This document discusses distillation under reduced pressure and steam distillation. It describes the principles, construction of apparatus, procedures, advantages and disadvantages. Distillation under reduced pressure involves boiling a liquid at a lower temperature by reducing external pressure. Steam distillation allows separation of immiscible liquids or purification of high boiling substances by using steam. The key components and working of laboratory and large scale equipment are explained.

1. DISTILLATION UNDER
REDUCED PRESSURE

2. CONTENTS
• Principle
• Construction
• Working
• Advantage
• Disadvantage
• Use

3. ASSEMBLING OF APPARATUS

4. PRINCIPLE
• Liquid boils when its vapor pressure is equal
to atmospheric pressure, i.e. pressure on its
surface
• If the external pressure is reduced by applying
vacuum, the boiling point of the liquid
decreases . i.e. liquid boils at a low
temperature

5. PRINCIPLE
E.g.
• Water boils at 100°C - atmospheric pressure
of 131.31KPa
• At 40°c the vapor pressure of water- 9.33KPa
• So the external pressure is reduced to 9.33KPa
Where water boils at 40°c
The net result is increase in the rate of mass
transfer in to vapor

6. CONSTRUCTION
• Thick walled glass apparatus with
interchangeable standard glass joints are used
• Double neck distillation flask – claisen flask
• In one of the neck of the claisen flask, a
thermometer is fitted

7. ASSEMBLING OF APPARATUS

8. ASSEMBLING OF APPARATUS
• A capillary tube placed in the second neck to
prevent bumping
• This capillary tube is dipped in the boiling
liquid, so that air bubbles is drawn out
• The claisen flask is connected to a receiver
through a condenser

9. ASSEMBLING OF APPARATUS
• Vacuum pump is attached through an adapter
to the receiver
• A small manometer should be inserted
between the pump and the receiver

10. PROCEDURE :
• The liquid to be distilled is placed in the flask
• The volume should be one half to two third of the
flask
• Porcelain pieces added to the flask to prevent
bumping
• The capillary tube and thermometer are placed in
the flask

11. PROCEDURE :
• The required vacuum is applied
• The contents are heated gradually
• The temperature rises and liquid gets heated
rapidly due to vacuum

12. PROCEDURE
• The vapor passes through the condenser
• The condensate is collected in to the receiver
• The temperature is noted down which will be
less than the boiling point of the liquid

13. LARGE SCALE APPARATUS USING
VACUUM STILLS FOR DISTILLATION
UNDER REDUCED PRESSURE

14. CONSTRUCTION
• Vacuum jacketed still – stainless steel ,copper
which can withstand high vacuum
• Observation window – to see the progress of
distillation
• Steam inlet and exhaust at the bottom

15. CONSTRUCTION
• The still is connected to a condenser
• A thermometer incorporated in to the still
• A vacuum pump

16. WORKING
• The still is filled with the liquid to be distilled
• Vacuum is created by means of a vacuum
pump
• Steam is applied
• The contents heated gradually

17. WORKING
• The temperature rises and the liquid gets
vaporized rapidly due to vacuum
• Vapor passes through the condenser and
condensate is collected in to the receiver
• Normally two receivers are fitted with suitable
arrangement of cocks so that they can be used
alternatively

18. WORKING
• The distillate is collected from one while the
other is connected to the still under vacuum
therefore distillation need not be stopped

19. THANK YOU

20. STEAM
DISTILLATION

21. STEAM DISTILLATION
• Distillation is carried out with the aid of steam
• It used to separate high boiling substances
from non volatile impurities
• Used for the separation of immiscible liquids

22. STEAM DISTILLATION
• High boiling liquids can not be purified by
simple distillation because at high
temperature the liquid undergo
decomposition.
• In such cases steam distillation is used

23. PRINCIPLE
• A mixture of immiscible liquids begins to boil
when the sum of their vapor pressure is equal
to the atmospheric pressure

24. PRINCIPLE
E.g.
• Water and turpentine mixture - boils below the
boiling point of pure water ( 95.6° c)
• Turpentine 160° c water 100°c
• At this temperature (95.6° c)
VP of water = 86.245 kpa
Turpentine = 15.06 kpa
The sum of the VP = 101.31 kpa
• Which is normally atmospheric pressure

25. PRINCIPLE
• The high boiling substances may be distilled at
a temperature much below its boiling point
when water is used

26. APPLICATIONS :
• Used for the separation of immiscible liquids
e.g. toluene and water
• Extraction of volatile oils from clove, anise
seed and eucalyptus leaves

27. APPLICATIONS :
• Used in purification of liquids with high boiling
point
Essential oil of almond
• Preparation of aromatic water

28. ADVANTAGE :-
• Volatile oils can be separated at lower
temperature in steam distillation without any
decomposition and loss of aroma
• Low volatile substances with higher molecular
weight (higher than water) can be distilled

29. DISADVANTAGE
• Steam distillation is not suitable when
immiscible liquid and water react with each
other

30. APPARATUS USED FOR LABORATORY
SCALE

31. CONSTRUCTION
• It consists of a metallic steam can fitted with a
cork having two holes
• Through one hole a long tube is placed, it almost
reaches the bottom of the steam generator
• This tube act as safety tube

32. CONSTRUCTION
• If pressure inside the steam generator
increases ,water will be forced out through
the tube and pressure will relieved
• Other hole a bent tube is placed
• Other end of the bent tube is connected to
the flask containing non aqueous liquid
through a rubber bung

33. CONSTRUCTION
• This tube should reach almost bottom of the
flask
• Through the other hole of the rubber bung a
delivery tube is placed
• Delivery tube connect the flask and the
condenser

34. CONSTRUCTION
• Condenser is connected to the receiver via an
adaptor
• Provisions are made to heat the steam can
and the flask

35. PROCEDURE
• The non aqueous liquid is placed in the flask
• A small quantity of water is added to it
• Steam can is filled with water
• The steam can and the flask are heated
simultaneously, so that a uniform flow of steam
passes through the boiling mixture

36. PROCEDURE
• The mixture gets heated
• The steam carries the volatile oil and passes
in to the condenser
• Condensed immiscible liquid collected in to
the receiver

37. PROCEDURE
• Distillation continued until all the non
aqueous has been distilled
• Water and organic liquid form two separate
layers in the receiver ,which can be easily
separated using separating flask

38. EQUIPMENT USED ON LARGE SCALE

39. CONSTRUCTION
• It consists of a jacketed still with a perforated
plate which forms a false bottom.
• Manholes are provided at the top and side for
charging and discharging
• A Florentine receiver is placed between the
condenser and the still

40. WORKING
• The material from which the volatile oil has to be
separated is placed in the still above the
perforated plate
• Steam admitted to the jacket of the still
• Water and material present in the still are
heated to boiling

41. WORKING
• Stem also injected below the material through
a steam pipe from the jacket
• The steam carries the volatile oil and gets
condensed in the condenser

42. WORKING
• The condensate is collected in to the Florentine
receiver
• Most volatile oils are lighter then water and well
separated from the distillate as an upper layer
and removed from the upper spout
• Water return to the still

43. THANK YOU