1. No category

Module:4
Lecture:21 Sodium bromide
Dr. N. K. Patel
Module: 4
Lecture: 21
SODIUM BROMIDE
INTRODUCTION
Sodium bromide (NaBr) was discovered by Carl lowig in 1826. Sodium
bromide was first registered as a pesticide in USA in 1975. Now a days the
number of pesticides products containing sodium bromide are available in
the market.
Sodium bromide is used as an anti-epileptic drug and has anti-seizure
properties. Bromide is considered the second drug of choice when it comes
to controlling seizures Phenobarbital being the first. Bromide was used to treat
gynecologic seizures in women since 1857. Bromide therapy is still considered
for dogs whose seizures are considered refractory which is not controlled by
another anti-epileptic drug.
Other important reasons for considering bromide therapy are:
Effective in controlling cluster seizures
 Bromide is not processed by the liver

It is an inorganic compound. It is a high-melting white, crystalline solid
that resembles sodium chloride. It is a widely used source of the bromide ion
and has many applications. Sodium bromide is the one of the most utilized
alkali bromide and salt of hydrobromic acid. It is available in the form of
crystals or powder. From aqueous solution sodium bromide crystallizes as a
dihydrate and monohydrate NaBr2.H2O at below 510C, while above it
crystallizes as the anhydrous compound.
NaBr crystallizes in the same cubic motif as NaCl, NaF and NaI. The
anhydrous salt crystallizes above 50.70C. It is produced by treating sodium
hydroxide with hydrogen bromide.
NPTEL
1
Module:4
Lecture:21 Sodium bromide
Dr. N. K. Patel
MANUFACTURE
1. By neutralization of sodium hydroxide
Raw materials
Basis: 1000kg sodium bromide by neutralization of sodium hydroxide
Sodium hydroxide
380kg
Hydrobromic acid
760kg
Reaction
Manufacture process
Sodium bromide can be produced by neutralization method, in which
solution of sodium hydroxide or sodium carbonate was neutralized using
hydrobromic acid which should be free from bromine. For neutralization
process, solution of sodium hydroxide was introduced into the reactor having
stirrer where it was treated with hydrobromic acid at ambient temperature.
Mother liquor
Water vapor
Steam
out
Reactor
Evaporator
Steam
in
Crystallizer
Filter
Hydrobromic
acid
NaOH
solution
Cold
air out
Hot
air
Dryer
Sodium
bromide
Figure: Manufacture of sodium bromide by neutralization
Block diagram of manufacturing process
Diagram with process equipment
NPTEL
2
Module:4
Lecture:21 Sodium bromide
Dr. N. K. Patel
Animation
As the neutralization reaction proceed amount of water in system was
increased. After neutralization steps reaction mass was transferred to
evaporating tank where water vapour was removed. Concentrated sodium
bromide solution was sent to the crystallizer tank where sodium bromide was
crystallized.
The temperature of the crystallizing system should be kept below 510C.
So, a hydrated sodium bromide crystal was obtained. While anhydrous
sodium bromide crystals were obtained above 510C temperature. Mother
liquor was separated out via filtration and recycled to the reactor. While a
crystal of sodium bromide was sent to a dryer and dried product was then
sent for packaging section.
2. By using excess of bromine
Raw materials
Basis: 1000kg sodium bromide by using excess bromine
Excess bromine
1553kg
Sodium hydroxide
380kg
Reaction
Manufacture process
Generally this process is used for preparing commercial quantity of
sodium bromide.
Excess of bromine was added into a reaction kettle containing sodium
hydroxide solution under continuous stirring at ambient temperature. Then the
excessive bromine-NaOH solution was transferred to evaporating tank where
it was evaporated to dryness.
After that it was treated with reducing agent in reducing tank.
Generally activated carbon or formic acid was used as reducing agent
which converts the sodium bromate into sodium bromide.
NPTEL
3
Module:4
Lecture:21 Sodium bromide
Activated carbon
or formic acid
Water vapor
Filter
Excess
bromine
NaOH
solution
Dr. N. K. Patel
Steam
out
Reactor
Evaporator
Steam
in
Reducing agent
for purification
Reducing
tank
Cold
air out
Hot
air
Dryer
Sodium
bromide
Figure: Manufacture of sodium bromide using excess bromine
Block diagram of manufacturing process
Diagram with process equipment
Animation
Health and safety factors
The LD50 for this compound taken orally by rats is 3.5gm/kg body
weight. The gastrointestinal and central nervous system of human can be
affected by sodium bromide. Gastrointestinal effects include nausea and
vomiting, foul breath, anorexia, weight loss, constipation and dehydration.
Due to exposure of large amounts of sodium bromide, immediate abdominal
pain may occur in a single dose. Neurological effects include the headache,
slurred speech, impaired memory and intellectual capacity and drowsiness.
PROPERTIES






NPTEL
Molecular formula
Molecular weight
Appearance
Odour
Boiling point
Flashpoint
: NaBr
:102.89gm/mole
: White powder
: Odourless
: 13960C
: 8000C
4
Module:4
Lecture:21 Sodium bromide
 Melting point
 Density
 Refractive index
 Solubility
Dr. N. K. Patel
: 7470C (anhydrous)
360C (dihydrate)
: 3.20gm/cm3 (anhydrous)
2.18gm/cm3 (dihydrate)
: 1.6459
: Soluble in water, methanol
USES
Sodium bromide is useful inorganic bromide in industry
As a hypnotic, anticonvulsant and sedative in medicine
Used in conjunction with chlorine as disinfectant for swimming pools
Used to prepare dense fluids used in oil wells
It can be used as a source of the chemical element bromine this can
be done by treating an aqueous solution of NaBr with chlorine gas
 Used widely as a hypnotic, anticonvulsant and sedative in medicine
 Its action is due to the bromide ion, and for this reason potassium
bromide is equally effective





NPTEL
5