1. DISTILLATION
A. R. Gomathi, M.pharm
Assistant professor
Department of pharmaceutics
Jkkm institute of health sciences College of pharmacy

10. A A A
A
B B B
B

18. PROCEDURE:
 The liquid to be distilled is filled into the flask to one-half to two-
third of its volume
 Bumping is avoided by adding small pieces of porcelain before
distillation
 A thermometer inserted into the cork and fixed to the flask below the
level of the side arm.
 Water is circulated through the condenser.
 The contents are heated gradually. The liquids begin to boil after
sometime.
 The vapour begin to rise up and passes down the side arm into the
condenser.
 The temp rises gradually and reaches constant value.
 The temperature of the distillate is noted down, which is equal to the
boiling point of the liquid.
 The vapour is condensed and collected into the receiver.
 Distillation is continued until a small volume of liquid remaining in
the flask.

22. Working:
The feed is pumped through a heater at a certain
pressure.
The liquid get heated, which enters the vapour-
liquid separator through a pressure reducing valve.
Due to drop in pressure, the hot liquid flashes,
which further enhancing the vaporization
process.
The sudden vapourization induce cooling.
The individual vapour phase molecules of high
boiling fraction get condensed, while low boiling
fraction remains as vapour.
The mixure is allowed for sufficient time, so that
liquid and vapour portions separate and attain
equilibrium.
The vapour is separated through a pipe from above
and liquid is collected from the bottom of the
separator.

26. Working:
 The mixture to be distilled is fed to the
boiler and heated.
 Fractionating column is inserted between
still and the condenser.
 Consider a mixture of two miscible liquids
A and B containing 20% of A and 80% of
B.
 Liquid A is more volatile component
having a lower boiling point .
 Liquid B is less volatile component having
a higher boiling point.
 When the boiling point of the mixture
reached, the vapour composition curves
are drawn.

27. These curves indicate that the vapour contains 60%
of A.
When this vapour is condensed, the resulting liquid
is again heated to boiling, this vapour gives the
composition containing 90% of A (second pair of
curve from the bottom).
This vapour impinging on a cool surface and get
condensed.
This fraction is revapourised by heating to its
boiling point. This boiling point curve of this
distillate indicates 98% of A. (third pair of curve
from the bottom)
This fraction of vapour impinges on a cooling
surface. This gives 4th pair of curves. Now this
vapour contains higher proportion of A.
The vapour moves to a condenser at the top of the
column and get condensed
Thus repetition of these processes yield pure A.

28. DISTILLATION UNDER REDUCED PRESSURE
It is defined as a distillation process in which the liquid is distilled at a
temperature lower than its boiling point by the application of vacuum.
Principle:
Liquid boils when vapour pressure is equal to the atmospheric pressure.
If the external pressure is reduced by applying vaccum, the boiling point of
the liquid decreases.
Therefore the liquid boils at a lower temperature.
Example:
Water bolis at 100°c at an atmospheric pressure 101.31kPa (760mmHg)
Vapour pressure of the water is 9.33kPa (70mm Hg) at 40°c.
Hence external pressure is reduced to 9.33kPa (70mm Hg) where water boils
at 40°c.
This results is an increase in the rate of mass transfer into vapour.

29. Application:
Changing physical form:
Preventing degradation of active constituent:
During extraction, concentration and processing at higher temp, the active
constituents may undergo decomposition. Hence extraction and
concentration should be done at a lower temp under reduced pressure.
Disadvantages
Not suitable for the preparation of semisolid or solid extract.
In vaccum distillation, persistant foaming occurs. This may be overcome by
adding capryl slcohol to the liquid.

30. PROCEDURE:
 The liquid to be distilled is filled into the
flask to one-half to two-third of its
volume
 Bumping is avoided by adding small
pieces of porcelain before distillation.
 The capillary tube and thermometer are
kept in place in the flask.
 The required vaccum is applied.
 The contents are heated gradually. the
temp rises and liquid gets vaporized
rapidly due to vacuum.
 The vapour passes through the condenser.
 The condensate is collected in the receiver.
 The temperature is noted down, which
would be less than the boiling point of the
liquid.

34. working:
• The flask is filled with non aqueous
liquid.
• A small amount of water is added to it.
water is filled in the steam can.
• Both the flask and the steam can be
heated simultaneously to maintain a
uniform flow od steam through the
boiling mixture.
• The mixture heats up and steam carries
the volatile oil into the condenser where
the oil gets cooled by the cold water.
• The condensed immiscible liquid is
collected in the receiver.
• It is continues till all the non aqueous
liquid distils off.
• Water and organic liquid collects in the
receiver as two distinct laters which are
separated usind a separating flask.

41. Centrifugal molecular still:
• Vaccum is applied at the center of the
vessel.
• The buket shaped vessel allowed to rotate
at high speed.
• The feed is introduced from the center of
the vessel.
• Due to the centrifugal action of the rotating
bucket, liquid moves outward over the
surface of the vessel and forms a film.
• since, the radiant heater heat the surface,
the liquid evaporates directly from the film.
• The vapour travels its mean free path and
strikes the condenser.
• The condensate is collected into another
vessel.
• The residue is collected from the bottom of
the vessel and is recirculated through the
feed port for further distillation.

42. Wiped film molecular still:
• The vessel is heated by suitable means.
• Vaccum is applied at the center of the vessel
and wipers are allowed to rotate.
• The feed is entered through the inlet of the
vessel.
• As the liquid flows down the wall, it is spread
to form s film by PTFE (poly tetra fluoro
ethylene) wipers, which are moving at arate of
3meters per second.
• The velocity of the film evaporates directly.
• The vapour travels its mean free path anf
strikes the condenser.
• The condensate is collected into a vessel.
• The residue is collected from the bottom of the
vessel and re circulated through the feed port
for further distillation.
• Capacity is about 1000litre per unit.

43. THANK YOU…………………………