Skip to main content

Renin Angiotensin Mechanism.

Steam Distillation.

 

Principle:

  • A mixture of immiscible liquid boils when atmospheric pressure equals to their sum of vapour pressures.

Construction:

  • Laboratory Scale Steam Distillation Unit:

  • The general assembly of laboratory scale vacuum distillation units is as shown in the above Fig.. 

  • It consists of a metallic can to generate steam. 

  • This metallic can is fitted with a cork having two holes. 

  • A safety tube is passed through one of the holes and a bent tube is passed through the other. 

  • The safety tube should reach almost the bottom of the flask. 

  • In case the pressure inside the steam generator becomes too much, water will be forced out of the safety tube and the pressure will be released. 

  • When steam starts coming out from the safety tube; it indicates that the steam can is almost empty. 

  • The other end of the bent tube is connected to the flask containing non-aqueous liquid (for example, turpentine) through a rubber bung. 

  • This tube should reach almost the bottom of the flask. 

  • The flask is connected to a condenser through a delivery tube as shown in the Fig.. 

  • The condenser is connected to a receiver flask using an adaptor. 

  • The steam can and flask are heated by a suitable method.

Working:

  • The non-aqueous liquid or oil to be purified or extracted is placed in the flask. 

  • A small quantity of water is added to it. 

  • Fill the steam can with water. 

  • The steam can and the flask are heated simultaneously. 

  • The steam generated in the steam can pass to the flask through the bent tube. 

  • A uniform flow of steam passes through the boiling mixture in the flask. 

  • The mixture gets heated.

  • The steam carries the volatile oil and passes into the condenser. 

  • Cool water passes through the condenser. 

  • The condensed liquid is collected into the receiver as distillate. 

  • The distillate is the mixture of immiscible liquids. 

  • The immiscible liquids form separate layers which can be easily separated using a separating flask.

Uses:

  1. Steam distillation is used to separate immiscible liquids. For example, toluene water. 

  2. Most of the volatile oils are extracted by this method. For example, extraction of clove, anise and eucalyptus oil.

  3. It is used to purify liquid with high boiling point. For example, the essential oil of almonds.

  4. It is used to prepare aromatic waters.

  5. Camphor is distilled by this method.

Advantages:

  1. Useful for thermolabile substances.

Disadvantages:

  1. Not suitable when the liquids in the mixture are reactive.

Commonly Asked Questions.

  1. Define distillation and write in detail about Steam Distillation. 

  2. With help of a well labelled diagram describe the principle and working of the apparatus used for Steam Distillation.
Labels:

Popular posts from this blog

Rate of Drying Curve.

  Definition Drying is defined as the removal of liquid from a product usually with application of heat. Rate of Drying Curve. Drying process can be divided into three periods Initial Adjustment Period. Constant drying rate period. First falling drying rate period. Second falling rate period. Initial Adjustment Period (A-B): Also called the “ Heating up” period . In this period the substance gets heat and increases in temperature. Drying has not yet started. Constant drying rate period (B-C): During this period the temperature of the solid and the rate of drying remain constant. The moisture evaporating from the surface is replaced by water diffusing from the interior of the solid at a rate equal t o the rate of evaporation.  The moisture content at the end of constant rate (point C) is referred to as the critical moisture content (CMC).  At CMC, dry spots start appearing and drying rate starts falling . First falling drying rate period (C-D): This period is also called the period of
Read more

Heat Exchangers and Heat Interchangers.

  In pharmaceutical industries many types of equipments are used for transfer of heat, they can be classified as follows, Heat Exchangers. Heat Interchangers. Heat Exchangers: These devices are used for transferring heat from a fluid (Hot Gas or Steam) to another fluid (Liquid) through a metal wall. Heat Interchangers: These devices are used for transferring heat from a One liquid to another liquid or one gas to another gas through a metal wall. HEAT EXCHANGERS; The equipment used for heat transferring are known as heat exchangers. Some of the processes that involves heat transfer in pharmaceutical industries are: Preparation of starch paste (in steam jacketed kettle). Crystallization. Evaporation. Distillation.  Classification of heat exchangers On the basis of transfer of heat, heat exchangers are classified as: Direct transfer type:  The hot and cold fluids are separated by a metal wall through which the heat is transferred from hot fluid to cold fluid. E.g. shell and tube heater, 
Read more

Flash Distillation.

  Principle: When a hot mixture is allowed to enter from a high-pressure zone into a low pressure zone, the entire liquid mixture is suddenly vaporized. This process is known as flash vaporization .  During this process, the chamber is cooled.  The less volatile fraction is condensed and the more volatile component remains in the vapor phase .  This process requires time, hence liquid and vapor are kept in intimate contact until equilibrium is achieved. Flash distillation is also called equilibrium distillation because separation of two liquids takes place when liquid and vapor phases are at equilibrium. Equipment used for Flash Distillation: Construction: It consists of a pump, which is connected to a feed reservoir.  Pumps help in pumping the feed into the heating chamber.  The heating chamber is heat supplied by steam.  The other end of the pipe is directly introduced into the vapor-liquid separator through a reducing valve.  The vapor outlet is provided at the top of the separato
Read more