'بِسْمِ ٱللَّٰهِ ٱلرَّحْمَٰنِ ٱلرَّحِيمِ
“In the name of God, Most Gracious, Most Merciful”
Overview :
EXICCATION
Example:
- The temperature required to remove the water of crystallization is very important and various widely.
For example:
- In CuSO4.5H2O when heated at the 30C loss two molecules of water of crystallization forming CuSO4 .3H2O.
- At 100C it loses two more water molecules resulting in CuSO4.H2O .
- The last water molecule is removed at 200 C thus forming anhydrous CuSO4.
Process:
- Exiccation may be carried out by taking a weighed amount of the substance in a tarred dish
- It is then heated on a water bath , sand bath or in an oven with continuous stirring until a constant weight is obtained and there is no further losing weight.
- No further loss in weight indicates that exiccation has been completed and no further water loss can take place.
- Mostly a sand bath or air oven is used for this process
1- In one their humid parts are exhaled by heating.
2- In other water is absorbed by different substance.
-This is a process of drying by heating also named as process of boiling during this process it is important to take care of heat level at the close of the operation the first should be gradually suppressed otherwise the matter being left dry will be heated beyond the adjusted degrees and then the exiccation substance can be damaged
-This method is used for fluid only
Method
Isolation:
- Isolation or properly exhalation is affected by exposing the substance to the sun till it is sufficiently derived there is nothing particularly necessary to be observed expel to increase the surface of matter to be much exported to sun
- For in proportion the process of exiccation will be completed in greater or lesser time
- This method is useful for both solid and liquid
Torrification:
- Torification or (sometime called toasting) is a process of exposing solid substance to heat of the fire at such distance that it will not be endangered there are being burnt in order to make them of sufficient dryness to make them in powdered form
- Only for solid.
- Temperature is very important to be controlled in the process of exiccation because as we increase or decrease the temperature the molecules of water are evaporated from crystals specific temperature for specific crystal removes specific amount of water molecules
- It is important to control the environmental conditions when we are about to exiccation a crystals to remove the water of crystalline
Application:
DECANTATION:
Introduction:
- Decantation is a process by which a liquid is separated from a solid. The solid is allowed to settle and liquid is poured off carefully leaving the settled solid undisturbed.
Definition:
"Decantation is a process for the separation of mixtures, by removing a layer of liquid, generally one from which a precipitate has settled".
- Decanting is a process to separate mixtures. Decanting is just allowing a mixture of solid and liquid or two immiscible liquids to settle and separate by gravity.
- This process can be slow and tedious without the aid of a centrifuge. Once the mixture components have separated, the lighter liquid is poured off leaving the heavier liquid or solid behind.
- Decantation is a process to separate mixtures by removing a liquid layer that is free of a precipitate, or the solids deposited from a solution. The purpose may be to obtain a decant (liquid free from particulates) or to recover the precipitate.
Process:
• In laboratory conditions, small volumes of mixtures are decanted in test tubes. If time is not a concern, the test tube is kept at a 45° angle in a test tube rack.
• This allows the heavier particles to slide down the side of the test tube while allowing the lighter liquid a path to rise to the top. If the test tube were held vertically, the heavier mixture component could block the test tube and not allow the lighter liquid to pass as it rises.
Purpose/Aim:
- The purpose of decantation is to separate insoluble liquids from solids.
- The purpose may be either to produce a clean decant, or to remove undesired liquid from the precipitate (or other layers).
- DECANTER: A decanter is a vessel used to hold the decantation of a liquid which may contains sediments.
Principles:
- The principles of decantation are:
• Sedimentation
• Centrifugation
- Decantation is a "pouring off" of a liquid from a solid/liquid mixture. The mixture is allowed to settle,and the liquid is removed while preventing the solid from escaping.
When it is used?
-Decantation is used when one is separating part of a mixture from another and when the particles or sediments are too fine to be filtered from a liquid.
Procedure:
- The steps of decantation are given below:
1. Mixture in the container is allowed to stand for sometime
2. The solid particles will settle in time
3. The upper layer of the liquid gets cleaner
4. Separate the course particles of a solid from a liquid by pouring the liquid to a new container by the process of decantation
Examples:
1. Oil & Water: Oil floats on the top of the water. Decanting the mixture allows the oil to be poured off the water.
2. Dirt and water: Muddy water can be cleared up by decanting. The soil will sink to the bottom of the tube allowing the clear water to be poured off.
3. Cream & Milk: Cream is separated from milk by decantation. Cream rises to the top of the milk mixture and easily skimmed off.
4. Blood & plasma: A centrifuge is necessary for this decantation. Plasma can be removed from the blood by decantation
Disadvantages:
- It cannot be used to separate a mixture of a liquid and a light solid, such as chalk in water.
- The particles of chalk are suspended I the water.
- They are so light that they do not sink down to the bottom for a long time.
Applications:
1. It is employed in washing precipitates by adding the wash solution, allowing the solid to settle, and pouring off, continuing the process until free from impurities. If the solid to be separated settles rather rapidly, decantation may be employed to the advantage.
2. In order to separate an insoluble solid from a liquid.
ELUTRIATION:
Def:
- Elutriation is a process for separating particles based on their size, shape and density,using a stream of gas or liquid flowing in a direction usually opposite to the direction of sedimentation.
- This method is mainly.
- used for particles smaller than 1 μm.
LYOPHILIZATION (FREEZE DRYING)
Introduction:
- The process of isolation a solid substance from solution by freezing the solution and vaporizing the ice away under vacuum conditions.
- It is the sublimation from frozen substance.
- It involves triple point of substance.
Triple Point:
- It is the point having the definite temperature and pressure at which the solids, liquids and vapor phases of a chemical entity are able to co-exist.
Triple point - Graph
Steps Involved:
•The process of lyophilization is completed in the following stages.
1-Pre-treatment:
Freezing of solids:
- Before applying the vacuum, he liquid is firstly frozen, this process is called pre-freezing and is done by following ways:
In this method he liquid is taken in a bottle and is rotated slowly, horizontally in a refrigerator bath. So that material freezes as a thin shell (layer) along the walls of the bottle. In this way not only the surface area for sublimation is increased but also heat transfer is increased.
In this method, he bottles are first chilled and then rotated individually in vertical position in the presence of stream of very cold air. So, by this process small crystals of ice are formed. Moreover this process is very rapid.
2-Drying:
After the pre-freezing, the substance is dried there are two types of freezing:
3-Annealing
4-Packaging:
- Amorphous and highly porous
Advantages of Freeze-Dried Products:
- Product is dried without any elevated temperature.
- This process is also good for oxygen and sensitive drugs.
- The product is in porous form, that's why it can be reconstituted rapidly.
- Constitutes of the dried materials remained homogenously dispersed.
- Sterility of the product can be achieved and maintained.
- Due to low temperature enzyme activity and decomposition (hydrolysis) is stopped.
Disadvantages of Freeze-Dried Products:
- Volatile compounds may be removed
- Single operation is very expensive
- The process is slow
- Stability problem associated with individual drugs
Desired Characteristics of Freeze-Dried Product:
The freeze-dried product should have:
Desired Characteristics of Freeze-Dried Product:
Applications:
o Lowers water activity
o Reduces potential for microbial growth
o Biotechnology products
o Biological drugs (proteins, seras etc)