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.

Popular posts from this blog

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 ...

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 ...

Glycogenesis.

  Definition: Biosynthesis of Glycogen from Glucose is called Glycogenesis. Glycogen is synthesized  Depending on the demand for glucose and ATP (energy), insulin promotes the glucose conversion into glycogen. Glycogen is the major storage form of carbohydrate in animals similar to starch in plants. It is a homopolymer made up of repeated units of α- D glucose and each molecule is linked to another by 1→4 glycosidic bonds . Once there is a chain consisting of 8 to 10 glycosidic residues in the glycogen fragment, branching begins by 1→6 linkages . Glycogen is stored in liver and skeletal muscles. Location: Cytoplasm of cells in the muscle, liver, and adipose tissue. Steps Involved in Glycogenesis: Glucose is converted into glucose-6-phosphate by the action of glucokinase or hexokinase  with conversion of ATP to ADP. Glucose-6-phosphate is converted into glucose-1-phosphate by the action of phosphoglucomutase. Glucose-1-phosphate is converted into UDP-glucose by the actio...