What is sodium bromide?

The  sodium bromide is a chemical species belonging to the salts of inorganic origin. Its structure is composed of the halogen bromine and the metallic element sodium in a 1: 1 ratio. Its chemical formula is NaBr and it is in a solid state of aggregation under standard temperature and pressure conditions (25 ° C and 1 atm).

Normally it can be seen as a white powder, and it is considered a crystalline type compound that also exhibits hygroscopic behavior; that is, it has the ability to absorb moisture from its surroundings.

Similarly, sodium bromide has physical characteristics very similar to another ionic compound of the same metal: sodium chloride. This chloride is represented as NaCl, which is more commonly known as common salt or table salt.

It has a large number of uses in different fields of science; for example, it is used in the production of various types of drugs (sedatives, hypnotics, anticonvulsants, among others), as well as in organic syntheses and even in photography applications.

Chemical structure

Sodium bromide occurs in the solid phase and, like many other inorganic salts, has a crystalline structural conformation.

This crystalline molecule, made up of a bromine and a hydrogen atom, has a face-centered cubic-type conformation, such as the halide-type salts of the same metal (NaI, NaF and NaCl).

This molecular arrangement forms the structural basis of many compounds, in which the ordering is carried out so that each ion remains in the center of an octahedral figure, as shown in the following image.

In this type of crystal it can be observed how each of the ions has around it six other ions —which have an opposite electric charge— which are located at the ends of the octahedral figure.

Likewise, the structure of this ionic substance implies that it has a high melting point of approximately 747 ° C, being found commercially in its two forms: an anhydrous species (without water molecules) and a dihydrated species (with two water molecules in its structural formula (NaBr · 2H 2 O)), whose melting points are different.

Sodium bromide originates from the chemical reaction that occurs between hydrogen bromide (BrH, a hydrogen halide in the gas phase) and sodium hydroxide (NaOH, a strong base in the solid phase and with hygroscopic properties).

In this way it is manufactured commercially, by adding an excess of bromine to a NaOH solution. Thus a bromide / bromine mixture is formed. Subsequently, the resulting products are subjected to evaporation until dry, and are treated with carbon to generate the reaction of reduction of the bromate ion (BrO  ) to the bromide ion (Br  ).


Similarly, this inorganic salt can also be produced through a neutralization reaction of sodium carbonate (Na 2 CO 3 ) with bromic acid (HBrO 3 ), following the same procedure described above.

Through a synthesis, it is possible to produce this substance through the reaction between iron with bromine and water. As a product of this reaction, the ferrous-ferric bromide species originates.

Subsequently, this formed species (represented as FeBr 2 / FeBr 3 ) is dissolved in water and a certain amount of sodium carbonate is added. Finally, the solution is filtered and goes through an evaporation process in order to finally obtain the sodium bromide.

Properties of sodium bromide

– It is commonly found in a solid state of aggregation, in the form of a white powder.

– It has a crystalline structure, with a cube-shaped molecular arrangement centered on the faces.

– The melting point of this substance is approximately 747 ° C for its anhydrous form and 36 ° C for its dihydrated form, presenting decomposition before melting.

– It is made up of a sodium ion (Na + ) and a bromide ion (Br  ), with a molar mass or molecular weight of 102.89 g / mol.

– Its boiling point is quite high, observed at 1390 ° C (equivalent to 2530 ° F or 1660 K).

– The solubility of this species is around 94.32 g / 100 ml in water at 25 ° C, increasing with increasing temperature.

– When subjected to heating to the point where it decomposes, this substance releases bromine and sodium oxide gases which are considered toxic.

– The density of the anhydrous form of sodium bromide is 3.21 g / cm 3 , while that of the dihydrate compound is 2.18 g / cm 3 .

– Its solubility in alcohol is considered moderate, as in other solvents such as pyridine, ammonia and hydrazine.

– Presents insolubility against acetonitrile and acetone.

Uses / applications

– In the medical area it is used as a drug for a large number of conditions that cause seizures and as a therapy to prevent epilepsy in patients with Wolf-Hirschhorn syndrome, as well as in sedative and hypnotic treatments.

– In veterinary medicine it is used in dogs that have seizure disorders due to the side effects of drugs such as primidone or phenobarbital.

– In the field of the oil industry it is used in the preparation processes of certain fluids of varying density that are used in oil wells .

– In the area of ​​biological research, its microbiocidal properties have been proven; that is, it is used to control the development of different types of bacteria.

– In certain organic-type syntheses, this inorganic salt is used for the preparation of other species consisting of bromine. For example, by means of the Finkelstein reaction certain higher reactivity alkyl halides are obtained, one of which used to be widely used in photography.

– In the cleaning and disinfection area, sodium bromide is used in combination with chlorine for the sanitation of large volumes of water, such as in swimming pools and hot tubs.

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