DISTILLATION UNDER REDUCED PRESSURE.pptx
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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.
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DISTILLATION UNDER REDUCED PRESSURE.pptx
- 2. CONTENTS โข Principle โข Construction โข Working โข Advantage โข Disadvantage โข Use
- 4. PRINCIPLE โข Liquid boils when its vapor pressure is equal to atmospheric pressure, i.e. pressure on its surface โข 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. โข Water boils at 100ยฐC - atmospheric pressure of 131.31KPa โข At 40ยฐc the vapor pressure of water- 9.33KPa โข So the external pressure is reduced to 9.33KPa Where water boils at 40ยฐc The net result is increase in the rate of mass transfer in to vapor
- 6. CONSTRUCTION โข Thick walled glass apparatus with interchangeable standard glass joints are used โข Double neck distillation flask โ claisen flask โข In one of the neck of the claisen flask, a thermometer is fitted
- 8. ASSEMBLING OF APPARATUS โข A capillary tube placed in the second neck to prevent bumping โข This capillary tube is dipped in the boiling liquid, so that air bubbles is drawn out โข The claisen flask is connected to a receiver through a condenser
- 9. ASSEMBLING OF APPARATUS โข Vacuum pump is attached through an adapter to the receiver โข A small manometer should be inserted between the pump and the receiver
- 10. PROCEDURE : โข The liquid to be distilled is placed in the flask โข The volume should be one half to two third of the flask โข Porcelain pieces added to the flask to prevent bumping โข The capillary tube and thermometer are placed in the flask
- 11. PROCEDURE : โข The required vacuum is applied โข The contents are heated gradually โข The temperature rises and liquid gets heated rapidly due to vacuum
- 12. PROCEDURE โข The vapor passes through the condenser โข The condensate is collected in to the receiver โข 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 โข Vacuum jacketed still โ stainless steel ,copper which can withstand high vacuum โข Observation window โ to see the progress of distillation โข Steam inlet and exhaust at the bottom
- 15. CONSTRUCTION โข The still is connected to a condenser โข A thermometer incorporated in to the still โข A vacuum pump
- 16. WORKING โข The still is filled with the liquid to be distilled โข Vacuum is created by means of a vacuum pump โข Steam is applied โข The contents heated gradually
- 17. WORKING โข The temperature rises and the liquid gets vaporized rapidly due to vacuum โข Vapor passes through the condenser and condensate is collected in to the receiver โข Normally two receivers are fitted with suitable arrangement of cocks so that they can be used alternatively
- 18. WORKING โข 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
- 21. STEAM DISTILLATION โข Distillation is carried out with the aid of steam โข It used to separate high boiling substances from non volatile impurities โข Used for the separation of immiscible liquids
- 22. STEAM DISTILLATION โข High boiling liquids can not be purified by simple distillation because at high temperature the liquid undergo decomposition. โข In such cases steam distillation is used
- 23. PRINCIPLE โข 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. โข Water and turpentine mixture - boils below the boiling point of pure water ( 95.6ยฐ c) โข Turpentine 160ยฐ c water 100ยฐc โข At this temperature (95.6ยฐ c) VP of water = 86.245 kpa Turpentine = 15.06 kpa The sum of the VP = 101.31 kpa โข Which is normally atmospheric pressure
- 25. PRINCIPLE โข The high boiling substances may be distilled at a temperature much below its boiling point when water is used
- 26. APPLICATIONS : โข Used for the separation of immiscible liquids e.g. toluene and water โข Extraction of volatile oils from clove, anise seed and eucalyptus leaves
- 27. APPLICATIONS : โข Used in purification of liquids with high boiling point Essential oil of almond โข Preparation of aromatic water
- 28. ADVANTAGE :- โข Volatile oils can be separated at lower temperature in steam distillation without any decomposition and loss of aroma โข Low volatile substances with higher molecular weight (higher than water) can be distilled
- 29. DISADVANTAGE โข Steam distillation is not suitable when immiscible liquid and water react with each other
- 30. APPARATUS USED FOR LABORATORY SCALE
- 31. CONSTRUCTION โข It consists of a metallic steam can fitted with a cork having two holes โข Through one hole a long tube is placed, it almost reaches the bottom of the steam generator โข This tube act as safety tube
- 32. CONSTRUCTION โข If pressure inside the steam generator increases ,water will be forced out through the tube and pressure will relieved โข Other hole a bent tube is placed โข Other end of the bent tube is connected to the flask containing non aqueous liquid through a rubber bung
- 33. CONSTRUCTION โข This tube should reach almost bottom of the flask โข Through the other hole of the rubber bung a delivery tube is placed โข Delivery tube connect the flask and the condenser
- 34. CONSTRUCTION โข Condenser is connected to the receiver via an adaptor โข Provisions are made to heat the steam can and the flask
- 35. PROCEDURE โข The non aqueous liquid is placed in the flask โข A small quantity of water is added to it โข Steam can is filled with water โข The steam can and the flask are heated simultaneously, so that a uniform flow of steam passes through the boiling mixture
- 36. PROCEDURE โข The mixture gets heated โข The steam carries the volatile oil and passes in to the condenser โข Condensed immiscible liquid collected in to the receiver
- 37. PROCEDURE โข Distillation continued until all the non aqueous has been distilled โข 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 โข It consists of a jacketed still with a perforated plate which forms a false bottom. โข Manholes are provided at the top and side for charging and discharging โข A Florentine receiver is placed between the condenser and the still
- 40. WORKING โข The material from which the volatile oil has to be separated is placed in the still above the perforated plate โข Steam admitted to the jacket of the still โข Water and material present in the still are heated to boiling
- 41. WORKING โข Stem also injected below the material through a steam pipe from the jacket โข The steam carries the volatile oil and gets condensed in the condenser
- 42. WORKING โข The condensate is collected in to the Florentine receiver โข Most volatile oils are lighter then water and well separated from the distillate as an upper layer and removed from the upper spout โข Water return to the still
- 43. THANK YOU