Hazard
Toxic by inhalation and ingestion.
Physical properties
White crystalline powder or granules; saline and slight bitter taste; cubic structure; density 3.20 g/cm3; melts at 747° C; vaporizes at 1,390°C; vapor pressure 1 torr at 806°C and 5 torr at 903°; highly soluble in methanol, 16.7 g/100mL.
The dihydrate is a white crystalline solid; density 2.18 g/cm3; decomposes at 36°C; soluble in water; sparingly soluble in methanol.
Occurrence
Sodium bromide occurs in seawater at an average concentration of 0.008%. It also is found naturally in some salt deposits. It is used in photography for preparing light-sensitive silver bromide emulsions. The salt also is used as a bleaching and disinfecting agent for water treatement in swimming pools, health spas, and hot tubs. Other uses are as a catalyst for partial oxidation of hydrocarbons, for increasing density of aqueous drillng fluids for oil wells, as an electrolyte component in sodium-halogen batteries, as a brominating agent in organic synthesis, in preparing bromide salts, and as a laboratory reagent. Sodium bromide is used in medicine as a sedative and hypnotic.
Definition
ChEBI: An inorganic sodium salt having bromide as the counterion.
Definition
sodium bromide: A white crystallinesolid, NaBr, known chiefly asthe dihydrate (monoclinic; r.d. 2.17),and as the anhydrous salt (cubic; r.d.3.20; m.p. 747°C; b.p. 1390°C). The dihydrateloses water at about 52°Cand is very slightly soluble in alcohol.Sodium bromide is prepared by thereaction of bromine on hot sodiumhydroxide solution or of hydrogenbromide on sodium carbonate solution.It is used in photographic processingand in analytical chemistry.
Preparation
Sodium bromide can be prepared by several methods. Pure salt can be made by neutralizing sodium hydroxide or sodium carbonate with hydrobromic acid. The solution is evaporated for crystallization:NaOH + HBr → NaBr + H2O NaCO3 + HBr → NaBr + CO2 + H2O
Sodium bromide can be made by passing bromine through an aqueous solution of sodium hydroxide or carbonate in the presence of a reducing agent, such as ammonia, hydrazine, activated charcoal, or Fe2+ ion. A typical method involves adding iron to bromine water to form ferrosoferric bromide, Fe[FeBr5]. This double salt is dissolved in excess water followed by addition of sodium carbonate. The product mixture is filtered and the filtrate is evaporated to crystallize sodium bromide. The overall reaction may be written as follows: 3Fe + 4Br2 + 4Na2CO3 → 8NaBr + FeCO3 + Fe2(CO3)3
Another method involves adding excess bromine to a solution of sodium hydroxide. This forms sodium bromide and bromate. The product solution is evapoated to dryness. The bromate is reduced to bromide by heating with carbon: 3Br2 + 2NaOH + H2O → NaBr + NaBrO3 + 4HBr.
General Description
Sodium bromide is a brominating agent mainly used in organic synthetic reactions as a bromide source.
Flammability and Explosibility
Nonflammable
Biochem/physiol Actions
Sodium bromide can be used as a substitute for potassium bromide.
Purification Methods
Crystallise the bromide from water (0.86mL/g) between 50o and 0o, and dry it at 140o under vacuum (this purification may not eliminate chloride ion).
Incompatibilities
Sodium bromide is compatible with most non-metallic materials of construction such as polypropylene, polyethylene, fiberglass reinforced plastic (FRP), cellulose, cloth, coatings, rubbers, etc. Metals can also be used provided the sodium bromide is kept dry. If the sodium bromide becomes wet, steel will suffer general corrosion and stainless steels and aluminum will suffer pitting attack. The rates of attack will depend upon the amount of oxygen present but in general will not be rapid.
