percolation

Question 1

intro

Answer 1

 Percolation is derived from the Latin word “per” meaning through and “colare” meaning to strain.
 Comminuted (crushed) drug is packed in a column and the solvent is allowed to percolate through it
till complete exhaustion.
 This process ensures maximum extraction.
 Simple percolation or percolation process for tinctures.
 Percolation processes for concentrated preparations such as:
o Reserve percolation process
o Modified percolation process

Question 2

apparatus used

Answer 2

 Conical percolator
 Cylindrical percolator
 Steam jacketed percolator

Question 3

steps involved

Answer 3

The steps involved in this process are:
 Size reduction
 Imbibition with solvent
 Packing in percolator
 Macerating the packed drug
 Collection of solution
 Fresh solvent is added

Question 4

process

Answer 4

size reduction
inhibiton
packaging

Question 5

size reduction

Answer 5

o The drug to be extracted is subjected to suitable degree of size reduction, usually from coarse
powder to fine powder
o To increase the surface area of the drug exposed to the menstruum
o For uniform packing of the percolator
o To ensure complete exhaustion of the drug

Question 6

inhibition

Answer 6

o Powdered drug is moistened with a sufficient quantity of menstruum and allowed to stand for
4 hours in a closed vessel.
o It is done in order to allow swelling of the tissues before packing into the percolator.
o Dry powder if packed into percolator may cause blockage of the percolator.
o It allows entrapped air to escape, dry powder drug would have air entrapped within them, and
this may resist the flow of menstruum and will disturb the packing of the powdered drug.
o Prior to packing of the imbibed drug into percolator uniformity of particle size is ensured by
passing the moistened mass through a sieve of coarse aperture.
o Glass wool moistened with solvent is kept at the bottom to avoid blockage of outlet or tap.
Cotton wool may not be used as after getting soaked it would also create a impermeable mass.
o The imbibed drug is packed in the percolator up to 2/3rd or 3/4th of the volume of percolator.
o Filter paper is placed above this layer and above this a layer of sand is placed in order to prevent
disturbance of top layer when the menstruum is added into the percolator.
o Sufficient quantity of menstruum needs to be added to saturate the material.
o When the liquid starts coming out of the percolator outlet is closed and add menstruum forming
a layer of solvent above the imbibed mass.

Question 7

packaging

Answer 7

o After imbibition the moistened drug is evenly packed into the percolator.
o The packing should not be too tight; it will lead to slow extraction rate. Similarly, loose packing
will allow the menstruum to pass through quickly resulting in incomplete contact with the drug.
o The drug should occupy 2/3rd capacity of the percolator.

Question 8

maceration

Answer 8

o The moistened drug is left in contact with menstruum for 24 hrs.
o During this period, menstruum dissolves the active constituent of the drug and becomes almost
saturated with it.

Question 9

percolation

Answer 9

o It consists of the downward displacement of the saturated solution formed in maceration and
extraction of the remaining active constituents present in the drug by the slow passage of the
menstruum through the column of the drug.
o After collecting 3/4th of the required volume of the finished product or when the drug is
completely exhausted, the marc is pressed.
o Mix the expressed liquid with percolate.
o Add sufficient quantity of menstruum to produce the required volume and then filter.
o E.g. tincture of belladonna, compound tincture of cardamom, strong tincture of ginger.

Question 10

advantages

Answer 10

 More complete extraction of constituents
 Shorter processing time
 Increased flexibility in processing

Question 11

disadvantages

Answer 11

 Fine powders and materials such as resins and plants that swell excessively (e.g., those containing
mucilages) can clog the percolator.
 If the material is not distributed homogenously in the container, the solvent may not reach all areas
and the extraction will be incomplete.
 Incompaticbility of percolation with certain herbs
 Additional complexity in processing

Question 12

complete extraction test

Answer 12

 Take a few ml of the last percolate and evaporate to dryness, it no residue remains - it shows that the
drug is completely exhausted.
 Specific chemical tests may be performed on the percolate for the drugs containing alkaloids,
glycosides, tannins, resins or bitter constituents.