of potassium bromide, and of silver bromide. G. P. Baxter (Zeit. anorg. Chem. 1906, 50, p. 389) determined the ratios Ag: AgBr, and AgCl: Ag Br.
Hydrobromic Acid.—This acid, HBr, the only compound of hydrogen and bromine, is in many respects similar to hydrochloric acid, but is rather less stable. It may be prepared by passing hydrogen gas and bromine vapour through a tube containing a heated platinum spiral. It cannot be prepared with any degree of purity by the action of concentrated sulphuric acid on bromides, since secondary reactions take place, leading to the liberation of free bromine and formation of sulphur dioxide. The usual method employed for the preparation of the gas consists in dropping bromine on to a mixture of amorphous phosphorus and water, when a violent reaction takes place and the gas is rapidly liberated. It can be obtained also, although in a somewhat impure condition, by the direct action of bromine on various saturated hydrocarbons (e.g. paraffin-wax), while an aqueous solution may be obtained by passing sulphuretted hydrogen through bromine water. Alexander Scott (Journal of Chem. Soc., 1900, 77, p. 648) prepares pure hydrobromic acid by covering bromine, which is contained in a large flask, with a layer of water, and passing sulphur dioxide into the water above the surface of the bromine, until the whole is of a pale yellow colour; the resulting solution is then distilled in a slow current of air and finally purified by distillation over barium bromide. At ordinary temperatures hydrobromic acid is a colourless gas which fumes strongly in moist air, and has an acid taste and reaction. It can be condensed to a liquid, which boils at −64.9° C. (under a pressure of 738.2 mm.), and, by still further cooling, gives colourless crystals which melt at −88.5° C. It is readily soluble in water, forming the aqueous acid, which when saturated at 0° C. has a specific gravity of 1.78. When boiled, the aqueous acid loses either acid or water until a solution of constant boiling point is obtained, containing 48% of the acid and boiling at 126° C. under atmospheric pressure; should the pressure, however, vary, the strength of the solution boiling at a constant temperature varies also. Hydrobromic acid is one of the “strong” acids, being ionized to a very large extent even in concentrated solution, as shown by the molecular conductivity increasing by only a small amount over a wide range of dilution.
Bromides.—Hydrobromic acid reacts with metallic oxides, hydroxides and carbonates to form bromides, which can in many cases be obtained also by the direct union of the metals with bromine. As a class, the metallic bromides are solids at ordinary temperatures, which fuse readily and volatilize on heating. The majority are soluble in water, the chief exceptions being silver bromide, mercurous bromide, palladious bromide and lead bromide; the last is, however, soluble in hot water. They are decomposed by chlorine, with liberation of bromine and formation of metallic chlorides; concentrated sulphuric acid also decomposes them, with formation of a metallic sulphate and liberation of bromine and sulphur dioxide. The non-metallic bromides are usually liquids, which are readily decomposed by water. Hydrobromic acid and its salts can be readily detected by the addition of chlorine water to their aqueous solutions, when bromine is liberated; or by warming with concentrated sulphuric acid and manganese dioxide, the same result being obtained. Silver nitrate in the presence of nitric acid gives with bromides a pale yellow precipitate of silver bromide, AgBr, which is sparingly soluble in ammonia. For their quantitative determination they are precipitated in nitric acid solution by means of silver nitrate, and the silver bromide well washed, dried and weighed.
