‘per’ means ‘through’
‘colare’ mean ‘to strain’
The process in which a comminuted drug is
extracted of its soluble constituents by the slow
passage of suitable solvent through a column of
In coffee percolation soluble compounds leaves
the coffee and join the water. Insoluble components
remain within the coffee filter.
The process of percolation includes five steps.
Comminution of drug
Imbibition of drug
It is the size reduction of drug usually from
coarse powder to fine powder so that....
To increase surface area
To ensure complete removal of drug
To slow down the movement of menstrum
For uniform packing
Swelling of drug by absorbing menstrum.It is
allowed to stand for 4 hours in a closed container.
It is done to achieve following objectives;
To avoid choking(difficulty in movement)
To remove air
To avoid washing out of fine particles
After imbibition drug is evenly packed into the
The a filter paper is placed on the bottom to support
the column of drug.
Then the moistened drug is placed on the filter
Over the moistened drug another filter paper is
placed having weight on it.
Then menstrum is added. Close the lid if menstrum
After packing sufficient menstrum is added and
covered with lid.
When liquid begins to drop the lower orifice is
Then percolator is set aside 24 hours.
After 24 hours lower orifice is opened and
menstrum is collected with a controlled speed until
¾ of menstrum is collected.
Then more menstrum is added and collected from
the lower orifice so that marc does not become dry.
Then marc is pressed to get extract which is
combined with previous liquid.
Then it is allowed to stand and then it is filtered.
Continuous hot percolation
Continuous cold percolation
This type of percolation is done to get concentrated preparation.
In this method the first portion(about ¾ portion) of percolate
contains maximum amount of active constituent(70 to 80%) is
reserved as such.
The last portion of percolate(about ¼ ) is collected separately
and menstrum is evaporated to get syrupy consistency and
mixed with reserved percolate.
Final volume is adjusted by adding more menstrum.
Usually alcohol is use as menstrum for reserved percolation.
Liquorice liquid extract.
CONTINUOUS HOT PERCOLATION
This process is done for those drugs in which
percolation of menstrum into cellular tissues is very low.
The apparatus use for this process is called as
The menstrum present in the flask is heated and vapours
are taken to a condenser where the condensed liquid is
return to the drug to continue extraction.
Smaller volume of menstrum can be use again and