This document discusses various percolation processes used to extract drugs, including simple percolation, reserve percolation, and continuous hot percolation. Simple percolation involves imbibing powdered drug with menstruum, macerating for 24 hours, then slowly percolating menstruum through the drug column. Reserve percolation collects part of the percolate, evaporates it to an extract, then dissolves the extract in the reserved percolate. Continuous hot percolation uses a Soxhlet apparatus to continuously treat a sample with recondensing solvent over hours or days for improved extraction.

1. PERCOLATION PROCESS
Dr Kusum Akki
Associate professor
KLE College of Pharmacy
Hubballi

2. Percolation Processes
The various percolation processes used for the extraction of
drugs are:
1. Simple percolation or petroleum process for tinctures.
2. Percolation processes for concentrated preparation :
• Reserve percolation process
3. Continuous hot percolation or soxhelation

3. Simple percolation
Three types of percolators are used.
1. Conical Percolators: The percolator is made of glass or of metal .It is conical in
shape .
2.Cylindrical Percolaters: The percolator is cylindrical in shape i.e. Upper and lower
diameters are same. When a higher concentration of alcohol or any other volatile
solvent is used as menstruum a cylindrical percolator is preferred.
3. Steam jacketed percolator: When percolation is carried a higher temperature ,in
order to increase the solvent action of the menstruum, the percolator is heated by
steam.

4. METHOD
Simple percolation process is used for the preparation of tincture. There are three
stages in the official method for the preparation of tincture :
A) Imbibition
B) Maceration
C) Percolation
A) Imbibition : The powdered drug is moistened with sufficient quantity of
menstruum and allowed to stand for 4 hrs in closed vessel. Pack the moistened drug
into percolators & add sufficient quantity of menstruum to saturate the material.
When liquid starts coming out from outlet of percolators, the outlet is closed. Then
the sufficient quantity of menstruum is added in order to leave a layer above the drug.

5. B) Maceration : The moistened drug is left in contact with menstruum for 24 hrs.
During this period ,the menstruum dissolves the active constituents of the drug and
becomes almost saturated with it.
C) Percolation: It consist of downward displacement of saturated solution formed in
maceration and extraction of the remaining active constituents present in the drug by
slow passage of the menstruum through the column of the drug . After collecting ¾ of
the required volume of the finished product or when drug is completely exhausted, the
marc is pressed. Mix the expressed liquid with percolate. Add sufficient quantity of
menstruum to produce required volume and then filter.

6. Packing of the percolator

7. Steps in percolation
1. Size reduction: The drug to be extracted is subjected to suitable degree of size
reduction, usually from coarse powder to fine powder.
2. Imbibition: During imbibition the powdered drug is moistened with a suitable
amount of menstruum and allowed to stand for four hours in a well closed
container.
3. Packing: After imbibition the moistened drug is evenly packed into the
percolator.
4. Maceration: After packing sufficient menstruum is added to saturate the material.
The percolator is allowed to stand for 24 hours to macerate the drug.
5. Percolation: The lower tap is opened and liquid collected therein is allowed to
drip slowly at a controlled rate until 3/4th volume of the finished product is
obtained.

8. RESERVE PERCOLATION PROCESS
 In this process, a part of the percolate, generally 3/4th the volume of the
finished preparation, is reserved.
 Then the percolation process is continued till the drug is completely
exhausted.
 Then the percolate is subjected evaporation or distillation to convert it
into a soft extract.
 This soft extract is dissolved in the reserve portion of the percolate &
then sufficient menstruum is added to produce the required volume.

9. CONTINUOUS HOT PERCOLATION OR SOXHELATION
SOXHLET APPARATUS A Soxhlet extractor is lab equipment designed
for processing certain kinds of solids. These devices allow for continuous
treatment of a sample with a solvent over a period of hours or days to
extract compounds of interest. Typically, a Soxhlet extraction is only
required where the desired compound has a limited solubility in a solvent,
and the impurity is insoluble in that solvent.
It was invented in 1879 by a scientist named Franz von Soxhlet. It was
first invented for the quantification of fat in the milk. Then it has been
frequently used for the extraction of lipids in agricultural chemistry.

10. https://www.researchgate.net/publication/25
1753895_Solvothermal_removal_of_the_org
anic_template_from_L_3_sponge_templated
_silica_monoliths

11. Soxhlet extraction unit is a fully automated system, based on soxhlet
apparatus for fast extraction of soluble matter from a wide range of
matrices
Advantages:
 The material is extracted continuously, i.e., the solvent saturated in
solubilized metabolites empties into the flask, fresh recondensed
solvent then re-extracts the material in the thimble.
Disadvantages:
 Physical character of the drug
 Solvents
 Chemical constituents of the drug