No oxides of bromine have as yet been isolated, but three oxy-acids are known, namely hypobromous acid, HBrO, bromous acid, HBrO2, and bromic acid, HBrO3. Hypobromous acid is obtained by shaking together bromine water and precipitated mercuric oxide, followed by distillation of the dilute solution in vacuo at low temperature (about 40° C.). It is a very unstable compound, breaking up, on heating, into bromine and oxygen. The aqueous solution is light yellow in colour, and possesses strong bleaching properties. Bromous acid is formed by adding bromine to a saturated solution of silver nitrate (A. H. Richards, J. Soc Chem. Ind., 1906, 25, p. 4). Bromic acid is obtained by the addition of the calculated amount of sulphuric acid (previously diluted with water) to the barium salt; by the action of bromine on the silver salt, in the presence of water, 5AgBrO3 + 3Br2 + 3H2O = 5AgBr + 6HBrO3, or by passing chlorine through a solution of bromine in water. The acid is only known in the form of its aqueous solution; this is, however, very unstable, decomposing on being heated to 100° C. into water, oxygen and bromine. By reducing agents such, for example, as sulphuretted hydrogen and sulphur-dioxide, it is rapidly converted into hydrobromic acid. Hydrobromic acid decomposes it according to the equation HBrO3 + 5HBr = 3H2O + 3Br2. Its salts are known as bromates, and are as a general rule difficultly soluble in water, and decomposed by heat, with evolution of oxygen.
Applications.—The salts of bromine are widely used in photography, especially bromide of silver. For antiseptic purposes it has been prepared as “bromum solidificatum,” which consists of kieselguhr or similar substance impregnated with about 75% of its weight of bromine. In medicine it is largely employed in the form of bromides of potassium, sodium and ammonium, as well as in combination with alkaloids and other substances.
Medicinal Use.—Bromide of potassium is the safest and most generally applicable sedative of the nervous system. Whilst very weak, its action is perfectly balanced throughout all nervous tissue, so much so that Sir Thomas Lauder Brunton has suggested its action to be due to its replacement of sodium chloride (common salt) in the fluids of the nervous system. Hence bromide of potassium—or bromide of sodium, which is possibly somewhat safer still though not quite so certain in its action—is used as a hypnotic, as the standard anaphrodisiac, as a sedative in mania and all forms of morbid mental excitement, and in hyperaesthesia of all kinds. Its most striking success is in epilepsy, for which it is the specific remedy. It may be given in doses of from ten to fifty grains or more, and may be continued without ill effect for long periods in grave cases of epilepsy (grand mal). Of the three bromides in common use the potassium salt is the most rapid and certain in its action, but may depress the heart in morbid states of that organ; in such cases the sodium salt—of which the base is inert—may be employed. In whooping-cough, when a sedative is required but a stimulant is also indicated, ammonium bromide is often invaluable. The conditions in which bromides are most frequently used are insomnia, epilepsy, whooping-cough, delirium tremens, asthma, migraine, laryngismus stridulus, the symptoms often attendant upon the climacteric in women, hysteria, neuralgia, certain nervous disorders of the heart, strychnine poisoning, nymphomania and spermatorrhoea. Hydrobromic acid is often used to relieve or prevent the headache and singing in the ears that may follow the administration of quinine and of salicylic acid or salicylates.
BROMLEY, SIR THOMAS (1530–1587), English lord chancellor, was born in Staffordshire in 1530. He was educated at Oxford University and called to the bar at the Middle Temple. Through family influence as well as the patronage of Sir Nicholas Bacon, the lord keeper, he quickly made progress in his profession. In 1566 he was appointed recorder of London, and in 1569 he became solicitor-general. He sat in parliament successively for Bridgnorth, Wigan and Guildford. On the death of Sir Nicholas Bacon in 1579 he was appointed lord chancellor. As an equity judge he showed great and profound knowledge, and his judgment in Shelley’s case (q.v.) is a landmark in the history of English real property law. He presided over the commission which tried Mary, queen of Scots, in 1586, but the strain of the trial, coupled with the responsibility which her execution involved upon him, proved too much for his strength, and he died on the 12th of April 1587. He was buried in Westminster Abbey.
See Foss, Lives of the Judges; Campbell, Lives of the Lord Chancellors.
BROMLEY, a municipal borough in the Sevenoaks parliamentary division of Kent, England, 1012 m. S.E. by S. of London by the South Eastern & Chatham railway. Pop. (1901) 27,354. It lies on high ground north of the small river Ravensbourne, in a well-wooded district, and has become a favourite residential locality for those whose business lies in London. The former palace of the bishops of Rochester was erected in 1777 in room
