Module:5
Lecture:30Chloroform
Dr. N. K. Patel
Module: 5
Lecture: 30
CHLOROFOrm
INTRODUCTION
Chloroform is an organic compound with formula CHCl 3. It is a
colourless, sweet-smelling dense liquid and it is a trihalomethane which is
considered somewhat hazardous. It is one of the four chloromethanes.
Chloroform readily volatilizes from soil and surface water, which then
produced phosgene, dichloromethane, formyl chloride, carbon monoxide,
carbon dioxide and hydrogen chloride as undergoes degradation in air.
Chloroform was discovered by three researchers independently of one
another. The French chemist EugèneSoubeiran was reported chloroform in
1831. It was prepared from acetone (2-propanone) as well as ethanol
through the action of chlorine bleach powder (calcium hypochlorite).
Chloroform was named and characterized in 1834 by Jean-Baptiste Dumas.
Several million tons are produced annually as a precursor to PTFE and
refrigerants, but its use for refrigerants is being phased out. Chloroform has a
multitude of natural sources, both abiotic and biogenic. Greater than 90% of
atmospheric chloroform is of natural origin.
The American physician Samuel Guthrie prepared gallons of the
material and described its "deliciousness of flavor." Independently, Justus von
Liebig also described the same compound. All early preparations used
variations of the haloform reaction.
MANUFACTURE
1. From acetone and bleaching powder
Raw material
Basis: 1000kg chloroform from acetone and bleaching powder (88%
yield)
Chlorine
1602kg
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Module:5
Lecture:30Chloroform
Dr. N. K. Patel
Methane (STP)
200kg
Reaction
Manufacture process
Acetone
Bleaching
powder
Cooler
Water
Chlrorform
Water
Water
Sulfuric
acid
Reactor
and Still
Lime
Still
Acidifier
Waste
Spent
acid
Waste
Figure: Manufacture of Chloroform from acetone and bleaching powder
Block diagram of manufacturing process
Diagram with process equipment
Animation
The bleaching powder containing about 34% available chlorine was
slowly added in the ratio of about 0.161kg per kg of water to the cast-iron still,
fitted with efficient agitation, cooling coils and heating coils. The suspension
of bleaching powder in water was properly agitated.
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Module:5
Lecture:30Chloroform
Dr. N. K. Patel
Acetone (0.045kg of acetone per 0.45kg of bleaching powder) was
slowly charged into the still and mixed with bleaching powder, where the
temperature was maintained below 430C with the help of cooling coils and
rate of addition. The pot temperature was increased upto 560C, after all the
acetone has been added. Then gradually increasing the temperature to
650C where all the chloroform formed was distilled out from the still. The
chloroform vapour were passed through a cooler and collected in a tank
fitted with an agitator. The crude material containing chloroform and water
mixturewas purified by agitation with concentrated sulfuric acid in a weight
ratio of about 0.9kg of crude chloroform (distillate) per 0.45kg of sulfuric acid.
After 2 - 3hr agitation, the crude chloroform was decanted from the acid and
charged to a still, where it was distilled over lime (calcium oxide).
The purified chloroform having purity of 99% and was obtained in
86 - 91% yield based on the acetone charged.
Continuos process
These processes may be run on a continuous basis and may use the
mixture of acetone and acetaldehyde as the raw material. Industrial ethyl
alcohol has been used to make chloroform and was the basis for the original
bleaching powder process.
2. From methane by chlorination
As described in Module:5, Lecture:29
Storage and handling
All person should be instructed and supervised in appropriate method
while handling chloroform to prevent the exposure. Proper supervision should
be given while disposing this chemical. It should be stored and place in
cooled in place. Dark green glass containers should be used for storage of
this chemical. Bulk storage containers should be proper galvanized. The
storage tanks should be equipped with vent dryer which is packed with
calcium chloride. It can be transported via trucks, rail cars, ships and drums.
Health and safety
Due to inhalation of chloroform liver and kidney get damaged. This is
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Module:5
Lecture:30Chloroform
Dr. N. K. Patel
the principal hazard of chloroform. If the concentration of chloroform inhaled
more it leads to unconsciousness and disturbance in equilibrium, upon
coontct with skin it irritates to skin as well as affect the mucous membrane but
still it is believed that medically significant quantity of chloroform are not
affect through skin contact.
Chloroform was first used as surgical anesthetic in the past years. But
later it was abandoned as narcotic concentration always leads to death.
Chloroform was also banned by FDA for use in various foods. Repeated
contact with skin and clothes results into inflammation. In open flame, at
elevated temperature, chloroform converts into the various product like
phosgene, hydrogen chloride and chlorine etc.
PROPERTIES
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Molecular formula
Molecular weight
Appearance
Odour
Boiling point
Melting point
Freezing point
Density
Vapour pressure
Solubility
: CHCl3
: 119.38gm/mole
: Colourless liquid
: Ethereal
: 61.20C
: -63.50C
: -63.50C
: 1.498gm/cm3 at 150C
: 100mm at 10.40C
: Miscible with alcohol, ether, benzene,
Petroleum ether, oils,carbon disulfide
and carbon tetrachloride
USES
 Chloroform is used in a manufacturing of the chlorodifluoromethane
which is precursor to tetrafluoroethylene
 As solvent in dyes, pesticides and pharmaceutical, rubber industry
 Used to bond pieces of acrylic glass
 As a solvent for rubber, fats oils, alkaloids, waxes, gutta-percha, resins
 As cleansing agent and as a fire extinguishers to lower freezing
temperature of carbon tetrachloride
 For anesthetic application
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