Bleaches bromide

Uses For bleaching bromide prints in sulfide toning with potassium cyanide as a print reducer for removing silver stains. Iodine stains on fingers disappear in hypo or sulfite. 

The presence of chloric(I) acid makes the properties of chlorine water different from those of gaseous chlorine, just as aqueous sulphur dioxide is very different from the gas. Chloric(I) acid is a strong oxidising agent, and in acid solution will even oxidise sulphur to sulphuric acid however, the concentration of free chloric(I) acid in chlorine water is often low and oxidation reactions are not always complete. Nevertheless when chlorine bleaches moist litmus, it is the chloric(I) acid which is formed that produces the bleaching. The reaction of chlorine gas with aqueous bromide or iodide ions which causes displacement of bromine or iodine (see below) may also involve the reaction... 

Because they are unstable, hypobromites are usually prepared just before use for such jobs as textile bleaching and desizing. In alkaline solutions at 50—80°C bromine reacts to form bromide and bromate. This reaction is reversed in acidic solutions. 

Hypobromites, the salts of hypobromous acid, do not keep well because they gradually disproportionate to bromide and bromate. Solutions are best prepared as needed from bromine and alkafl with cooling. Because disproportionation is catalyzed by cobalt, nickel, and copper (70), these impurities should be avoided. SoHd alkaline earth hypobromites, or more properly, bromide hypobromites such as calcium bromide hypobromite [67530-61 CaBr(OBr), have been known for many years, but the pure crystalline hydrates sodium hypobromite pentahydrate [13824-96-9] NaOBr 5H20, and potassium hypobromite tribydrate [13824-97-0], KOBr 3H20, were not described until 1952 (71). Hypobromites are strong bleaching agents, similar to hypochlorites. 

Bromine compounds are used in bleaches, antiknock gasoline, and in baking bread. Some medicines, called bromides, contain bromine. 

Bromine occurs in nature as bromide in many natural brine wells and salt deposits. It also is found in seawater at a concentration of 85 mg/L. The element was discovered by A. J. Balard and C. Lowig, independently in 1826. Bromine is used in bleaching fibers and as a disinfectant for water purification. Other appbcations are in organic synthesis as an oxidizing or brominat-ing agent in the manufacture of ethylene dibromide, methyl bromide and other bromo compounds for dyes and pharmaceutical uses as a fire retardant for plastics and in chemical analysis. Ethylene dibromide is used in anti-... 

Uses of the halide acids.—The hydrochloric acid formed as a by-product in tne manufacture of sodium sulphate from sodium chloride is sufficient to meet commercial requirements, and accordingly the acid is cheap. The largest amount of hydrochloric acid or hydrogen chloride is used in the manufacture of chlorine and chlorine products—hypochlorites, bleaching powder, and chlorates. It is also used in the manufacture of many of the metal chlorides—zinc, tin, etc. This acid is also used for general purposes in laboratories, in analytical and metallurgical work, in the manufacture of colours. Smaller quantities are used medicinally. Hydro-bromic acid or the bromides and hydriodic acid or the iodides are used medicinally, in photography, and in analytical chemistry. Hydriodic acid is an important... 

A. J. Balard 8 prepared an olive-green insoluble mass by the action of bromine water on copper oxide, vegetable colours are not bleached, but nitrogen is evolved from ammonia, and carbonic and other acids set free bromine. When heated, oxygen, bromine, and water are given off, and copper oxybromide remains. The solid is possibly a mixture of bromine and copper oxybromide and not copper hypobromite. A. J. Balard also prepared a soln. which probably contained silver hypobromite by the action of bromine water on silver oxide. The product easily decomposes into bromide and bromate. F. W. Schmidt suggested that the white floccuient precipitate obtained by the action of iodine on a very dil. ammoniacal soln. of silver nitrate is possibly silver hypoiodite. 

This is a high-tonnage chemical and one of the most important of the bromide salts commercially. High-purity grades are required in the formulation of silver bromide emulsions for photography. The compound, usually in combination with hypochlorites, is used as a bleach, notably for cellulosics. The production of sodium bromide simply involves the neutralization of HBr with NaOH or with sodium carbonate or bicarbonate. 

Bleach is usually dispensed two or three times per week by hand-adding a known volume, although the use of a timer-controlled pump is a preferred alternative. Bleach can also be used in combination with sodium bromide solution to produce hypobromous acid. 

Typically, a 40% solution of sodium bromide is used and is mixed together with bleach. 

This is essentially a two-step reaction, with hypochlorous acid being generated from the reaction of bleach with water and then the hypochlorous acid oxidizing the sodium bromide component. 

In practice, the required ratio can be different from theoretical, as quite often additional bleach is required to provide HOC1 as an oxidant for algal slimes and other forms of chlorine demand. Also, it is necessary to have a permanent source of oxidant available to effect the promotion of HOBr. However, not all the available bromine generated is lost by biocidal reaction or by (limited) volatility. There is, in fact, some degree of recycling of the bromide ion (Br ) back into HOBr, so monitoring of bromine plus the combined free and total chlorine is necessary to strike the correct halogen balance. 

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